APPEAL COURT, HIGH COURT OF JUSTICIARY
 HCJAC 58
OPINION OF THE COURT
delivered by LORD WHEATLEY
in the Referral by the
Scottish Criminal Cases Review Commission in the case of
BRIAN WILSON AND IAIN MURRAY
HER MAJESTY'S ADVOCATE
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For the First Appellant: Lamb, Connor; Drummond Miller, W.S.
For the Second Appellant: Shead, Mason, BCKM Solicitors
For the Respondent: Stewart, A.D.; Crown Agent
18 June 2009
 Brian Wilson and Iain Murray were charged together on an indictment which read as follows :-
"On 22 May 1986 in Garscaddan Woods, Glasgow, near Chesters Road
(1) being persons under the age of 21 years, namely being 18 and 17 years old respectively, you did commit with each other a homosexual act, namely an act of gross indecency and did masturbate each other otherwise than in private CONTRARY to the Criminal Justice (Scotland) Act 1980, Section 80(7)(a) and (c);
(2) you did assault Alison Mary Violet Chambers also known as Murray, 6 South Dean Road, Glasgow, and did repeatedly seize hold of her and pull her to the ground, strike her on the body, hold her down, forcibly remove her clothing, lie on top of her, fondle her breasts, place your hands over her mouth and around her neck and compress her neck therewith, force her legs apart and repeatedly attempt to rape her, place and tie a brassiere around her neck and strangle her therewith and you did murder her."
 The trial took place between 23 September 1986 and 10 October 1986 at the High Court in Glasgow. On 10 October 1986 the jury found the appellants not guilty of charge 1 (the Crown had not sought a conviction on that charge), and guilty by a majority verdict of charge 2 under deletion of the words "strike her on the body", "forcibly", and "repeatedly" where it last occurs in the charge. Brian Wilson, who is the first appellant, was sentenced to detention for life in a young offender's institution and Iain Murray, the second appellant, to detention for life under the direction of the Secretary of State.
 Alison Murray, who was aged 20 years at the time, was killed at approximately 10pm on 22 May 1986. She had apparently gone for a walk in Garscaddan Woods (otherwise known as the Bluebell Woods). She was a fourth year biology student who was due to sit her final exams in a week's time, and she had gone for a walk to clear her mind. There was no eyewitness to the murder, nor was there any forensic evidence. There was no doubt that she had been murdered. She had not been raped. The post mortem examination showed that she had died of ligature strangulation as a result of her brassiere being knotted tightly round her neck. Alison Murray was the half sister of the second appellant.
 Alison Murray's body was found lying on its back more or less in a line up and down near the bottom of some steeply inclined ground among bramble bushes. Her head was inclined to the right and both her arms were extended directly above her head. Both legs were outstretched, down towards the road. The upper part of her body was pointing at a slight angle towards the top of the slope, where there was a path through the woods. She was completely naked apart from a pair of white socks which were dirty and grass stained. Her hands were still in the sleeves of her anorak, and on the slope just above her and on top of the anorak was a blue jersey. Lying over her right thigh was a pair of light blue denims which were turned inside out. There were coins on the ground underneath the denims. To the right of the denims was a pair of pink underpants, and hanging from a twig just above the anorak was a blue and white vest turned inside out. There was a pair of training shoes near her left foot. Around her neck was her brassiere, and intense signs of asphyxia were visible in the face. There were numerous other scratches and bruisings on the body, the scratches being particularly noticeable on the girl's back. There was no indication that sexual intercourse had occurred. Her gold watch had not been taken, there was money scattered about on the ground, and her credit cards were found in her purse or her pocket.
 The body of the girl was found by three children, who called three other children and later some adults to see what they had discovered. These witnesses apparently observed that the girl, naked apart from her socks, was lying on her back with her hands above her head. It was seen that there was something round her neck, her jacket was on her arms, and the ground between the footpath and where she was found was "all flattened out." An intensive police investigation then took place over a period of three and a half weeks. The police believed that more than one person was involved in the murder and that they probably belonged to the local Drumchapel community. Many people were interviewed and house to house enquiries were carried out. The assistance of Radio Clyde was obtained and it was disclosed in a broadcast that the girl had been strangled with her brassiere. It also appears that those who had seen the body in the wood told relatives and friends what they had observed in general terms, and that all members of the Murray family were told by the police that the girl had been murdered, that she had been sexually assaulted but not raped, and that her body had been almost completely naked. About three weeks after the murder, the appellants, who had earlier given statements to the police in the course of the inquiry, were again interviewed and are said to have made statements admitting their guilt, which indicated a knowledge of the crime that could only have been available to the perpetrators. In the event, the Crown case at the trial depended entirely on these statements. The history of these various statements is as follows.
Statements by Brian Wilson and Iain Murray.
 The first statement given by Iain Murray was taken on 25 May 1986 some three days after the murder. He said that he had been with Brian Wilson on the day of the murder and that they had walked up to Station Road, Drummore Road and then along to Bearsden and back "the other way." The first statement by Brian Wilson was taken on 27 May 1986. He said that he had gone for a walk with Iain Murray around Kinfauns Drive, which did not involve walking to Station Road or Bearsden. The police then took a second statement from Brian Wilson because of these discrepancies, and he gave an account which at first coincided with that given by Iain Murray, but was then changed to a slightly different story.
 On 15 June 1986 the police wished to interview both appellants again to clarify these discrepancies and to see if they could shed any more light on the crime. Brian Wilson was interviewed at Clydebank Police Station and at the same time Iain Murray was also interviewed at Drumchapel Police Station. At that time there were no tape recording facilities in either Clydebank or Drumchapel, although there were such facilities available at Maryhill Police Station in Glasgow. Both appellants were being interviewed as witnesses, and not as suspects.
 Brian Wilson was interviewed by Detective Sergeant Weir and Detective Constable Poole at 12:30pm and gave a statement, which he signed. In it he gave a detailed account of his movements on the evening of the murder. In particular he mentioned that he and Iain Murray had seen two men, whom he described in detail, at the pavilion in Drymen Road. He also mentioned that he had seen two girls on a bench nearby. After about an hour they returned to Brian Wilson's home. Brian Wilson described the clothes that he and Iain Murray had been wearing. D.S. Weir noted that for the first time Brian Wilson mentioned seeing other people at particular locations, and went to another room to check this account against those of other witnesses. Then, at 1.30pm, Brian Wilson was taken home to uplift the clothes he had been wearing on 22 May 1986. On his return to the police station at 2:30pm, he was left with D.C Poole, while D.S Weir went to the incident room to check further details. He was there given information that Iain Murray was at Drumchapel Police Station and had admitted to being homosexual. D.S. Weir then went back to Brian Wilson and questioned him about the nature of his friendship with Iain Murray, and Brian Wilson, at or just before 2.40pm, then admitted that he also was a homosexual, and that he had had sex with Iain Murray regularly in his room or in the Bluebell Woods. He also told D.S Weir and D.C Poole at that time that he had been in the wood on the night of the murder with Iain Murray. D.S. Weir then telephoned D.C. Dickov at Drumchapel Police Office with this information.
 D.S Weir then received a telephone call from D.C Dickov at Drumchapel Police Office at 3.20pm, telling him that Iain Murray had also admitted to having been in the wood between 9.15pm and 9.20pm on the night of the murder and that on that evening they had been masturbating each other, and further that Iain Murray had said that they had seen his stepsister, Alison Murray. D.S. Weir then questioned Brian Wilson further on whom he had seen in the wood, having in mind that Iain Murray had said that he had seen the victim. He did not consider Brian Wilson to be a suspect at that stage. At 4:15pm Brian Wilson's mother telephoned the police station and Brian Wilson made it known that he did not want his mother to be worried about him. After taking instructions from Detective Chief Inspector Tennent, D.S. Weir asked Brian Wilson to sign a voluntary attendance form at about 4.30pm. D.S. Weir then continued to interview him and at 4.40pm Brian Wilson admitted that he and Iain Murray had engaged in sexual activity in the woods on the night in question. However, he gave an unsatisfactory answer to questions about whom he had seen in the wood and D.S. Weir began to suspect that Brian Wilson was lying. He was apparently looking worried and quiet, and he was given a cigarette and some Irn-Bru. D.S. Weir telephoned D.C.I. Tennent at Drumchapel to say that he was going to make Brian Wilson formally a suspect for the murder, and returned to caution him. Brian Wilson did not respond immediately to the caution, but then made the following statement:-
"Aye. She met Iain and I and they started arguing and I think she saw us. We were at the top path and we pushed her. I tried to strangle her with my hands and she fell and I think she hit a tree. She never moved and I was going to walk away. She came around and started arguing with Iain again and she was still on the ground. Iain said to me 'you want to screw her?' I started to walk away and he called me a shitbag so I went back and Iain held her down on the ground and started to take her clothes off. She seemed to be sort of unconscious and couldn't struggle. I had sex with her and she was completely stripped. I couldn't have sex with her so we put her jacket back on and I put her bra on her neck and strangled her more. Iain put the anorak on. We left her and walked away. We got nervous and started running down the path to the lane and then we stopped running because we seen somebody on the road. We walked home."
 On 15 June 1986 Iain Murray was questioned at Drumchapel Police Station, initially on another matter, by Detective Constables McKie and Dickov. He attended the police station at about 11.15am and signed a voluntary attendance form in respect of an allegation that he had had sexual intercourse with Denise McMillan, who was aged 15 years, and that he had also had a homosexual relationship with her brother, Clark McMillan. He denied both these allegations. It is unclear how long the interview in respect of these matters took. Iain Murray was then interviewed at about 1.20pm about the statement he had given to the police describing his movements on the night of the murder. At about 2.45pm D.C. Dickov received a telephone call from D.S. Weir at Clydebank informing him that Brian Wilson had admitted to being in the wood between 9.15pm and 9.20pm on the night of the murder with Iain Murray. Iain Murray was told about this at about 2.50pm. Iain Murray then stated:-
"Look, that's right enough. Brian asked me to go up to the wood for a bit of fun. I told him no, but he asked again and I said OK. We went into the Bluebell Wood up near the fence and the rest of the houses at the top and we lay down on the grass. We both had our trousers down and playing with each other. We were wanking each other. My sister walked along the path."
At that point, the two detectives were joined by a third officer, and Iain Murray continued:-
"My sister walked along the path and I tried to hide in case she seen me. She walked along the path and we got dressed."
"I caught up with her and asked her where she was going she said 'Out for a walk.' I was frightened in case she had seen me."
 At this point D.C. Dickov informed D.C.I. Tennent at Clydebank of Iain Murray's statement and awaited his arrival. He also asked Iain Murray whether he wished the services of a lawyer, but this offer was refused. He was told to say nothing further until the arrival of D.C.I. Tennent. When D.C.I. Tennent arrived at about 3.50pm Iain Murray was reminded that he was still under caution, and he repeated his story to the effect that he and Brian Wilson had been out for a walk and went up to the Woods for some fun, that they had seen his sister, and that he was concerned in case she had seen them. At about 4.45pm, following the admission by Brian Wilson to D.S. Weir that he and Iain Murray had engaged in sexual activity in the woods, D.C.I. Tennent became aware that Brian Wilson was to be treated as a suspect. D.C.I. Tennent then resumed his interview with Iain Murray and indicated that he did not believe what he had been told. He called Iain Murray a liar. At that point it was noted that Iain Murray became visibly upset, his hands were fidgeting and his eyes swollen. He then stated:-
"I'm ashamed of what I did to my sister. She came along and caught us playing with each other. She said, 'Iain how could you.' We got up and pulled our trousers up. We ran after her. Brian grabbed hold of her and I pulled her to the ground. I didn't know what to do. I was frightened to tell my parents. I mean in case she told my parents. She was on the ground on her back and I ran over. Brian was on top of her and I grabbed hold of her wrists from behind and I pulled them down. She was struggling but wasn't saying anything. Brian started to take her trousers and pants off. He opened his own trousers and lay in between her legs. I think he had a go at her. I unfastened her jacket and pulled it off. At this point Alison managed to break free from me and push Brian off. She got up and started to run but we caught her. Brian pulled her to the ground again and I got on top of her. I didn't really have a go at her because I didn't open my trousers. Brian was holding her wrists and he undid her blouse and bra. I played with her breasts, sort of fondled them. She managed to push me off a bit and half got up. Brian went on top of her again. I was holding her arms above her head. I pulled off her blouse and bra. She started screaming very loudly, before that she was just struggling and moaning.
I put my hands round her throat and tried to strangle her. I'm no sure if Brian tried to strangle her at that time but he did have his hands at her throat. I was panicking by this time because she was screaming and struggling. This went on for a while and she went quiet. I pick up her bra, put it round her neck and strangled her."
D.C.I. Tennent then asked Iain Murray what he did then. He continued:-
"We decided to hide the body so we put her jacket back on and started to pull her down the hill. We stopped and ran away. We were arguing with each other going down Chesters Road."
D.C.I. Tennent then asked the second appellant:-
"How did you leave your sister's body?"
Iain Murray then asked for a piece of paper and sketched the body as it was left. Iain Murray was asked if he would indicate where the body was in relation to the fence at the locus and he did so accurately.
