APPEAL COURT, HIGH COURT OF JUSTICIARY
 HCJAC 52
Appeal No. XC613/05
OPINION OF THE COURT
delivered by LORD ABERNETHY
REFERRAL BY THE SCOTTISH CRIMINAL CASES REVIEW COMMISSION
in the cause
STUART MITCHELL GAIR
HER MAJESTY'S ADVOCATE
Act: W.G. Jackson, Q.C., Ms. S. Livingston; John Macauley & Co., Glasgow
Alt: M. Stewart, Q.C., A.D., Ms. Gianni; Crown Agent
11 July 2006
Introduction and background
 On 30 August 1989, after a five day trial in the High Court at Glasgow, the appellant was convicted of a charge of murder. The charge was in the following terms:-
"On 11 April 1989, in North Court Lane, Glasgow ... you STUART MITCHELL GAIR and WILLIAM McLEOD did assault Peter Dewar Smith, 3 West Plean Cottages, West Plean, Stirling and did strike him on the chest with a knife or similar instrument whereby he sustained injuries from which he died in Glasgow Royal Infirmary on 29 April 1989 and did murder him."
The verdict was a majority one.
 The appellant was sentenced to imprisonment for life.
 On the morning the trial was due to start the Crown withdrew the libel against the co-accused, William McLeod. He was later led in evidence by the Crown.
 The appellant did not appeal against his conviction. He did, however, petition the Secretary of State on more than one occasion and, following the creation of the Scottish Criminal Cases Review Commission in 1999, made an application to the Commission for review of his conviction. On 11 November 1999 the Commission referred the case to the High Court of Justiciary in the exercise of its powers under Part XA of the Criminal Procedure (Scotland) Act 1995. The Commission gave a number of reasons for the referral.
 Thereafter a number of grounds of appeal were lodged on behalf of the appellant. These were later substituted by amended grounds of appeal and on two occasions thereafter what were described as additional grounds of appeal were allowed to be received. The appellant was liberated on bail on 29 September 2000.
 Although the grounds of appeal are elaborately framed, they are only four in number. The first of these was to the effect that four witnesses whose evidence the Crown relied on at the trial had now admitted to having given perjured evidence at the trial in their identification of the appellant as being at the locus of the crime. These witnesses were William McLeod (the former co-accused), Brian Morrison, David George Cairney Smith and Alan John Gillon.
 The question of identification was the principal issue. The case for the Crown was that the appellant was in the centre of Glasgow on the night of 11 April in the company of McLeod. Although McLeod changed his evidence a number of times, his ultimate position was that, after meeting the deceased in Buchanan Street Bus Station, he and the appellant had gone with him to the lane which is the locus of the crime charged. He spoke to seeing a knife in the appellant's hand. When he saw that he ran away. He said that he heard a moan behind him. The Crown invited the jury to accept that this was due to the deceased being stabbed by the appellant. The witnesses Morrison and Smith, both teenagers, who were in the company of another boy Andrew Learmonth, gave evidence as to seeing in the lane men who had earlier been in the bus station, and gave descriptions of them. They also gave evidence that shortly afterwards two of the men they had seen ran from the toilets in St. Vincent Place. Neither of them identified either the appellant or McLeod at their respective identification parades. At the trial Morrison identified both McLeod and the appellant as being the two men, and Smith identified the appellant as one of the men in the lane. Learmonth identified McLeod as one of those men but did not identify the appellant. The witness Gillon gave evidence that he was sitting in his car and saw two men, whom he later described, in the lane standing by what he described as a bundle on the ground and then running off. He identified one of them as the appellant. Two police officers, Constables Shirley Marnock and Lewis Fulton, gave evidence identifying the appellant as being in Gordon Street, not far from the locus, shortly after the alleged attack took place. He was with another man whom P.C. Marnock identified as McLeod. The body of the deceased was found near the toilets in St. Vincent Place at about 11.20 p.m.
 The appellant's defence was one of alibi. He said that at the time of the murder he was at an address in another part of Glasgow and in the company of others.