Caution and charge of Brian Wilson and Iain Murray
 Later that day, at about 7.10pm Brian Wilson and Iain Murray were cautioned and charged together with the murder of Alison Murray at Clydebank Police Station. The charge included allegations of pushing her to the ground, removing her clothing and raping her. Brian Wilson replied "Aye." and Iain Murray said "Yes." They were then asked if they had anything to say regarding the charge and Brian Wilson replied:-
"There is nothing more I can say, we did it. She caught us playing with each other and we strangled her."
Iain Murray replied:-
"Just the same, I done it with him. I just fondled about her breasts while Brian was holding her. He then had sex with her while I held her down. I was scared she would tell my parents that me and Brian were wanking each other."
 According to the police evidence, both Brian Wilson and Iain Murray then said that they wished to make voluntary statements. The duty solicitor, Hugh Murphy, was contacted, and arrived at Clydebank Police Office. He advised each of the appellants separately, in the clearest and most emphatic terms, that they should not make voluntary statements. Brian Wilson took this advice, but Iain Murray insisted on making a statement.
 The evidence as to the procedure which at that time was adopted when an accused person wished to make a voluntary statement was that two police officers would be summoned from another police station. Those officers would have no knowledge of anything to do with the case. The two policemen who were summoned (at about 7.45pm) in the present case were D.C. McCrossan and D.I. MacKay. The statement was taken between 8.55pm and 9.38pm. The first part of it was written by Iain Murray himself, signed by him and countersigned by the officers. It read as follows:-
"I have been cautioned by Detective Inspector MacKay - I am not obliged to make any statement and that any statement I care to make will be taken down in writing and can be given in evidence in any proceedings which may be taken against me. I have also been advised that I can have a solicitor present. I do not wish a solicitor to be present."
The voluntary statement was in the following terms:-
"Me and Brian Wilson went out that night about 9 o'clock on a Thursday about three and a half weeks ago. We went out just for a walk and we were walking past Pinewood School then Brian asked if I wanted a bit of fun. I said no and he said 'Aw come on'. I said 'OK'. So me and Brian went into the Bluebell Woods about quarter past nine. Then we started playing with each other that is giving each other a wank. Then my sister Alison, stepsister she is, she came by and seen us. Then Brian grabbed her and pulled her down. Then I took a hold of her arms and he started to undress her. He took her trousers and her pants off and then he got on top of her. She started fighting and I let go of her arms. Then she knocked Brian off and then she tried to run away, but Brian got a hold of her again and pulled her down. Then Brian started to take her jacket off and then I took it off. Then we opened her blouse. Then Brian started holding her arms. I got on top and started playing about, fondling her tits. Then she sat up again and she started screaming so I put my hands around her neck and strangled her. Then I used her bra and put it round her neck. Then when she shut up we just panicked and ran away. I am sorry now for what I have done. I didn't mean to kill her. That's all."
 Iain Murray and the two policemen signed the statement. It was also read over to him and he signed:
"This statement has been read over to me and it is true. I do not wish to make any changes or say anything more."
Statements made after caution and charge.
 On 15 June 1986 at about 7.30pm the first appellant, Brian Wilson, had a meeting at Clydebank Police Station with his parents Robert Wilson and Jessie Wilson. D.C. McKie was present. In terms of his Crown statement and defence precognition, D.C. McKie stated:
"The accused Wilson then stated he would like to speak to his parents with one officer and I then remained in the room with the accused Wilson and his parents. He then stated, 'I didnae do it." His mother Mrs Wilson then said, 'but why did you tell the police you had done it?' The accused Wilson then said, 'I told the police because they kept asking me questions and I had to tell them I did it.'
Mrs Wilson then said, 'But why?' The accused Wilson then said, 'I don't know'
Mrs Wilson then said, 'How did the police make you? They didn't mistreat you did they? So why did you say that?'
The accused Wilson then said, 'They kept questioning me, I was under pressure to admit it.' Mrs Wilson then said, 'But did you murder the poor girl? She didn't deserve that.'
The accused Wilson then said, 'We did murder her. She caught us playing with each other.'
Mrs Wilson then said, 'Why did you say that you didn't do it?'
The accused Wilson then said, 'The lawyer told me to say that I didn't do it and I had admitted it because they had put pressure on me'.
The accused Wilson then lowered his head and said no more.
Detective Chief Inspector Paul then entered the room when I opened the door and the accused Wilson then said to his parents, 'I did it.'"
This conversation was recorded by D.C. McKie in his notebook.
 It appears from the Court minutes of the trial that D.C. McKie gave evidence. Mrs Wilson subsequently also gave evidence, and an objection was taken to her answering questions about the conversation, on the basis that it had been initiated by a police officer suggesting to Brian Wilson that he should tell his parents about what had happened. The objection was sustained. Nevertheless, it appears from exchanges between counsel and the trial judge, after the jury had retired, that D.C. McKie's evidence as to the conversation as recorded in his notebook had been led before the jury, and it can be inferred from the minutes that this evidence had been led from him without objection.
 On 16 June 1986 Brian Wilson underwent a medical examination by a Police Medical Officer, Doctor Gourley at Clydebank Police Office at about 12.30am. His findings suggested that Brian Wilson had engaged in recent homosexual activity. The first appellant fainted in the course of the examination.
 On 17 June 1986 at Maryhill Police Office, Glasgow, D.C. Hutcheson was involved in conducting an identification parade at about 6pm. Iain Murray, the second appellant, indicated to him that he wished to speak to his father. D.C. Hutcheson agreed to this and subsequently recorded the conversation. Part of the conversation was in the following terms:-
 Mr Murray senior said:-"There's a hundred questions I want to ask you. First I need to know if you done it. Did you do it?" The second appellant replied "Yes." Later on Mr Murray Senior asked the second appellant "Who done it?", and the second appellant said "I done it and that's it." Then, the appellant's father said:- "If you done it you'll plead guilty to it, you're no bringing the family through the courts, your mother cannae stand it." The appellant replied "It's alright, I'll plead guilty". After this conversation was completed, D.C Hutcheson went outside and wrote down his record of what had been said in his notebook. He then told Iain Murray's solicitor, Gerald Hanretty, who was waiting to see his client, of the contents of this conversation. Mr Hanretty then asked D.C. Hutcheson to leave the room, and Iain Murray then repeated his admission to his solicitor. In particular, Mr Hanretty, although his memory of events is not perfect, appears to have been quite clear in his understanding that the second appellant was "holding up his hands" to the murder and that there would be no trial.
 Six days later at his second judicial examination Iain Murray specifically admitted that he had made this statement to his father in the presence of D.C. Hutcheson. However according to the transcript of evidence, Iain Murray's counsel at trial, presumably on instructions, put it to D.C. Hutcheson that he was lying when he spoke to this admission by the second appellant to his father. The appellant's father in evidence said that he could not remember the conversation but he did recall that two days earlier his son had made another admission to him of his guilt.
 On 19 June 1986 both appellants were judicially examined. Brian Wilson denied the murder. His position was that the admissions he had made were false. He accepted that he had replied to caution and charge on 15 June 1986 in front of Chief Inspectors Paul and Tennent, D.S. Weir and D.Cs. Dickov, McKie and Poole in the terms quoted earlier in this opinion. In addition, Brian Wilson accepted that he had made certain admissions in front of D.S. Weir and D.C. Poole at Clydebank Police Station. His explanation for making these admissions was that he had been placed under pressure:-
"They kept, like, asking me a question and whenever I says an answer they says I was a liar. And, every time they asked me the question they kept saying liar all the time. And, like, they kept repeating theirself, they kept repeating the question. And then I gave the answer and they kept saying liar every time I says it."
Iain Murray was judicially examined on two occasions on 19 June 1986 and on 23 June 1986. At the judicial examination on 19 June 1986, the second appellant denied the charge of murder. He said that the admissions he had made were false. He accepted that he had responded to caution and charge on 15 June 1986 at Clydebank Police Station in front of the same police officers as his co-accused in the terms cited earlier in this opinion. He claimed that he had said this because he was scared. He also accepted that he had made the voluntary statement to D.I. MacKay and D.C McCrossan on 15 June 1986. He said that he was scared and that:-
"They kept asking me the same questions all the time and every answer I gave them they kept calling me a liar."
However, these allegations about the way in which this statement was taken were not repeated at the trial, and it seems, on the contrary, it was conceded that this interview was conducted with complete fairness. Iain Murray also agreed that he had made certain admissions at Drumchapel Police Station in front of D.Cs. Dickov and McKie; again his explanation for making these admissions was that he was scared. Finally, at the judicial examination on 23 June 1986 the second appellant was asked about admissions he had made to his father in the presence of D.C. Hutcheson on 17 June 1986 at Maryhill Police Station. His position was that he had made these admissions but that they were false, because he was scared by the police and the fact that there was one police officer still in the room when he spoke to his father led him to carry on saying he was guilty.
Further issues concerning the statements
 Three further matters appear to have a bearing on the claims made by the appellants that they made these various incriminating statements only under pressure. First, it appears from the decision of the court in the subsequent criminal appeal that counsel who presented the appeal for both appellants, and who had both appeared for the appellants at the trial diet, were instructed at the appeal to depart from the position that the statements had been made under pressure. Secondly, in a report dated 4 September 1990 for the Preliminary Review Committee of the Parole Board (a committee which at that time determined the length of sentence which particular prisoners require to serve), the prison governor who prepared the report recorded Brian Wilson's attitude to the offence as follows:-
"On the day of the offence Wilson states that he and Murray were walking through the streets in Drumchapel where they met their victim. She joined them and all three walked into the woods nearby. Murray and his stepsister who were walking ahead of him started an argument about something that had happened in their home. The argument began to get heated and Murray started assaulting his stepsister."
At this point Wilson said:- "I panicked and walked away." He states he did not know Alison Murray was dead until he saw Iain Murray the following day. When questioned how she died, he said:-
"I didn't know she was stripped and strangled until the court case."
 It appears from other material that this report may have been prepared by Prison Governor George Mitchell. In subsequent reports it is said that Brian Wilson consistently denied seeing or being near the victim on the night of the murder. He admitted to being in the vicinity of the crime with his co-accused, but categorically denied involvement in the offence. In the report for the preliminary review committee on 5 October 1992 it was recorded that Brian Wilson was:-
"Still devastated and resentful when I questioned him about the confession to the police, he explained how he was interrogated for seven and a half hours, how the police put words into his mouth and how he finally confessed through police pressure..."
 Third, in a precognition (Appendix C-16) taken at Longriggend when he was on remand, Iain Murray indicated that he knew that the victim had been strangled with her own brassiere and that his father had pointed out to him where the body was found. He said that he had only made his confession after he had given in to pressure from the police. When he was asked how he came to draw a sketch of the body where it was found, he said that he just drew "any old thing. Just off the top of my head."
 In their numerous statements about how they came to make these confessions, the accounts of both appellants varied in a number of minor respects. At the judicial examinations, for example, the appellants in similar terms indicated that they had confessed as a result of being scared, and because of the pressure imposed upon them by the police, and by repetitive questioning. In the course of his evidence (Appendix A1-12), Iain Murray indicated "the police suggested words, made me repeat them and then wrote them down and then made me say them again to senior officers." On another occasion he said that police officers put words into his mouth. In speaking to Gerry Rooney in 1998 (Appendix B2:13) he indicated that the tactics employed by the police consisted of piling up small pieces of information which they provided and asking him to affirm these. In Appendix B2:14 it is said that there was a lot of shouting, intimidation and accusation, and that the confessions were made up of a series of answers to questions. On one occasion Brian Wilson said that he simply made the statement up and implied that the police had only corrected occasional details. On another occasion Iain Murray made it clear there was no question of being fed information; he was just embarrassed about the allegations. We draw no inferences from these various accounts.
Position of the defence at trial
 In these circumstances the evidence against the appellants at the trial was based entirely on these various statements which they were said to have made, incriminating themselves. The defence position was that the statements should not be accepted because they were not obtained fairly and they were not true. It was submitted that the statements were induced by unfair methods. In the case of Brian Wilson it was argued that there had been persistent questioning, at the end of which he was prepared to agree to what was being put to him. In Iain Murray's case, his counsel said that his client was "fitted up" and eventually was induced under pressure to reply to and say the things which the police wanted him to say. Subsequently, further particulars of the claim that pressure was put on the appellants have emerged. In particular, it is maintained that pressure was put upon Brian Wilson to admit that he was homosexual, and that he was described by police officers as such in derogatory terms. It is also said that at one point during his police interview he was pushed or thrown to the ground. However, perhaps the most important feature of the defence position at the trial was that it was apparently not suggested that the appellants had come by their knowledge of the details of the offence from information given to them by the police; rather, it was claimed that all of this information was public knowledge, a position different from that maintained by the appellants subsequent to their arrest.
The initial appeals
 Following their conviction both appellants appealed. Their grounds of appeal were in broadly similar terms and were as follows.
"1. The learned trial judge misdirected himself in law by rejecting the submission of no case to answer in respect that there was insufficient corroboration of alleged voluntary statements made by the appellants.
2. The learned trial judge misdirected the jury in failing to direct them that there was insufficient corroboration of the said voluntary statement in respect that the special knowledge alleged to have been displayed in the detail of the statement should be known not only to the police and the perpetrator or perpetrators of the crime but also to members of the general public."
"1. The presiding judge misdirected himself in law in that he wrongly allowed an admission by the appellant to his father, after the appellant had been cautioned and charged, to be admitted in evidence.
2. The presiding judge wrongly repelled a submission of no case to answer, there being no evidence to corroborate admissions by the appellant.
3. The presiding judge misdirected the jury in that he failed to direct them that the Crown had failed to prove that the facts contained in the statements made by the appellant could only have been known to the perpetrator of the crime and the police."
The first ground in the note of appeal on behalf of Iain Murray does not appear to have been argued. Following submissions, the Appeal Court delivered an opinion which is now reported as Wilson v H.M Advocate 1987 SCCR 216. Having described the facts and circumstances leading up to the desire on the part of the investigating officers to clarify the statements made by the two appellants, the opinion of the court reads in part as follows:-
"On that day Murray was taken into custody and to Drumchapel Police Station in connection with allegations that he had sexual relations with a girl who was under sixteen years of age. At about midday, at the request of the police, Wilson went to Clydebank Police Station to discuss his earlier statements further. The remarkable thing is that each, in separate police stations, then made a detailed confession of guilt of the murder which, subject to quite insignificant differences of detail, was identical. The essential details disclosed in each of the accounts given by the appellants tallied precisely with what had been found at the scene of the crime. The circumstances in which these detailed confessions were made - and there is now no suggestion that they were unfairly obtained - and the contents of each confession are described at length by the trial judge in his charge to the jury...
...the jury were in particular directed that it was for them to decide whether the only reasonable explanation for the knowledge of the details of the crime disclosed in each of the confessions made in different police stations was that the appellants were the perpetrators of the crime. The submission made by counsel for each respondent in different language was that having regard to the widespread knowledge of the details of the murder, the case against the appellants should not have been allowed to go to the jury at all. In other words, it was said that the trial judge should have acquitted each appellant at the end of the Crown case upon the ground that the evidence of the accuracy of the appellants detailed knowledge of the crime, contained in the statement of each of them, was in the special circumstances of this case incapable of being regarded as providing the corroboration required by law...
... In this connection the only reported case to which reference was made was McAvoy v H.M Advocate in which Lord Hunter at 1982 SCCR p. 272 said this:
'I am satisfied that in the circumstances disclosed to this court the ratio of such cases such as Connolly v H.M Advocate 1958 SLT 79 and Manuel v H.M Advocate 1958 J.C. 41 applied. I refer in this connection to the charge of the learned sheriff, which in my opinion dealt very adequately with this aspect of the case. I would only add that it is not in my opinion necessarily fatal to application of the ratio of the cases to which I have referred that persons other than the accused had become aware of the facts and circumstances used as corroboration of a detailed confession before the confession itself had been made. This, however, does not mean to say that passage of time between the date of the crime and the date of a detailed confession is of no moment, since such a delay might in some circumstances make it more likely that an accused person had acquired his knowledge of detail not as a perpetrator of the crime or offence but as a recipient of information from other sources.'
In our opinion the trial judge would not have been entitled in this case to sustain a motion that there was no case to answer. There was, in law, quite sufficient evidence capable of providing corroboration of these remarkable, almost identical, confessions made by each appellant at separate police stations to the appalling murder of the half sister of Murray. Each provided an identical and powerful motive for the dreadful crime, and was redolent of having been made by someone who had been present when the crime was committed. The evidence of the coincidence between the details of the killing which each confession disclosed, and what was found after the event, was sufficient in law for corroborative purposes if the jury were prepared to find that the accurate knowledge of the crime revealed in the statements of each appellant was his own knowledge as one of the perpetrators. It was not for the trial judge to evaluate the weight which should be given to the circumstance that by 15th June 1986 many people knew or had heard of many of the details of the crime. That was essentially a matter for the jury to consider under the proper directions which were given and that, indeed, is precisely what Lord Hunter had in mind when he said what he did in McAvoy."
The Appeal Court accordingly rejected the appeals of both appellants.
The current appeals
 Following the rejection of their appeals in 1987, the appellants referred their case to the Scottish Criminal Cases Review Commission, who then undertook a lengthy and detailed investigation. In about 2004, the case was referred back to this court on various grounds. In respect of Brian Wilson, the first (and most significant) ground of appeal in terms of the Commission's reference was in essence that his admissions to police officers were unreliable and were obtained by means of unfair pressure at a time when he was vulnerable to such pressure in terms of his psychological makeup. Brian Wilson's second ground of appeal was to the effect that the trial judge misdirected the jury. In his charge, the judge had said:-
"I think that you might also be inclined to think that what has been put by the defence in this case really amounts to some sort of collusion amongst up to ten different policemen, pretty well all the policemen involved".
It is suggested that in presenting this sort of choice to the jury, the trial judge went too far in that he gave the jury the choice between accepting the police evidence as credible and reliable as a whole, or rejecting it on the basis that their evidence amounted to a collusion to pressure the first appellant into an admission without regard to its veracity. It is said that this approach was not justified on the evidence, was unfair to the first appellant and amounted to a material misdirection which has led to a miscarriage of justice.
 The third ground of appeal for the first appellant was to the effect that when the appellants were charged with murder, they were charged in each others' presence. They were cautioned in standard form. However it is said that this procedure should not have been adopted and was manifestly unfair. The police officers were either thoughtless or it was a deliberate ploy to create a situation where the accused were young, ought to have been seen to be vulnerable, their interviews had not been tape recorded and they were to be charged with a most serious crime. In those circumstances it is submitted that they ought to have been charged separately. If they had to be charged together, they ought to have been advised that anything said by one in the presence of the other could be evidence against that other.
 For Iain Murray, the first ground of appeal is along similar lines to that of his co-appellant. It is said that he was convicted of attempted rape and murder. It is pointed out that the Crown case depended on the jury accepting as credible and reliable the admissions he was said to have made to police officers. Professor Gudjonsson's opinion was that he had reservations about the reliability of those confessions. Had Professor Gudjonsson's views been before the jury, it would have been of material assistance to the presentation of the appellant's defence, given that the appellant's denial of the truth of the admissions was unsupported. If the jury had accepted the expert evidence they would have been bound to acquit.
 The second ground for Iain Murray is essentially similar to that of his coappellant and is in the following terms:-
"2. The trial judge misdirected the jury on the approach that should be taken to the defence case. He suggested that, if the appellant's position that he had been 'fitted up' were the truth, then it represented 'some sort of collusion amongst up to ten different policemen'. He went on to suggest that there had been a failure on the part of defence counsel to put that position to two of the senior police officers who had been called as witnesses. ..."
The direction given did not reflect the approach taken by the defence at the trial. In any event it was apt to undermine the appellant's position by suggesting that the matter should have been pursued in cross examination when it was not. The way in which it was expressed suggested that the defence had to go further than was necessary to raise a reasonable doubt in relation to the appellant's guilt."
 Both appellants subsequently lodged a supplementary ground of appeal. This ground was in essence that because the nature of the defence was that the confessions had been unfairly obtained by means of inappropriate or improper pressure, the trial judge should have held a trial within a trial, and rejected the confessions as having been unfairly obtained. Finally, at the outset of the present appeal, Iain Murray lodged yet a further ground to the effect that the trial judge should have directed the jury that a verdict of culpable homicide was open to them.
 When Brian Wilson was interviewed following his approach to the Commission, he set out his position in relation to the charge. He denied committing the murder or seeing Alison Murray at the locus on the evening of her death. He maintained that he was out for a walk with Iain Murray when the murder was committed and that this account of his activities was in line with his defence and with what he told the police before he was interviewed on 15 June 1986. He accepted that he had admitted to the police that he committed the murder but said that his admissions were false and were made only because of the pressure of the situation. Iain Murray gave a similar statement to the Commission. Thereafter, in the course of their investigation the Commission obtained and studied a large variety of documents including the charge to the jury, the reports by the trial judge in relation to the appeals against conviction, the opinion of the appeal court in relation to those appeals, and transcripts of the evidence of Constable McIvor, Detective Constable Hutchinson, Detective Sergeant McKinnon, Detective Constable Watterson, Detective Sergeant Weir, John Clark, Detective Chief Inspector Tennent, Detective Constable McCrossan, Detective Inspector McKay and Detective Inspector Paul. The transcripts of evidence examined by the Commission are the only surviving verbatim records of the evidence, and all other notes of evidence appear to be destroyed. The Commission also had access to newspaper reports of the trial in the Glasgow Herald and other newspapers, defence precognitions, Crown statements, defence papers, productions and various reports by psychiatrists and psychologists. None of those actively engaged in the trial retained any notes of the case, although a transcript of Iain Murray's evidence at the trial was prepared from the trial judge's handwritten notes. All of this information was made available to Professor Gudjonsson, who provided reports in respect of each of the appellants. Thereafter the Commission interviewed various witnesses including senior and junior counsel for Iain Murray, his solicitor at the outset of proceedings and his solicitor at the trial, and Brian Wilson's senior counsel and solicitor. The Commission then again interviewed the two appellants and obtained supplementary reports from Professor Gudjonsson on each of them. The additional evidence available in the present appeal therefore for Brian Wilson was Professor Gudjonsson's original report for the Commission and his supplementary report. In respect of Iain Murray, the additional evidence was Professor Gudjosson's original report for the Commission, his supplementary report, and two letters dated 6 and 14 March 2004 submitted in respect of further inquiries by the Commission.
Professor Gudjonsson's reports on Brian Wilson
 In instructing Professor Gudjonsson to conduct a psychological examination and prepare a report on Brian Wilson with regard to the reliability of his confessions to the police, in addition to what has been described earlier, various psychiatric, psychological, social work, prison and parole papers which had been obtained by the Commission during their investigation were also provided. In conducting his assessment, Professor Gudjonsson made use of the results of certain tests which had been used by other psychologists carrying out earlier assessments. In particular, Brian Wilson was assessed psychologically in February 1999 by Ms Erica Robb. Three psychological tests were administered. The first was the Wechsler Adult Intelligence Scale/Revised [WAIS-R]. This is an established test to which no objection was taken, or adverse comment offered, in the present appeal. This produced a result of an average IQ of 74, which classified his intelligence as borderline. Secondly, he was subjected to the Gudjonsson Suggestibility Scale tests. These tests (abbreviated to GSS1 or GSS2) employ a narrative paragraph, describing a fictitious robbery, which is read out to the subject, who is then asked to repeat all that can be recalled about the story, immediately, and then again after a delay of about 50 minutes. The subject is then asked 20 specific questions, 15 of which are said to be subtly misleading. After answering the 20 questions, the subject is told that there are a number of errors in the replies (even if this is not the case), and the questions are repeated, and the subject is asked to be more accurate than before. Any change in the answers from the previous trial is known as "Shift" which indicates how the subject responds to interrogative pressure. The extent to which the subject gives in to misleading questions (which can also be measured) is noted as Yield 1. Yield 1 and Shift combine to make up Total Suggestibility. Another concept, Yield 2, refers to the number of leading questions which the subject yields to after the negative feedback has been delivered. In other words, Yield 2 represents the number of suggestions accepted after interrogative pressure, and this can be factored into the overall conclusions drawn from the test. Verbal memory and confabulation (the tendency to fill gaps in one's memory by producing imagined material) can also be measured. GSS2 is a developed form of GSS1. In Brian Wilson's case some of the results from the Suggestibility Scale tests were low and some moderately elevated, but all fell within normal limits. The scores suggest that he gave in rather readily to leading questions, but that he coped reasonably well with interrogative pressure.
 The third test carried out by Erica Robb was the Gudjonsson Compliance Scale (GCS-D), which measures the extent to which an individual is motivated to please others and to avoid conflict and confrontation. This test consists of 20 statements which have to be answered as true or false, and is designed to indicate whether two conditions are present. The first is an uneasiness and fear of people in authority, and the second a desire to avoid conflict and confrontation, and an eagerness to please. Examples of the kind of statements which have to be answered are "I give in easily to people when I am pressured", "I try to please others", "I tend to give in to people who insist that they are right," and "I tend to become easily alarmed and frightened when I am in the company of people in authority." Again, the first appellant fell within the average range for persons in the general population.
 When Professor Gudjonsson himself came to assess Brian Wilson in 2001, he again carried out the Gudjonsson Suggestibility Scale and the Gudjonsson Compliance Scale tests and obtained roughly comparable results. On the suggestibility scale Mr Wilson's confabulation scores were highly elevated. All the suggestibility scores fell within normal limits, although the Yield 1 and Yield 2 scores were also highly elevated, suggesting that Mr Wilson gave in readily to leading questions. In the Compliance Scale test Mr Wilson scored well within normal limits. Professor Gudjonsson also carried out an acquiescence test which measures a person's tendency to answer statements in the affirmative irrespective of content. Brian Wilson's score in respect of this test fell well outside normal limits. Finally in the Eysenck personality questionnaire (EPQ-R) and the Gough Socialisation Scale, the results were well within normal limits.