 On 28 January 2003 the Court heard submissions from counsel. Senior counsel for the appellant invited the Court to hear further evidence from the four witnesses referred to at paragraph  above. He also invited the Court to hear the evidence of Hector McLeod Wood, who did not give evidence at the trial but whose evidence would be relied on to support the explanation why these witnesses did not give the evidence at the trial that they now wished to give. Having heard the Advocate depute in reply the Court decided that, sitting as a bench of three judges, it would hear the evidence proposed to be given by the four witnesses, together with the evidence proposed to be led from Wood. The Crown would be afforded the opportunity to lead relevant evidence in response.
 That evidence was heard by the Court on various dates in 2004 and 2005. By interlocutor dated 7 June 2005 the Court refused this ground of appeal. The appeal was continued for a hearing on the remaining grounds of appeal, which are numbered 2, 3 and 4.
 These are to the following effect:-
(2) That the Crown had failed to disclose material information to the defence prior to or at the trial. This information consisted of (i) previous statements to the police given by the witnesses Alan John Gillon, Brian Morrison and P.C. Shirley Marnock, which were at variance with the evidence that they gave at the trial relating to their identification of the appellant; and (ii) information of a personal nature in relation to Brian Morrison. This information was of paramount importance to the defence given that identification of the assailant was the critical issue at the trial. All three witnesses had identified the appellant in court. Furthermore, Brian Morrison was the only civilian witness to identify both the appellant and the former co-accused, McLeod.
(3) The conduct of the Crown in arresting the former co-accused McLeod on the instructions of the Advocate depute and having him charged with perjury in respect of evidence he had given earlier in the day exculpating the appellant and thereafter, following his recall to the witness-box the next day and giving evidence incriminating the appellant, liberating him and taking no further proceedings against him amounted to an inducement to him to change his evidence.
(4) The appellant's representation was defective in two respects, namely:-
(i) the appellant's special defence of alibi was not properly presented in
court in that a crucial witness, Hector McLeod Wood, was not called; and
(ii) there was a failure to examine properly the medical and scientific
 It was these grounds of appeal that were argued before us. We take ground (2) first.
Submissions of counsel
 Senior counsel for the appellant started by submitting that this case was very much on all fours with the case of Kidd v H.M. Advocate S.C.C.R. 200. In that case the appellant and another man were charged with murder by stabbing. The Crown case depended entirely on eye-witness evidence. There was evidence from various witnesses as to which of the accused had actually stabbed the deceased, but only two of them spoke to the appellant having done so. In particular, one witness, P, who gave evidence that the appellant had stabbed the deceased, had previously given a number of inconsistent and contradictory statements to the police as to whether or not she had seen the appellant stab the deceased. Both accused were convicted of culpable homicide, and the appellant's appeal against conviction was refused. The case was subsequently referred to the High Court by the Scottish Criminal Cases Review Commission on the ground that the failure by the Crown to disclose the police statements of P and other witnesses may have led to a miscarriage of justice. In the appeal the Crown conceded that P's statements should have been disclosed but submitted that the failure to disclose them had not led to a miscarriage of justice, there being evidence of another eye-witness incriminating the appellant, and the principal statement by P exculpating the appellant having been made when she appeared to be under the influence of medication or a drug. It was held by the Court that it was clear that there were material contradictions and inconsistencies between P's evidence and the statements she had made to the police, that bearing in mind that the Crown relied on the evidence of P, one of the two essential eye-witnesses, as being credible and reliable, disclosure of her police statements would have been likely to have been of real importance to the defence by tending to undermine the credibility and reliability of her evidence and thereby casting reasonable doubt on the Crown case, and that the failure to disclose her statements resulted in a miscarriage of justice. The appeal was allowed and the conviction quashed.