 In the Culture Free Self Esteem Inventory (SEI), Mr Wilson was found to have satisfactory self esteem across all of the different domains, general, social and personal. Finally, Professor Gudjonsson applied the Gudjonsson Confession Questionnaire - revised (GCQ-R), which contains 52 questions measuring the reasons offenders have given for having confessed to crimes they have committed and which, according to Professor Gudjonsson can also be used to measure why suspects confess falsely to crime. The results, according to Professor Gudjonsson, suggested:
"that Mr Wilson had a poor understanding of his legal rights during the police interview on 15 June 1986 and his resistance was broken down by a severe interrogative pressure. The pattern of scores is consistent with a coerced heightened compliant type of false confessions."
 The conclusions of Professor Gudjonsson's original report to the Commission in relation to Brian Wilson were as follows:-
"1. I found no evidence of mental illness; nor is there any history of mental illness, personality disorder, or established learning disability.
2. The intellectual assessment conducted by Ms Robb in February 1999 reveals a significant intellectual impairment. The Full Scale I.Q. score of 73 falls in the bottom 4 percent of the general population. His verbal skills are particularly weak.
3. On the GSS2, (Gudjonsson Susceptibility Scale 2), Mr Wilson's memory for recalling and retaining verbal material falls in the borderline range for persons in the general population (between 5th and 10th percentile rank) [the fifth and tenth lowest percentiles in the general population] and this is consistent with his Full Scale I.Q. score of 73. During the present assessment, and to a certain extent during the previous assessment with Ms Robb, Mr Wilson was prone to confabulation in memory.
4. Mr Wilson's suggestibility and compliance scores fall within normal limits, although his suggestibility scores during the previous and present assessment were moderately elevated, indicating that he gives in rather readily to leading questions. When Mr Wilson was asked to complete the compliance scale in relation to what he was like prior to his arrest in 1986 his score fell well outside normal limits, indicating an abnormally compliant individual. This suggests that he has changed markedly in his personality since his police interviews in 1986.
5. It seems from the prison records, and from what Mr Wilson told me, that he matured greatly whilst he was in prison, and he is now more able to stand up for himself. Therefore, his current suggestibility and compliance scores may not properly identify the extent of his psychological vulnerabilities when interviewed by the police in 1986 ... Certainly, the early prison records showed an immature person of a timid temperament who would probably not have coped well with pressures of interrogations and confinement.
6. Mr Wilson's very high acquiescence score suggests that he has an abnormal tendency to answer in the affirmative and to contradict himself when in doubt. It suggests that Mr Wilson has problems with understanding questions and statements of moderate complexity and as a result tends to contradict himself. This phenomenon is most commonly found in persons with learning disability ... and is in part undoubtedly related to his limited verbal abilities. It seems from the various documents that I have read in this case that Mr Wilson's limited intellectual abilities had not previously been entirely recognized. Importantly, the officers who interviewed Mr Wilson in 1986 were probably not fully aware of his limited intellectual abilities.
7. The results from the EPQ-R, the Gough Socialisation Scale, and the Culture Free Self Esteem Inventory all fall within normal limits. I found no evidence of personality disorder from the present assessment or from the prison records and reports.
8. At the time of the interrogation in 1986 Mr Wilson was psychologically vulnerable. He was undoubtedly an immature and timid youth of borderline intelligence. He was clearly interviewed over a period of several hours without independent support, it is apparent that he was placed under considerable pressure to confess, and my view is that no weight should be placed on the apparent special knowledge allegedly revealed by Mr Wilson during his interrogation. It is possible that salient case information was being communicated to him during the interview, as he claims, and I am extremely concerned about the ways in which there were apparently telephone conversations on the afternoon on the 15th June between the officers at the two police stations where the two suspects were interrogated. Under such circumstances the risk of contamination is great. The inconsistencies and discrepancies between the accounts given by Mr Wilson and Mr Murray, and the important contradictions with the medical evidence are also of concern. Mr Wilson alleges that during the police interview there were up to six officers in the room with him. If this is the case then this is potentially oppressive for a young, intellectually limited, and immature person.
9. The alleged confession Mr Wilson made to his mother and to Governor Mitchell in 1990 should not be used as credible evidence to corroborate his confession to the police. It is highly probable that on those two occasions Mr Wilson, a person of limited intelligence, was merely giving into pressure he was not able to cope with...
10. Having carefully considered this case, I have great concern about the reliability of the confession Mr Wilson made to the police on 15th June 1986. I consider the confession to be unreliable. The case has the hallmarks of a coerced-compliant type of a false confession.
11. I think it may be worth interviewing the officers in the case to establish how many were present during the interview with Mr Wilson, their recollections of the interviews, and the nature of the telephone conversations that apparently took place between the officers at the two police stations at the time of the interviews of the two men."
 Upon receipt of Professor Gudjonsson's first report, the Commission carried out further investigations. However, it did not consider it necessary to interview any of the police officers involved in the interview with the first appellant, as suggested by Professor Gudjonsson in paragraph 11 of his first report. We are surprised that the Commission should see fit to interview one side of this dispute and not the other. The Commission also examined the admission made by the first appellant to his parents Robert and Jessie Wilson on 15 June 1986 at Clydebank Police Station, referred to earlier. The Commission considered this admission to be linked so closely with the admissions already made by the first appellant on 15 June 1986 that it would not alter the view reached by the Commission in relation to this case. No further reason is given for this conclusion. Also, the Commission considered the comment made by the first appellant to the prison governor George Mitchell in 1990 when being interviewed for the purpose of parole. This is referred to earlier in this opinion, and indicates that the first appellant knew about the circumstances of the murder and in effect was incriminating his former co-accused. The Commission did not consider this comment to be of significance, for the reasons indicated by Professor Gudjonsson.
 A further issue which the Commission looked at was concerned with the terms of the report dated 16 June 1986 by Doctor Gourlay, the police surgeon, of his examination of Brian Wilson on that date at Clydebank Police Office. The police surgeon's report concluded that the appearance of the first appellant's anus provided positive proof of current homosexual activity. It will be recalled that one of the allegations put to the appellants by the police in the course of interview was that they had been engaged in homosexual practices. The Commission also considered a medical report dated 19 September 1986 on Brian Wilson by Doctor McLay, who found no abnormal features and no signs suggestive of the habitual practice of sodomy. Doctor McLay was not however able to say that there were no signs of homosexual activity when the police surgeon examined the first appellant. The first appellant's position during interview with the Commission's investigating officer was that he denied that he had ever had any homosexual experience before his arrest on 15 June 1986. He had denied allegations that he was homosexual during the course of the police interview, although eventually he agreed that he was. The Commission then obtained a report from Professor Anthony Busuttil to provide an opinion on the validity of Doctor Gourlay's findings. Professor Busuttil reported that Doctor Gourlay's conclusions, in the absence of any other medical history, could be the findings of recent sodomy. However, he also reported that certain conditions could give rise to positive medical findings which may mimic closely those found after anal sexual penetration. These matters were put again to Doctor Gourlay who concluded, having reviewed his findings and the reports of Doctor McLay and Professor Busuttil, that he remained of the view that the likeliest explanation for the findings of his examination of the first appellant was recent anal penetration. In these circumstances the Commission found it could not exclude the possibility that there might have been a cause other than anal penetration for the physical features described by Doctor Gourlay. We find the Commission's conclusion on this matter extremely surprising. No attempt appears to have been made to explore either generally or specifically in relation to the first appellant whether the alternative explanations suggested by Professor Busuttil could possibly have applied to him. It is therefore difficult to see why the Commission was in a position to ignore Doctor Gourlay's findings, which could be said to provide clear and cogent corroboration of one aspect of the police version of the interview with Brian Wilson, but which Brian Wilson denied, and to accept the possibility an alternative explanation based on unsubstantial speculation. Our concern is that what appears to be a clear piece of evidence, which in the context of the case we regard as particularly significant, has been unaccountably ignored by both the Commission and Professor Gudjonsson. Had it been accepted for what it is worth, it might have had a material bearing on the decision to refer the case to this court.
 However, to return to the Commission's investigation, the Commission was anxious to get a supplementary opinion of Professor Gudjonsson because of the marked difference between the first appellant's description of the police interview and that contained in the Crown evidence. Brian Wilson maintained that he was, in part, bullied by threats and intimidation from the police into admitting the murder of Alison Murray. In particular, he maintained that pressure was put on him by the allegation that he was a homosexual, that he was threatened with some form of violence, and that at one point he was grabbed and thrown to the floor.
Professor Gudjonsson's supplementary report was in the following terms:
"1. There is nothing in your letter to me dated 16 December 2003 that undermines the conclusions that I reached in my original psychological report. I have seen nothing that satisfies me that Mr Wilson's version of events could not have been true. Furthermore, it is the subjective experience of the detainees which is more important at the time than the objective reality of the situation influencing his behaviour (i.e. his perceptions and beliefs about what is happening.)
2. At the time of Mr Wilson's trial in 1986 there was absence of knowledge about psychological vulnerabilities and their potential impact on the reliability of confession evidence. The importance of psychological vulnerabilities in disputed confession cases has only been fully recognised in recent years...
3. In the great majority of cases of miscarriage of justice there is a significant discrepancy between the evidence of the Crown and that of the defence and the jury invariably believed the police evidence and convicted the defendant. I have identified a number of these cases in my recent book... The fact that Mr Wilson's account of the police interview differs in several respects from that of the police officers in the case is typical in these kinds of cases. I do not think that the discrepancy undermines Mr Wilson's credibility as a witness any more than that of the police.
4. We do not know exactly what was said and done in the interview with Mr Wilson. Unfortunately, there was not audio, video or contemporaneous recording of the interview.
5. I am in no doubt that at the time of the interview on 15th June 1986 Mr Wilson was psychologically vulnerable and he would have been susceptible to giving an unreliable confession if pressured by the police. We do not know from an independent source how much pressure he was placed under, or the type of pressure. Importantly, we know that Mr Wilson initially gave a denial and his denials were undoubtedly challenged by the police, which included allegations over his sexuality. Something must have broken down Mr Wilson's resistance and it would not have been the confrontation of credible forensic or identification evidence against him. So why did he break down? The most likely explanation is that he could not cope with the pressure of the interview due to the robust or intimidating nature of the interview..."
Professor Gudjonsson's original report for the Commission on Iain Murray
 A similar procedure was adopted by the Commission in respect of Iain Murray. As in the case of Brian Wilson various psychiatric, psychological, social work, prison, parole papers and police statements were passed to Professor Gudjonsson with other various case related papers. Professor Gudjonsson embarked upon essentially the same process with Iain Murray as he had done with the first appellant. First of all, Professor Gudjonsson noted that Iain Murray was assessed psychologically in 1998 by Gerry Rooney, a clinical psychologist. During those assessments four psychological tests were administered. Unfortunately Mr Rooney failed to include in his report the scores with regard to three of the tests, namely GSS1 and 2 and GCS. In respect of the Weschsler Adult Intelligence Scale - revised (WAIS-R), the second appellant's IQ was found to be average, although there was a significant discrepancy between his verbal response and performance which may have been due to some organic dysfunction. In terms of GSS1 and GSS2, Mr Rooney reported that Mr Murray's immediate and delayed recall was poor in both tests and that during the first assessment his memory score fell at the bottom 25% of the general population. During the second session this had fallen to the bottom 10%, and a significant number of confabulations were noted in his verbal recall. With regard to suggestibility, the most notable finding was an abnormally high Shift (95th percentile rank). However, it was also recorded in the report of Morag Slesser, another psychologist, dated 8 February 1999, that the second appellant had been assessed on the GSS1 as having scored low on suggestibility. In terms of GCS-2, the second appellant's performance was described as highly compliant and in the top 5% of the general population.
 Professor Gudjonsson carried out similar tests in 2003. In respect of GSS2, the second appellant's immediate and delayed recall scores fell well outside the normal range and were considerably worse than expected from his overall average intelligence. However, all the suggestibility scores fell well within normal limits. In respect of GCS-2, the second appellant demonstrated a very high degree of motivation to please others and to avoid conflict and confrontation with people, and his score fell well outside normal limits. It appears that the second appellant told Professor Gudjonsson at the time that if he had completed the scale in 1986 the score would have been very similar.
 In terms of the standard acquiescence tests, the Eysenck Personality Questionnaire and the Gough Socialisation Scale, Iain Murray fell well within normal limits as he also did in two other tests. In terms of the Gudjonsson Confession Questionnaire - revised (GCQ-R), the results suggested to Professor Gudjonsson that Iain Murray had a poor understanding of his legal rights during the police interview on 15 June 1986 and that his resistance was broken down by a combination of marked interrogative pressure and some internal pressure to confess. The pattern of scores was considered by Professor Gudjonsson consistent with the coerced-compliant type of a false confession. No other useful findings were reached. Professor Gudjonsson's conclusions were as follows:
"1. I found no evidence of mental illness, personality disorder, or learning disability.
2. The intellectual assessment conducted by Mr Rooney in 1998 showed average intellectual abilities (Full Scale IQ score of 92), but there was a 31point discrepancy between his verbal (81) and non-verbal (113) intellectual abilities. Such a large discrepancy is very unusual and may indicate some organic dysfunction.
3. On the GSS2, Mr Murray's memory for recalling and retaining verbal material fell well outside normal limits. His poor verbal memory was also noted during previous testing. The reason for his poor verbal memory is not clear. It could be due to attentional problems, emotional/anxiety problems, or organic factors.
4. Mr Murray's suggestibility scores fell within normal limits during the present assessment using the GSS2. During previous assessments by Mr Rooney and a prison psychologist (Morag Slesser) the GSS1 and GSS2 were apparently administered. It appears that prior to the present assessment Mr Murray may have had four previous assessments with regard to his suggestibility, using the GSS1 and GSS2 (Mr Rooney and Ms Slesser both appear to have administered the GSS1 and the GSS2). When assessed by Mr Rooney Mr Murray apparently obtained abnormally high Shift scores, indicating that he did not cope well with interrogative pressure. During the assessment with Ms Slesser, the scores were within normal limits, as they were during the present assessment. It is possible that the low suggestibility scores during the present assessment, and during the assessment with Ms Slesser, may have been reduced due to familiarity with the test.
5. Similar to the findings of Mr Rooney, Mr Murray obtained an abnormally high score in the Gudjonsson Compliance Scale, indicating that he still has a strong tendency to avoid conflict and confrontation with people and authority and he is very eager to please. This personality characteristic is most consistently related to the coerced-compliant type of false confession.
6. The results from the EPQ-R, the Gough Socialisation Scale and the Culture of Free Self Esteem Inventory fall within normal limits. There is no evidence of personality disorder from the present assessment or from the prison records and reports. However, the results from the MMP1-2 and the interview with me suggest a man who is prone to mood and emotional disturbance. This is probably the consequence of the extensive sexual abuse he suffered in childhood from his father. Mr Murray is still deeply disturbed by these past experiences and at the time of the police interviews he would have been suffering even more (i.e. not having been able to talk to anybody about the abuse, feeling he was all on his own with his problem).
7. I am in no doubt that at the time of the police interview in 1986 Mr Murray was a psychologically vulnerable individual. He was probably depressed at the time due to the sexual abuse he experienced in childhood and adolescence, had poor self-esteem, lacked self-confidence, was of a compliant temperament, and would have been very sensitive to allegations of homosexual activity. He was interviewed over a period of several hours without independent support, he was undoubtedly placed under considerable pressure to confess, and may not have fully understood his legal rights. No evidential weight should be placed on the apparent special knowledge allegedly revealed by Mr Murray during his interrogation. It is highly probable that salient case information was being communicated to him and I am extremely concerned about the ways in which there were apparent telephone conversations on the afternoon of 15th June between the officers where the two suspects were interrogated. Under such circumstances the risk of contamination is great. The inconsistencies and discrepancies between the accounts given by Mr Murray and Mr Wilson, and the important contradictions with the medical evidence are also a concern.
8. The fact that Mr Murray subsequently reiterated his confession to his father, in the presence of police officers, should not be used as credible evidence to corroborate his confession to the police. ...
9. Having carefully considered this case I have great concern about the reliability of the confession Mr Murray made to the police on 15th June 1986. I consider the confession to be unreliable. It has the hallmarks of the coerced-compliant type of false confession."
 Upon receipt of Professor Gudjonsson's report on Iain Murray, the Commission carried out further investigations. In particular the Commission considered the terms of the transcript of his judicial examination on 23 June 1986, the transcript of D.C. Hutchinson's evidence, and information from his legal representatives following his arrest. As indicated earlier, at the judicial examination, Iain Murray accepted that he had admitted to his father that he had been responsible for the murder. Subsequently, the evidence of D.C. Hutchison at the trial to the effect that Iain Murray had made an admission to his father was challenged in cross-examination, on the basis of the second appellant's instructions, that he had not made such an admission. The Commission also concluded that Iain Murray gave evidence at his trial that he had not made any admissions to his father, and that such evidence was untrue. In that regard, the Commission noted that at a meeting with its legal officer, on 9 September 2003, Iain Murray accepted that he had made the admissions in question to his father. He also maintained that that had been his position at the trial.
 Finally in this respect, the Commission interviewed Gerald Hanretty Q.C., who was Iain Murray's solicitor during initial court proceedings. Mr Hanretty's statement was that the second appellant accepted that he had killed Alison Murray and that he was "putting his hands up to the killing." In these circumstances the Commission instructed Professor Gudjonsson to prepare a supplementary report. The supplementary report is in the following terms:-
"It is evident that two days after confessing to the police on 15th June 1986 Mr Murray confessed to the murder of his half-sister Alison Murray to his father in the presence of a police officer (Detective Constable Edward Hutchinson). When judicially examined on 23rd June 1986, Mr Murray fully admitted that he had made an admission to his father. However, it seems from the available evidence that when the case went to trial in October 1986, Mr Murray denied having made the admission to his father. When I interviewed Mr Murray on 3rd November 2001, and when more recently interviewed by the SCCRC (9th September 2003), he fully admitted having made the admission to his father.
When interviewed on 9th September 2003 by the SCCRC, Mr Murray said that he 'vaguely remembered giving evidence at his trial about the discussion with his father.' The applicant stated that he would have confirmed at his trial that the discussion did take place and that he had said what was referred to in the transcript of the judicial examination. However, the applicant stated that he could not remember having ever discussed this aspect of the evidence with his solicitor or counsel."
On the face of it, the most logical conclusion to be drawn from this sequence of events is that Mr Murray lied to his legal team at trial with regard to his confession to his father, and possibly also lied in his evidence in court (i.e. misled the court and committed perjury). However, it is possible that Mr Murray was confused at the time and did not wilfully perjure himself. His recent recollection to the SCCRC that he had told the Court the truth as given during the judicial examination on 17 June 1986, which seems to be wrong, may represent a genuine belief. During my own examination of Mr Murray, his verbal memory scores fell well outside normal limits. His exceptionally poor memory had also been found in 1998 when Mr Gerry Rooney tested Mr Murray. In addition, the 32 point discrepancy between Mr Murray's verbal and non-verbal intellectual skills, in favour of the latter, may indicate some underlying organic dysfunction.
If Mr Murray did deliberately mislead his legal team and the Court then this, in a general sense, undermines his credibility as a witness, because the question that may be asked is what else he may be lying about with regard to his case. However, I would advise that the apparent "lies" should be treated with caution for the following reasons. Firstly, we do not know exactly what Mr Murray told his lawyers or the Court in 1986 about the admission to his father. Secondly, we do not know much about the circumstances surrounding the alleged denial of the admission to the father and the motivation behind that action. Thirdly, lying to one's legal team or in Court does not automatically imply that the person is guilty of the offence. Innocent people may also be motivated to deceive the Court in order to strengthen their case. Fourthly, Mr Murray apparently did not attempt to deceive me or the SCCRC about his admission to his father.
It seems from what Mr Hanretty told the SCCRC when they interviewed him recently that Mr Murray's initial instructions were that he was admitting the offence and intended to plead guilty. This changed within three days and the case was taken over by Mr Lanigan. Mr Hanretty's recollection of the case is vague, but there seems on the face of it to be no serious reason to doubt the reliability of his recollection with regard to Mr Murray's instructions to plead guilty. Indeed, Mr Hanretty's recollection is consistent with that given to me by Mr Murray when I interviewed him on 16 July 2001 (see my original Psychological Report, page 14).
'After the confession Mr Murray considered pleading guilty to the murder charge'.
'I remember being offered a solicitor and at the time I thought I would plead guilty and get it over and done with. I didn't know what prison was like then so I wasn't afraid of it. I wanted to plead guilty and I didn't want to put my family through the court. I wasn't terrified of prison. After a few days I settled in. I was slashed initially and then I was put on to suicide watch.'
'I questioned Mr Murray further about this and asked him if he would have pleaded guilty to something he had not done. He replied "It doesn't matter. It would come to the stage that 90% of the people would still think I did it, even if I was acquitted. I didn't want to have to go home and face my family.'
Mr Murray reiterated his confession to his father, in the presence of the police officers two days after having made the confession to the police. According to the judicial examination on 23rd June 1986, Mr Murray is reported as confessing to his father after his father stated:
"If you done it you'll plead guilty to it, you're no bringing the family through the courts, your mother cannae stand it".
Mr Murray's explanation for having made the confession to his father was "I was scared by the police still and the police were in the room, that's why I carried on saying that I was guilty."
There are two points I wish to make with regard to the confession Mr Murray made to his father on 17th June 1986. Firstly, his explanation at the judicial examination is credible. Similar circumstances have been reported in the literature. ... Secondly, Mr Murray had been extensively sexually abused in childhood by his father. Being confronted by his father and in the way he was could easily have influenced his decision making to reiterate his confession to the police and to his father. At the time Mr Murray was undoubtedly psychologically very vulnerable to give in to perceived pressure.
1. Two days after confessing to the police on 15th June 1986, Mr Murray confessed to the murder of his half-sister Alison Murray to his father in the presence of a police officer (Detective Constable Edward Hutchinson). It seems that at trial Mr Murray denied having made the confession to his father. One way of construing this is that Mr Murray was attempting to lie to his legal team and the Court. However, I have argued that this interpretation should be viewed with caution. Even if Mr Murray did mislead the Court at the time of his trial I do not believe that this undermines the conclusions I reached in my psychological report dated 3rd November 2001. At the time of his interrogation Mr Murray was a psychologically vulnerable individual and would have had difficulties coping with confrontations following his initial admission of having been involved in the murder of Alison Murray.
2. The confession that Mr Murray made to his father two days after making the confession to the police should be treated with the greatest of caution. It should not be viewed independently of the confession he made to the police."
 Following receipt of this supplementary report, the Commission asked Professor Gudjonsson to clarify whether the psychological vulnerabilities of Iain Murray may be less significant if and when it is accepted that he admitted responsibility for the killing of Alison Murray to his solicitor. Professor Gudjonsson replied by letter dated 6 March 2004 in the following terms:
"... As a general rule, suspects who confess to the police due to external pressure or coercion (e.g. threats, inducements, intimidating interviewing, psychological manipulation) do tend to retract their confession once the pressure is over. This usually happens when they see their solicitor for the first time, but there are exceptions to this general rule. In the case of Mr Murray, he appears to have confessed to the murder to his first solicitor, Mr Hanretty, and initially intended to plead guilty. I discussed all this in my Supplementary Psychological Report, dated 15th February 2004, as well as in my original Psychological Report.
The reasons why a suspect maintains a confession are often different to the reasons why the confession was made in the first place. As far as Mr Murray is concerned, the explanations he gave me as to why he had initially wanted to plead guilty to the murder (e.g. he was not frightened of prison, did not want to put the family through the court, thought people would still think he was guilty even if he was not, and did not want to go home and face his family) are at least plausible in view of Mr Murray's likely psychological problems at the time and his poor self-esteem. Prior to his police interview on suspicion of murder, Mr Murray had been subjected to childhood sexual abuse by his father and he undoubtedly did have problems relating to his sexuality and selfesteem. Two days after making the confession to the police he confessed to his father in the presence of the police. His father had told him to plead guilty, if he had committed the offence. The father's comments to his son, in the context of a history of childhood sexual abuse, do complicate the picture. Mr Murray's psychological vulnerabilities may have impacted not only on his initially making a confession, but also on his decision to maintain it, to plead guilty and the confession to his first solicitor. The alternative, of course, is that Mr Murray committed the offence and wanted to plead guilty to it, but for some reason changed his mind (e.g. after having had time to think about the likely consequences of a conviction and learning about the absence of evidence against him).
The fact that Mr Murray confessed to his first solicitor and had initially wanted to plead guilty to the murder, does weaken his claims that he had made a false confession to the police, although looking at the case as a whole, I still have reservations about the reliability of the confession he made to the police, his father and his solicitor."
 Finally, the Commission asked Professor Gudjonsson to clarify some other matters which are not relevant to the present appeal. In addition they asked Professor Gudjonsson to quantify or describe how much weaker the second appellant's claim that he had made a false confession became having regard to his apparent failure to retract the confession. Professor Gudjonsson's response in his letter of 14 March 2004 is as follows:
"It is not realistic to quantify this as you request and I have addressed it previously as fully as I could, although I would not go as far as saying that it substantially weakened his claim of innocence. The issue in this case is not whether or not Mr Murray made a false confession to the police; the emphasis should be on the reliability of the confession (i.e. under the circumstances it is safe to rely on it). The other way of expressing it is that if Mr Murray had retracted the confession to his solicitor at the earliest opportunity then this would have to a certain extent strengthened his claim of unreliability of the confessions. His not retracting the confession at the earliest opportunity requires an explanation and he has given one, which seems plausible".
Criticism of Professor Gudjonsson's methodology
 In response to the evidence submitted by Professor Gudjonsson on the part of the appellants, the Crown led the evidence of two witnesses who commented on the methodology used by Professor Gudjonsson in reaching his conclusions. Doctor Gary Macpherson, a consultant forensic clinical psychologist at the state hospital, Carstairs, disagreed with the conclusions which Professor Gudjonsson drew from the material he had examined. Doctor Macpherson agreed that one of the difficulties in the case about forming a firm view on the fairness or otherwise of the police interviews was the absence of contemporaneous recording. He accepted that the first appellant's low level of intellectual functioning might render him vulnerable in the context of a police interview, and that there was general agreement from a number of psychologists that the second appellant's personality would also have made him vulnerable during a police interview. However, on examining the same material as Professor Gudjonsson, Doctor Macpherson found no compelling evidence to suggest that the confessions of the appellants were unfairly obtained. He noted the history of each appellant's confession. He found no evidence in the material before him or in the accounts supplied by the appellants to indicate that salient material was "suggested" to them. He found no evidence to suggest either of the men falsely began to believe that he had committed the murder. He noted that, in the appeal court hearing following the original trial, it was not suggested that there was any unfairness in the conduct of the police which should have rendered those admissions objectionable.