 Counsel submitted that it was therefore enough if the prior statement or statements of just one witness would have tended to undermine the credibility and reliability of that witness's evidence and thereby cast reasonable doubt on the Crown case. The structure of this case was as follows. The Crown case could not succeed if the jury did not accept McLeod's evidence incriminating the appellant. He was, however, as the trial judge put it in his report to the appeal court, an appalling witness. He changed his evidence a number of times. It was therefore crucially important to test McLeod's evidence incriminating the appellant by reference to the evidence of other witnesses who placed the appellant at the scene of the crime in the face of his alibi defence. In this context the evidence identifying the appellant as being at or near the scene at the material time was critical. The Advocate depute made that clear in his closing speech to the jury. He had there described the question of identification as what the jury might feel was "the main, if not the only, issue in this case" (page 490E of the transcript). The Crown therefore needed at least one of these other witnesses to corroborate McLeod's evidence that the appellant was at the locus at the material time. As the trial judge said in his report, this was not only important in relation to the identification of the appellant as having been there at that time but was crucial in relation to the question of the reliability and credibility of McLeod's evidence. The credibility and reliability of the evidence of the witnesses who identified the appellant as having been at the locus at the material time was therefore equally crucial. There were five witnesses who identified the appellant as having been in the centre of Glasgow at various times on the evening in question. Of these David Smith had disappeared and could not be traced. It was probable that he had given one or more police statements but these had never been made available. P.C. Lewis Fulton was now deceased. P.C. Shirley Marnock's evidence was not available because the relevant tape had been lost. That left Alan Gillon and Brian Morrison. In his evidence in chief Gillon, a 25 year old trainee funeral director, said that he was sitting in his parked car in a lane opposite the locus (North Court Lane, which runs south off St. Vincent Place in the centre of Glasgow). He said he saw what he described as a bundle on the pavement (apparently the deceased) and two people near it. One of them was a person with black hair, wearing a black leather jacket, denims and very white training shoes. Shortly thereafter he said he saw this person run out of North Court Lane into St. Vincent Place, turn left and head (in a westerly direction) along St. Vincent Place towards Buchanan Street. He then lost sight of him. He identified the appellant as that person. He had previously (about a week after the incident) identified him at an identification parade. He was cross-examined as to the reliability of that identification having regard to where he was in relation to what he said he saw, the state of the street lighting at the time (it was about 10.45 p.m., he said), the nature and quality of the view he had of the person's face and the degree of attention he was paying but insisted he was not mistaken in his identification of the appellant. He had accepted in his examination in chief that he had on 15 April given the police a statement as to what he had seen on the night in question but that statement was not a production and he was not cross-examined on its contents.
 Brian Morrison was 19 at the time. He said he was a male nurse. He said he was in the vicinity of the locus between 11 and 11.30 p.m. on the evening in question. As he was walking along St. Vincent Place (in a westerly direction) from George Square towards Buchanan Street he looked down the lane (apparently North Court Lane) and saw what he described as "an old guy ... about 50" and "two young boys ... between 20 and 25". He thought that the last two were the same height, about 5 feet 10 inches. He thought that they both had dark leather jackets on. He thought they were wearing training shoes but could not remember anything about the colour of them. He said that about 5 or 10 minutes later he saw two males run from the direction of the lane to the public toilets about 100 metres or so to the west in St. Vincent Place. He thought it was the same two young men he had seen earlier. He then saw them come out of the toilets and go back quite fast in the direction of North Court Lane. He identified them as the appellant and McLeod, who by this time was sitting in the public benches in the court. His identification was challenged in cross-examination generally in the same way as Gillon's identification of the appellant had been. He said he got a good look at the two young men. He studied their faces carefully, so that if he had seen them at any time between the incident and the trial he would have been able to recognise them without difficulty. It was then pointed out to him that at the identification parade a week after the incident he had not picked out the appellant, although he was there. He had picked out a stand-in instead. He gave no explanation for this. That passage in his cross-examination marks the end of the transcript of Morrison's evidence but it is not certain that that was the end of it. There is no note to that effect in the transcript and the court minutes do not assist, but it is stated in the transcript that the notebook containing the evidence of the succeeding witnesses, including P.Cs Lewis Fulton and Shirley Marnock, is missing. It may be, therefore, that that notebook also contained the last part of Morrison's evidence.