 Further, Doctor Macpherson noted that, on the issue of interrogative suggestibility, neither appellant was regarded as suggestible in the terms of the Gudjonsson Suggestibility Scale. In relation to the repeated confessions, Doctor Macpherson noted that Brian Wilson repeated his confession in front of his parents, and that Iain Murray repeated his confession to independent police officers not only in the absence of any pressure, but following strong and unambiguous advice from the duty solicitor not to do so. Subsequently he told his instructed solicitor that he was responsible for the murder. Doctor Macpherson found this most unusual, and he also considered that the repeated failure on the part of the second appellant to retract his confession, and indeed to reiterate it, was highly significant. On the occasions of these repeated confessions there appeared to have been no direct pressure placed on the appellants, and in terms of the relevant professional literature and Professor Macpherson's own experience, that was when persons who had falsely confessed to the police generally retracted their confessions rather than repeating them. He therefore had considerable doubts on the conclusions reached by Professor Gudjonsson to the effect that the appellants' vulnerability led to their confessions being unreliable. Doctor Macpherson also noted that Brian Wilson made an incriminating statement during his prison sentence, again in the absence of any pressure. He was unable to reconcile Iain Murray's behaviour, in informing his solicitor that he wished to plead guilty to murder, and providing a voluntary statement confessing to the murder after he had been warned in the strongest terms against doing so, with his claims of having made a false confession to the police.
 Further, in respect of Iain Murray, Doctor Macpherson noted that his earlier tests suggested that he was of average intelligence, and that the results of the Gudjonsson Susceptibility Scale fell within normal limits. The score on the Gudjonsson Compliance Scale (confirmed by an earlier test) was abnormally high. Doctor Macpherson commented that the other tests used by Professor Gudjonsson are not normally applied in forensic clinical psychology practice. In the present case, as both appellants scored within normal limits in the Suggestibility Scale, the principal psychometric evidence to support "the coerced-compliant false confession", certainly in respect of Iain Murray, rested on the results of the Gudjonsson Compliance Scale test. In Doctor Macpherson's view this was a highly transparent and easily fakeable measure that should not be relied on, and its usefulness was undermined by the fact that all of the information on which the test was based came from the subject. The test consists of twenty questions which the subject has to answer, designed to incorporate two principal characteristics, eagerness to please and avoidance of conflict. In expressing his reservations about this measure, Doctor Macpherson noted that it was open to manipulation, and to inaccuracy because of a lack of insight on the part of the subject, and suggested that some form of corroboration would be desirable. Professor Gudjonsson said that he had observed the appellants during the test and that those observations tended to confirm the answers which he received. He also referred briefly to some contemporaneous references in the records. However, it would appear, particularly from the subsequent evidence of Professor David Cooke, which on this matter we accepted, that far more in the way of direct corroborative information would have been required to provide the results of the Compliance test with any real value. It is right to say that Professor Gudjonsson acknowledged much of the critical commentary himself, both in his evidence and in his books, although the impact of such criticism on his own conclusions in this case remained unclear. While Doctor Macpherson accepted that in terms of the test it could be said that Iain Murray was abnormally compliant, he suggested that his failure to retract the confessions was inconsistent with the claim that a false confession had been induced by a subject with a compliant personality.
 In respect of the first appellant, Brian Wilson, Professor Gudjonsson's opinion was that his subsequent confessions to his parents following his arrest, and his admission of intimate knowledge of the facts of the murder to Governor Mitchell some years later in prison, should be ignored on the basis that the first appellant was a person of limited intelligence, and was merely giving in to pressure he was not able to cope with. Doctor Macpherson said that he was unable to share his view as he could not identify where the pressure could have come from on each of these occasions. He also noted that in both the Gudjonsson Susceptibility Scale and the Gudjonsson Compliance Scale, the first appellant fell within normal limits, and that these issues are therefore not significant in his case. Doctor Macpherson then seriously questioned the merit of inviting a person convicted of murder, and who is pursuing an appeal, to participate in a measure as transparent as the Gudjonsson Compliance Scale some 15 years after the incident, as it is in such circumstances dangerous to assume honest reporting by the subject, particularly in a forensic setting. In conclusion, Doctor Macpherson noted unusual and unsatisfactory aspects of the police interviews but concluded that the voluntary and self incriminating statements provided by the appellants to others were not, on the evidence, obtained or given following repeated questioning or pressure.
 The Crown also led evidence from Professor David Cooke, who is Professor of Forensic Clinical Psychology at Glasgow Caledonian University and who has a formidable list of qualifications, positions and publications. He was asked specifically to review the papers provided in order to prepare an opinion on the validity of the reports prepared by Professor Gudjonsson in relation to the technical aspects of his analysis and, in particular, to comment on the reliability of the Gudjonsson Scales in respect of specific confession evidence, the fact that both Scales and in particular the Compliance Scale are based on self-reporting, whether it would make a difference that the tests were carried out so long after the alleged confessions, and whether it was appropriate to use a test based on how the subject considers he would have completed it at the time he made the confession. He was therefore not concerned to provide an overarching evaluation of whether there was psychological evidence in support of the contention that the confessions may be unsafe.
 Having considered the material, Professor Cooke in his report offered a detailed statistical analysis of both the Gudjonsson Susceptibility Scale and the Gudjonsson Compliance Scale scores, which suggested that the results obtained by these tests might lack precision, and that it was therefore difficult to determine accurately in any one case whether an individual could be regarded as falling outwith the normal range, and could be described, for example, as abnormally suggestible or compliant. Regrettably, in our view, the Advocate depute, for reasons which remain obscure, declined to pursue this part of his report with Professor Cooke, which might have shed light on the impact of the need for measurement precision in considering the results produced by Professor Gudjonsson's methods. However, we are able to look at Professor Cooke's criticism of the use of the Compliance Scale in the present case. Firstly, Professor Cooke repeated Doctor Macpherson's criticism that the test is essentially transparent, although he did so in more detail. For Professor Cooke, the difficulty was that the questions asked in the GCS1 (helpfully produced at the end of Doctor Macpherson's report) are so markedly transparent that someone wishing to appear compliant will know how to answer the questions in order to do so. Professor Cooke stressed the particular limitations of using such a test in a forensic evaluation, where the individual being assessed stands to gain or lose from the outcome of the case which the test is designed to serve. Perhaps more significantly, Professor Cooke doubted that the first appellant Brian Wilson should have been subject to the Compliance Scale test at all, because of his intelligence levels at the material time and at the time of the test. Professor Gudjonsson himself had indicated both in print and in his evidence before this court that these tests are not suitable for persons of low intelligence, as the subject would have difficulties in understanding some of the statements contained in the test. Reliance on self report for persons of average intelligence may produce an accurate account, but the test should not be used for persons of lower intelligence. These factors would appear to rob the test, in the case of the first appellant, of much of its relevance and, it seems to us, must cast substantial doubt on Brian Wilson's true level of compliance.
 Even when the test is used, Professor Cooke gave convincing testimony (as we have noted earlier) that it is necessary to obtain as much confirmation from independent and reliable collateral sources as possible (for example directly from family, friends and workmates) in order to make an effective assessment of the subject's compliance. This was not done in the present case. Professor Gudjonsson suggested that he had obtained such confirmation by his visual observations of the appellants during the test, and had looked at some contemporary records, but in our view, that corroboration was not particularly convincing. A further point made by Professor Cooke was that if the confessions contained knowledge that was special in the sense that it was information known to someone involved in the offence, the conclusions of the test, purporting to show the confessions were unreliable, would be at once invalidated. He further concluded that the interval between the testing of the appellants by Professor Gudjonsson and the original police interviews was such that it was difficult to infer that an assessment of either appellant in 2001 could be said to produce similar conclusions as to what would have been the position in 1986. Professor Cooke considered that it was wholly unsafe to rely on a subject's responses to a test which was completed on the basis of how he believes he would have completed that test some 15 years earlier. Particularly when used retrospectively, GCS2 was an inadequate instrument to measure the construct of compliance and he himself had stopped using it.
 In cross examination Professor Cooke readily accepted that Professor Gudjonsson's scales had been widely used and accepted, but repeated that their use was always subject to analysis and review, and that in his opinion the principal value of these scales was in clinical and research fields. Professor Gudjonsson himself had acknowledged the limitations of his methods. In the case of Brian Wilson, where Professor Gudjonsson had, it would appear, relied primarily on the results of the Compliance Scale tests, Professor Cooke was satisfied that no satisfactory forensic conclusions could be drawn from those results.
 At this point, in view of the significance of Professor Gudjonsson's testimony in this case, we should now consider what we believe to be the proper character of expert evidence, and in particular attempt to describe our understanding of its nature and effect on the conclusions we should draw. In general, of course, opinion evidence is not admissible in our criminal courts; witnesses may only under normal circumstances give evidence about matters within their direct knowledge. The evidence of an expert witness is an exception to this rule. It is not possible to provide an absolute direction as to what constitutes legitimate subject matter for expert opinion. However, two general principles will normally give some guidance. Firstly, the subject matter under discussion must be necessary for the proper resolution of the dispute, and be such that a judge or jury without instruction or advice in the particular area of knowledge or experience would be unable to reach a sound conclusion without the help of a witness who had such specialised knowledge or experience. Secondly, the subject matter in question must be part of a recognised body of science or experience which is suitably acknowledged as being useful and reliable, and properly capable of reaching and justifying the opinions offered, and the witness must demonstrate a sufficiently authoritative understanding of the theory and practice of the subject. The nature and scope of expert opinion evidence cannot at any one point in time be exhaustively defined.
 The effect of expert opinion evidence can perhaps be described with more precision. The role of the expert witness, and his duties and responsibilities, have been subject to much judicial comment. In National Justice Campania Naviera, S.A. v Prudential Assurance Co. Ltd ("The Ikarion Reefer")  2 Lloyds Rep 68, Cresswell J listed a number of such duties and responsibilities, inter alia -
"1. Expert evidence presented to the court should be, and should be seen to be, the independent product of the expert uninfluenced as to the form or content by the exigencies of litigation.
2. An expert witness should provide independent assistance to the court by way of objective unbiased opinion in relation to matters within his expertise.
3. An expert witness should state the facts or assumptions on which his opinion is based. He should not omit to consider material facts which could detract from his concluded opinion.
4. An expert witness should make it clear when a particular question or issue falls outside his expertise."
 To this might be added a requirement that an expert witness should in particular explain why any material relevant to his conclusions is ignored or regarded as unimportant. Although the categories of duty and responsibility described by Cresswell J in the Ikarion Reefer case were concerned with civil matters, these rules are equally applicable to criminal cases.
 In addition, particularly in criminal cases, other duties and responsibilities have been recognised by the courts. For example, the court will expect in a criminal matter that an expert's report must state the facts upon which opinions are based, and if assumptions are made, these must be clearly identified. Reasons must be given for conclusions. Whether instructed for the prosecution or defence, the principal duty of an expert witness is to the court, and this overrides any duty he owes to the party which instructed him. Again, explanations should be given for the basis on which all relevant material is either accepted or rejected.
 It therefore follows that a judge or jury is not bound by the opinion evidence tendered by an expert witness. There are clear principles under which such evidence is admitted. In Davie v Magistrates of Edinburgh 1953 S.C. 34 the Lord President Cooper said (at p40):-
"Expert witnesses, however skilled or eminent can give no more than evidence. They cannot usurp the functions of the jury or the Judge sitting as a jury ... Their duty is to furnish the Judge or jury with the necessary specific scientific criteria for testing the accuracy of their conclusions so as to enable the Judge or jury to form their own independent by the application of these criteria to the facts proved in evidence. The scientific opinion evidence, if intelligible, convincing and tested, becomes a factor (and often an important factor) for consideration along with the whole other evidence in the case, but the decision is for the Judge or jury. In particular the bare ipse dixit of a scientist, however, eminent, upon the issue in controversy, will normally carry little weight, for it cannot be tested by cross-examined nor independently appraised, and the parties have invoked the decision of a judicial tribunal and not an oracular pronouncement by an expert."
Although in modern practice (as in the present case), expert evidence is routinely appraised and cross-examined, the position essentially remains that an expert witness's opinion is only a factor (albeit an important one) in the decision of a judge or jury.
 It is abundantly clear therefore, and has been for many years in our courts, that an expert witness is not in the position to provide the court with a statement of unqualified conclusions about the question of fact on which his opinion bears. If he does so, the effect of his testimony may well be much diminished. In this context, it is perhaps worth noting that an expert witness is in a particularly privileged position in our courts. Prior to the decision, he is the only person permitted to express an opinion. Other witnesses must confine themselves to facts. Further, an expert witness will routinely rely on assumptions, hearsay evidence, his impression of testimony that he has not heard, and reports, statements and other secondary sources of information, all of which might be incompetent in a court of law if presented as factual evidence. It is therefore of the utmost importance that any expert witness carefully describes the source and assesses the worth of all material on which his opinion is based. We refer to the case of Gilmour v H.M Advocate, paras  and . It is a matter of considerable concern therefore to note that, in his reports on the appellants (cited in the case of Brian Wilson at para.  of this opinion, and in the case of Iain Murray at para. ), Professor Gudjonsson states unequivocally that he considers the confessions made by the appellants to the police to be unreliable. That is not a conclusion that an expert witness should draw. His role is to place his opinion before a court or jury in the fashion described above, in order to allow the court or the jury to reach a proper conclusion on the matter. We therefore require to reject Professor Gudjonsson's conclusions as expressed, while continuing to have due regard to his opinions on the vulnerability of both appellants which led to his conclusions.
Nature of additional evidence
 We now turn to say something about the nature of the evidence which has to be considered in cases of this sort, and also the nature of the evidence which appears to have been considered by Professor Gudjonsson and, separately, by the Commission. Firstly, so far as the evidence before the court is concerned, and the way it should be approached, we have found ourselves in some difficulty. In a joint minute of agreement signed by the Advocate depute and counsel for both appellants, it is agreed that "all the evidence elicited in the course of the hearing shall be admissible in respect of both appeals," and also that "all material contained in the appendices to the appeal prepared by the Scottish Criminal Cases Review Commission is available to be considered by the court." In discussion with counsel, it was agreed that in effect these various passages meant that the court was entitled to look at and assess all of the material which was before Professor Gudjonsson and the Commission and to make of it what the court thought appropriate. This is, in our view, unsatisfactory; questions arise at every turn as to the value and strength of almost every individual piece of evidence contained in the papers before us, and which were formerly before the Commission and Professor Gudjonsson. Much of this evidence was not, and could not have been, before the jury, some because it relates to incidents after the trial was over, and some because it could never have been competently led before a jury in the first place. It is difficult to know what weight and value can confidently be placed upon such evidence. In the result, what appears to be expected of the court in this situation is to consider the whole picture presented by all of the information submitted to it, giving to that information such weight and value as appears to be reasonable and realistic in the circumstances, and then come to a view as to whether there has or may have been a miscarriage of justice. This is a frustrating exercise. As an illustration, in a further joint minute of agreement signed by counsel for the second appellant and the Advocate depute, it is said that the affidavits sworn by Iain Murray and dated 4 December 2008 (which was in the middle of the present appeal) were "to be treated as his evidence on the matters contained therein for the purposes of the appeal against conviction." The evidence in the second appellant's affidavit relates to allegations of sexual abuse by his father when he was a child. Presented as an affidavit, it is impossible to judge whether these allegations are true, or more importantly, if they were true, what relevance they might have had, in the appellant's view, to the crucial issues in the appeal. In his reports on the second appellant, Professor Gudjonsson has assumed that these complaints were true, and for reasons which are not entirely clear, could have contributed to the making of a fake confession. Again, the evidence of Gerald Hanretty, now a silk practising at the Scottish Bar but at the material time Iain Murray's solicitor when he was on remand, was, in our view, on the basis of his precognition, a clear statement to the effect that the appellant had admitted to his responsibility for the killing. On the other hand, it appears that Professor Gudjonsson's interpretation of the same statement was far less positive; he speculated that there may be some doubt as to whether the appellant was perhaps simply indicating that he intended to plead guilty, rather than admitting that he had murdered his step-sister. Although the difficulties presented by both these issues, for example, might have been resolved by the proferring of direct evidence from the principal sources (which appear to have been readily available), such testimony was not presented to the court.
 Another example of this sort of difficulty is found in yet a further minute of agreement signed by the Advocate depute and counsel for the second appellant which provides, relating to the evidence in the appeal, that
"All documents considered by Professor Gudjonsson (when giving evidence or otherwise) which contain information relating to Mr Murray's character, intellectual functioning and personality are accurately recorded and contain genuine expressions of view."
For the sake of completeness and avoidance of doubt, we should indicate that in respect of that agreement, we have no difficulty in proceeding on that basis; however, as Lord Prosser pointed out in Dingley v Chief Constable, Strathyclyde Police 1998 S.C 548, 604; "As with judicial or other opinions, what carries weight is the reasoning, not the conclusion." Examples of this sort of difficulty proliferated throughout our consideration of the various adminicles of evidence. However, we fully accept that realistically, if all of the existing and potential sources of information had been led in evidence before the court, the proceedings would have been interminably protracted.
 We met with further difficulties in the way in which the Commission and Professor Gudjohnsson approached some of the evidence. For instance, the Commission reviewed extensively the position of both appellants and that of Professor Gudjonsson, but did not revisit the Crown case or any of the prosecution witnesses. Further, the Commission rejected as insignificant the repeated confessions of the appellants without in our view providing any satisfactory reasons for so doing, and, more significantly, appears, to have paid insufficient attention to the special knowledge of the circumstances of the offence found in the appellant's admissions, particularly by Iain Murray. In coming to terms with some of these issues, Professor Gudjonsson was dismissive of much of the evidence if it did not fit his conclusion that the appellant's confessions were unreliable, and he was prepared to engage in speculation about how certain parts of the evidence came to be before the court. He was for example prepared to suggest that the second appellant when in the interview room at Clydebank Police Station could have accidentally received knowledge of what the first appellant had said as a result of overhearing a telephone conversation received in the incident room, which he supposed might be next door. In reading all the notes of the evidence, it is plain that the incident room was on a different floor in the building. In his report on Iain Murray, he wrote: "It is highly probable that salient information was being communicated to him" while in the police station. There was no evidence to justify this conclusion. This tendency to stray into advocacy causes uncertainty about the true nature of various sources of the information used by Professor Gudjonsson in reaching his conclusions, and emphasises the difficulty of basing opinions on speculative or incompetent evidence. In the circumstances we consider it would be appropriate to regard as less important any part of an expert witness's testimony which appears to depend upon speculation, hearsay or otherwise incompetent evidence. Conclusions based on competent factual or opinion evidence would, however, clearly carry greater weight.
 A final, but most significant, difficulty in considering the evidence presented to us concerned the state of the knowledge on the part of the appellants about the circumstances of the murder at the time they were interviewed by the police. It is nowhere apparent in the papers, nor from the evidence presented before us, what the appellants' precise state of knowledge about the circumstances of the murder is said to have been. At times it appears to be suggested that the police put words into their mouths, and at other times that they simply responded to repeated questioning by producing information, which may or may not have been already within their knowledge. We are wholly unable, from the evidence of the appellants (so far as it can be understood) at the trial, or from the various statements made by the appellants subsequent to the trial, to discern what information was known to the appellants at the time they made the statements to the police, and what was not, and was therefore (according to the appellants) supplied by the police. The burden of the cross examination of the police at the trial appears to have been directed at demonstrating that the police put pressure on the appellants to disclose what was publicly known about the murder, not that the police fed the appellants with information. Throughout the trial therefore, and at the original appeal, the stated position of both appellants through their counsel was that all of the information which they produced in their statements to the police was public knowledge, a position which was manifestly incorrect. This does not necessarily of itself mean that the appellants' position is untenable, but the situation is unsatisfactory. As an evidential matter that goes to the heart of the appeal, it is disappointing that after all this time and effort, the position is still unclear. However, what is clearly the most significant part of the evidence in this case is concerned with the special knowledge content of the confessions by the appellant. If it can be sufficiently demonstrated that what was said by the appellants demonstrates their complicity in the murder, it cannot be said that their confessions were unreliable.
Special knowledge content of confessions
 Despite some minor contradictions, the two confessions given by the appellants on the same day at separate police stations were remarkably similar and included a number of distinct matters. Some of these matters were public knowledge, others were known or may have been guessed by the police. However the trial judge in his charge (and in his various reports) pointed out the significance of the fact that detailed and matching admissions (with some minor discrepancies) had been given by the appellants at about the same time in different locations. He also pointed to three particular features about the findings which were unusual, and which might only have been known to persons who had been intimately involved in the murder.
 First, the explanations provided by the second appellant explained the scratches found on the victim's back, when he indicated that the body had been dragged down the hill through some bramble bushes. While the scratches might have been limited to some form of contact with the bramble bushes in the minds of the investigating officers, the statement by the second appellant to the effect that they had attempted to hide the body by dragging it down the hill provided for the first time a clear explanation of how the scratch marks came about.
 Second, at the end of his first confession, Iain Murray was asked to make a sketch of the body, which he did. His sketch not only indicated the correct posture in which the body was discovered, but set it in the correct alignment in respect of the steep hillside on which it was found. There had been some suggestion that the publication in the press of a body outline in another matter might have explained the accuracy of the drawings, but that outline appears to have been inclined at an almost horizontal angle and was very different from that provided by Iain Murray, which correctly lined the body up and down the slope. Further, when compared with the sketch (which was admittedly crude), the police photograph of the body was strikingly similar, particularly in the disposition of the deceased's arms and legs. This seems to us to be a crucial part of the second appellant's confession and indicates a knowledge of the circumstances of the murder on the part of someone who must have been closely connected with it. The only other possibility is that the police accurately described the exact posture and position in which the body was found and the angle to which it was inclined to the slope, and then persuaded the appellant to repeat that information in the form of a sketch. Having regard to the circumstances and to the time involved, we consider that such an explanation seems extremely unlikely. It has never been suggested that this is what happened. In addition, it must be recalled that Iain Murray in his precognition to his own agents while on remand at Longriggend indicated that he had "made up" the sketch off the top of his head (Appendix C:16); there was no suggestion at that time by him that the details of the way in which the body lay when it was discovered had been transmitted to the second appellant by anyone else. We consider that this piece of evidence alone would have justified his conviction.
 Third, a most unusual feature of the case was that while all of the victim's clothes apart from her socks had been taken off, her wrists were above her head and still in the sleeves of her anorak. Iain Murray in his first full confession gave a credible explanation which accounted for how this came about. He described how the anorak was put back on the victim and how she was dragged down the slope. This account therefore provided for the first time an entirely plausible explanation of how the deceased's wrists came to be in the sleeves of her anorak. Again, this could be described as coming only from someone who was present at the murder.
 Finally, the appeal court in 1986 noted the remarkable similarity of the appellants' confessions, given at the same time but in different locations, and that the homosexual activities of the appellants, and their apprehension of discovery, provided for the first time an explanation for what had hitherto been regarded as a motiveless murder and that their accounts were "redolent of having been made by someone who had been present when the crime had been committed." With these characterisations of the evidence we agree.
Status of additional evidence
 We have to consider next the status of additional evidence. In terms of Section 106(3)(a) of the Criminal Procedure (Scotland) Act 1995 the High Court may review a conviction based on the existence and significance of "evidence which was not heard at the original proceedings". The way in which any new evidence is to be treated has been described in several cases.
"First, the governing question in any appeal based on additional evidence is whether the fact that it was not heard at the trial represents a miscarriage of justice. It is not a matter of whether the additional evidence is significant, ... but whether it is of such significance as to lead to the conclusion that a verdict reached in ignorance of it must be regarded as a miscarriage of justice ... while it is convenient to describe the judicial approach to determining whether it is of that significance as a 'test' it should not be forgotten that the sole test laid down by section 106(3)(a) is that of miscarriage of justice ... the 'significance' of additional evidence includes considerations as to relevance, materiality and importance, (which includes) its quality in point of credibility and reliability ... the cogency of the additional evidence is of critical importance (Kidd v H.M. Advocate 2000 J.C. 509; 2000 S.L.T. 1068; 2000 S.C.C.R. 513 -."
 The position was more particularly summed up in Megrahi v H.M. Advocate 2002 JC 99; 2002 SLT 1433; 2002 SCCR 509 (paragraph 219).
"... (1) The Court may allow an appeal against conviction on any ground only if it is satisfied that there has been a miscarriage of justice.
(2) In an appeal based on the existence and significance of additional evidence not heard at the trial, the court will quash the conviction if it is satisfied that the original jury, if it had heard the new evidence, would have been bound to acquit.
(3) Where the court cannot be satisfied that the jury would have been bound to acquit, it may nevertheless be satisfied that a miscarriage of justice has occurred.
(4) Since setting aside the verdict of a jury is no light matter, before the court can hold that there has been a miscarriage of justice it will require to be satisfied that the additional evidence is not merely relevant but also of such significance that it would be reasonable to conclude that the verdict of the jury, reached in ignorance of its existence, must be regarded as a miscarriage of justice.
(5) The decision on the issue of the significance of the additional evidence is for the appeal court, which will require to be satisfied that it is important and of such a kind and quality that it was likely that a reasonable jury properly directed would have found it of material assistance in its consideration of a critical issue at the trial.
(6) The appeal court will therefore require to be persuaded that the additional evidence is (a) capable of being regarded as credible and reliable by a reasonable jury, and (b) likely to have had a material bearing on, or a material part to play in, the determination by such a jury of a critical issue at the trial."
Conclusions: first ground of appeal
 We are far from satisfied that Professor Gudjonsson's evidence would have had any material effect on the jury's verdict in this case. We started from the premise that Professor Gudjonsson is accepted, particularly for our purposes by Professor Cooke, as the leading expert in the theory of false confessions, and the tests which he has devised are widely used throughout the United Kingdom and in many other jurisdictions. He has given evidence in many cases, is widely consulted, and it is accepted on all sides that his views command respect. We concluded that his opinion on the vulnerability of each of the appellants was justified and required to be considered carefully. However, we were of the view that it did not follow in this case that the undoubted vulnerability of the appellants at the time of their police interview meant that their statements were not reliable. We were not convinced that the new evidence was of such significance, in all the circumstances of the case, that had it been available to the jury they would have been bound to acquit. Equally, we were not satisfied that even if the jury had not fully accepted Professor Gudjonsson's opinion they would have found his evidence of material assistance in their consideration of a critical issue at the trial. As noted in HMA v Gilmour at para , new evidence must all be set in the context of the trial. We therefore have to take into account all the other relevant evidence and information bearing upon the position of the appellants, even if that evidence and information (all of which was available to Professor Gudjonsson) was not produced at the trial but only emerged subsequently. However, even discounting such additional material, and simply placing Professor Gudjonsson's opinion in the context of the evidence given at the trial, we are not satisfied that it would have had a material bearing on the jury's consideration of the case.
 Firstly, we consider that there is a significant limitation in this case to the value of the Gudjonsson Compliance Scales 1 and 2. It is plain that the purpose of the tests will be entirely transparent to the subject, and the results can therefore be easily faked. The tests essentially depend for their completion on self-reporting by the subject. In a forensic setting, such as in the present appeals, it would be unrealistic to expect the subjects to answer the questions in these tests in a fashion which was not designed to serve the purposes of the appeal. For the test to have any value, it would require to be supported by extensive, significant and direct access to contemporary sources (such as family, friends and workmates) to confirm the results. In this respect we accept the evidence of Professor Cooke. This sort of corroboration was not in any substantive or meaningful sense available in the present case. We also think that it is particularly unhelpful and artificial to ask a subject, in the context of a criminal appeal, to undertake to answer the test as he would have done more than fifteen years earlier. No scientific basis justifying such an exercise was provided. This is particularly so in the case of Brian Wilson, who was at the time of the murder reported to be of borderline intelligence. The Gudjonsson Compliance Scale therefore appears to us to be considerably less sophisticated and useful in a forensic situation than, for example, the Gudjonsson Susceptibility Scale tests. While other tests indicated that both Brian Wilson and Iain Murray were vulnerable, and susceptible to leading questions and to pressure, they also returned scores within normal limits in the Gudjonsson Suggestibility Scale tests, and Iain Murray was within normal limits in the Gudjonsson Compliance Scale test. Insofar as Professor Gudjonsson's conclusion that Brian Wilson's confession was unreliable are based on the Gudjonsson Compliance Scale, we find the value of that conclusion substantially diminished. While Professor Gudjonsson accepted that his compliance tests had limitations, as we have already noted, it was unclear what effect this concession had on his conclusions.
 Secondly, we took into account that the conclusions which Professor Gudjonsson has reached with his various measurement devices were based on the premise that the appellants were credible and reliable This view seems to depend entirely on the conclusions drawn by Professor Gudjonsson that the confessions were unreliable for the reasons which he has given in his various reports, principally that the appellants were vulnerable, and that what they said to the police had the hallmarks of a forced or "coerced-compliant"confession. However, no attempt has been made to test objectively the appellants' veracity. The issue of the appellants' vulnerability was before the jury; indeed that was the basis of their defence. The jury rejected them as incredible, and believed the prosecution case. This view of the evidence was echoed by the trial judge, who noted that the evidence of the police witnesses, despite a sustained attack on its reliability and truthfulness, was impressive, and that the appellants struggled in the witness box to explain their apparently detailed knowledge of the murder. No attempts have been made to reinterview the prosecution witnesses. In these circumstances, we approach Professor Gudjonsson's conviction that the appellants are credible and reliable with some caution.
 Thirdly, Professor Gudjonsson's conclusions depend on some further important assumptions. For example, it was assumed that police officers supplied significant amounts of information to each of the appellants about the circumstances of the murder, and about what the appellants themselves were saying in the respective police stations, despite police denials, and also in the face of an absence of clear confirmation from the appellants themselves that this sort of thing had taken place. We have already given examples of this.
 Fourthly, we were given no convincing explanation for the failure to acknowledge certain important parts of the evidence which did not fit Professor Gudjonsson's conclusions. One of the hallmarks of this kind of confession, according to Professor Gudjonsson, and endorsed by Doctor Macpherson, is that the false confession is retracted immediately the pressure which produced it is removed, typically when the subject first sees his solicitor, yet both Brian Wilson and Iain Murray each separately repeated their confessions to their parents, after they had made their admissions to the police. This perhaps could be explained by the fact that a police officer was present at each interview. But no satisfactory explanation in our view was tendered as to why Iain Murray should then make a detailed further confession (despite his poor verbal memory as revealed in the tests) to two independent police officers after being advised in the strongest and clearest terms not to do so by the duty solicitor. No satisfactory explanation is offered as to why Iain Murray subsequently admitted his guilt to his own solicitor some time later. No satisfactory explanation was offered to account for Brian Wilson's statement to a prison governor in 1990, which demonstrated an intimate knowledge of the circumstances of the murder many years into his sentence. Professor Gudjonsson said that it was highly probable that Brian Wilson was under pressure at the time, but this claim was entirely speculative and there was no identifiable pressure that was apparent, and none spoken to by the appellant. The lack of convincing explanations for these matters must in our view diminish the value of Professor Gudjonsson's conclusions.
 Fifthly, there was no detailed or satisfactory examination or explanation by Professor Gudjonsson, or by the Commission, of the special knowledge content of the confessions. This is of particular significance; the special knowledge content of the confessions, especially those of Iain Murray, was the entire basis of the convictions under appeal, and might be thought to have merited more attention than the mere dismissal of such knowledge as having inevitably been supplied by the police. The line taken by the defence at the trial was that all of the information spoken to by the appellants in their confessions was public knowledge, although there was also some suggestion that the police had put words into the appellants' mouths. But neither appellant has explained, either to the Commission or to the Court, what he himself actually knew, and what information was supplied to him by the police. Both appellants admitted during their police interviews at about the same time that they engaged in homosexual activity. It is not denied that they made these admissions. The interviewing officers could not have known that a few hours later, Doctor Gourlay would be in a position to report that Brian Wilson demonstrated signs of recent homosexual activity. This finding provided a clear and particular motive for the murder for the first time in the investigation, and was also something which could not possibly have been known to the police in advance of the interviews. It also confirmed the truthfulness of a crucial point of the confession given by Brian Wilson to the police. We find it difficult to understand why this compelling piece of evidence should be ignored. Again, Iain Murray's explanation of how he and Brian Wilson dragged the body down the hill in an attempt to hide it explained, again for the first time, both the scratches on the victim's back and the fact that her wrists were still in the sleeves of her anorak. But, above all, Iain Murray's knowledge of the posture in which the body was left, aligned up and down the hillside, and with the legs and arms both outstretched below and above the body, which he specifically explained to his solicitor when on remand at Longriggend that he had made up off the top of his head, is information which, in the circumstances of this case, clearly could only have come from someone who was present at the time of the murder, and is based on information which Iain Murray specifically refutes (by implication) that he was given by the police. There is no suggestion that he did not draw the sketch, or that he drew it according to promptings from others. The position of the body is particularly striking and could not have been guessed at. The only possible alternative explanation hinted at - that Iain Murray may have seen a billboard showing a body outline in a wholly different posture in another context - we reject as wholly unconvincing. This compelling piece of evidence, properly understood, could in our view never be disregarded in any responsible forensic examination of the case, and is in our view sufficiently decisive by itself to justify the conviction. It is therefore not enough for the appellants to say that because they are vulnerable, and that vulnerable persons make unreliable confessions, then the present confessions are unreliable. There is no reason to regard these confessions as unreliable if the indications are that they are truthful and correct. We are fully satisfied that there are elements in the admissions made by the appellants which indicate a sufficient degree of special knowledge which, at the least, required an explanation from the appellants, and in the absence of such an explanation is capable of establishing the guilt of the appellants.
 Accordingly, in terms of what is said in the cases of Kidd and Megrahi, we are not satisfied that the new additional evidence (essentially that of Professor Gudjonsson) has satisfied the relevant tests. We are not satisfied that the original jury, if it had heard Professor Gudjonsson's evidence, would have been bound to acquit. Nor in our view can a verdict reached in ignorance of that evidence be regarded as a miscarriage of justice. We consider that the jury would have found Professor Gudjonsson's evidence relevant; it was on the basis of the appellant's vulnerability that the defence was presented to the jury. But we do not think that it would be reasonable to conclude that the verdict of the jury, reached in ignorance of its existence, must be regarded as a miscarriage of justice. In particular, we think that the additional evidence, properly analysed and considered in the circumstances of the case, would not have been of such a kind and quality that a reasonable jury properly directed would have found it of material assistance in its consideration of a critical issue at the trial. We have accepted that the appellants were vulnerable, and susceptible to pressure applied by the police during interviews. But that issue was clearly understood (although perhaps not so comprehensively as now explained by Professor Gudjonsson), and squarely placed before the jury at the trial. For reasons which may be reflected in the trial judge's reports, the jury rejected the notion that the confessions were unreliable. Standing our reservations in this case about Professor Gudjonsson's conclusions, we do not think that his evidence might have persuaded the jury to a different view. Further and most significantly, we consider that the content and character of the confessions are truly redolent of complicity in this crime, and that is incompatible with the view that those confessions are untruthful, or, in the event, unreliable. We should make it clear that we consider that this case is very different on its facts from the case of Gilmour, when the evidence of Professor Gudjonsson clearly satisfied the relevant tests. In the circumstances we reject the first ground of appeal for both appellants.
Remaining grounds of appeal
 The remaining grounds of appeal can be dealt with briefly. The original second ground of appeal for both appellants criticised that part of the judge's charge to the jury which was concerned with the position of the defence. The trial judge directed the jury that the appellants' position amounted to "some sort of collusion" amongst up to ten different policemen. Further, the trial judge suggested that there had been a failure on the part of defence counsel to put that position to two of the senior police officers who had been called as witnesses. This, it was argued, was unfair and suggested that the defence had to go further than was necessary in order to raise a reasonable doubt about the guilt of the accused. In our view, there is nothing in this ground of appeal. The trial judge's directions accurately reflected the different positions adopted by the Crown and the defence at the trial. The jury were presented with a straight and clear choice; either the appellants were telling the truth and the police were lying, or the police were telling the truth and the appellants were lying. If the police were lying then clearly they were doing so in collusion with each other. In these circumstances we cannot see how the directions complained of can amount to a miscarriage of justice.
 The third original ground appeal for Brian Wilson was to the effect that he and Iain Murray had been cautioned and charged in each other's presence. This was said to be an error which constituted a miscarriage of justice. However, no significant use was made of any admission made following caution and charge, and no miscarriage of justice can therefore be identified.
 Both appellants lodged a supplementary ground of appeal. This was to the effect that in seeking a conviction for murder, the Crown relied on the admissions made by the appellants. Standing that the appellants' defence rested on the contention that these admissions were unfairly obtained, it was argued that the trial judge should have held a trial within a trial in order to ascertain whether or not in fairness to the appellants the statements and confessions should have been admitted. It is accepted that the jury were directed that the question of fairness was a matter for them to consider, and that while that was the common and accepted practice at the time it was argued that in the present day such an approach was incompatible with the appellant's right to a fair trial. We have no hesitation in rejecting this ground of appeal. For such a ground to succeed, it would have to be at least suggested that the outcome of the trial might have been different if the question of admissibility had been considered in the manner suggested. No submission to this effect was made. Further, in the event, it is clear that even if a trial within a trial had taken place, the evidence of the admissions would still have gone to the jury. The trial judge in his reports on the case made it clear that he found the evidence of the police officers who spoke to the confessions to be convincing, and that both appellants struggled in giving evidence to explain how they came by the special knowledge features disclosed in their admissions. In those circumstances, it is inconceivable that the judge would have kept the admissions from the jury. This view is reflected in the opinion of the original appeal court.
 Finally, a further supplementary ground of appeal was lodged by Iain Murray in the course of the hearing. This was to the effect that the judge should have charged the jury that a verdict of culpable homicide was available to them as an alternative to murder, and appears to have been lodged following the decision in the case of Ferguson v HM Advocate  HCJAC 71; 2009 SCCR 78. However, we are not satisfied that that decision can be properly applied to a case of this kind. There was throughout the evidence given at the trial, in the speeches of the prosecution and defence, and in the judge's charge, no perceptible basis on which a verdict of culpable homicide could be considered. No justification for such a verdict was suggested to us. While the case of Ferguson may suggest that the approach now to be taken in murder trials is that the jury should, in certain circumstances, be offered an alternative verdict of culpable homicide, the position must be very different when viewed retrospectively. The failure to give such a direction must be shown to have amounted to a miscarriage of justice. As a verdict of culpable homicide was not in the rational contemplation of anyone involved in the trial at the time, and as no justification for such a verdict is evident now, it is difficult to see how the failure to give such a direction can possibly be criticised.
 In all these circumstances we reject the remaining grounds of appeal, and accordingly the appeal for each appellant is refused.