 Against this background counsel turned to the police statements of these witnesses that are now available. There were two statements from Gillon, the first dated 14 April 1989 and the second 9 May 1989. In the first statement, in describing the person said to be the appellant Gillon said his height was 5 feet 6 inches or 5 feet 7 inches, later corrected to 5 feet 8 inches or so. In the report of the identification parade held on 18 April 1989, however, the appellant is described as 6 feet 0 inches - 6 feet 1 inch tall. In his second statement Gillon referred to his previous statement and continued:-
"However, there are a number of things which I did not tell you about in my earlier statement because I was terrified. I would now like to tell the truth, not that I have lied to you previously, I just didn't tell you everything but it has been playing on my mind especially when the guy died."
He then went on to give an account of events not very different from what he said in evidence.
 Morrison had given four police statements. The first was given early on 12 April 1989, just an hour or so after the event which is the subject of the charge. Counsel said that it was common ground that much of what was in the statement was some kind of fantasy. Morrison had said in evidence that he was in occupation as a male nurse. Now he said he was homeless. He said that one of the two young men who ran out of the lane had shouted at him: "Morrison ... if anything happens or if you see anything going on don't open your mouth or else you're gonna die.". He said that they then pushed him to the ground and told him to go away and they ran back into the lane. He described the two men as being 5 feet 10 inches tall. He definitely knew the one who had mentioned his name but he couldn't remember where from. He then remembered that he might have been called Ian and he went on to say certain things he claimed to know about him. He said he would definitely be able to identify the two men again.
 Later on 12 April, at 3 p.m., he gave the police a second statement. In that statement he gave an account of how he knew the man he called Ian and of his dealings with him and he stated that Ian was one of the two young men involved in the incident at the locus the previous evening. His account of what Ian did at that time was the same that he had given earlier.
 On 21 April 1989 he gave the police another statement. In that statement he said:
"I have come up here to sort out the matter and I have to tell you that a lot of what I have already told the police is not the truth and I made up some of it to attract attention to myself. I'm sorry for all the trouble I've caused. I know I've done wrong but I cannot go on like this pretending I saw things which didn't happen. I have done things like this before to attract attention to myself, and once I started it I carried on because I thought I would go to jail and I don't want that. I did come into the town that night and I did hear the shout in the lane. I did see the old guy and the two men I described before but I made up the bit that one of them threatened me and said my name. Once the police started to interview me I had to come up with a name and I said it was the guy Ian who I later picked out by photograph. I said it was him because of all the trouble he has caused me and I knew he always did the poofs up at the toilets. I kept up the pretence to avoid getting into trouble with the police. I did see two people going into the toilet but I don't know if it was the same two men in the lane. The person I picked out at the parade I thought I knew him but I'm not sure. I really am sorry for telling lies and wasting your time. I cannot tell you any more."
 Counsel submitted that with this information counsel at the trial could have cross-examined Morrison in such a way as to show that the jury could not trust a word he said. He had been so unsatisfactory that on 2 June 1989 the police had interviewed him on tape under caution. That was his fourth statement. The picture of him presented by the Crown in evidence was dramatically different in the light of what was in these statements. Counsel also reminded us of Morrison's demeanour when he gave evidence in this Court in May 2004 in connection with the first ground of appeal. Faced with any difficult question he had burst into tears.
 Counsel also pointed out that attached to his Crown precognition for the trial was a note in the following terms:
"When Morrison was first cited to attend for precognition he phoned to say he had signed himself into Leverndale Hospital but that he still intended to attend. However before the date for precognition the Hospital staff phoned to tell me that Morrison had signed himself out and needless to say he didn't turn up for precognition. As a result I had to ask the police to trace him. I warned him about failure to attend to (sic) Court.
The medical staff at Leverndale Hospital are unable to give a full psychiatric report on Morrison as he was not fully examined by them. However they state that he is basically inadequate, has personality problems and has attempted suicide on a number of occasions in the past. Morrison and his vivid imagination certainly set the police off on the trail of a red herring initially."
 Counsel said that while the Crown had all this information, the defence at the trial had none of it. Morrison had been a key witness at the trial.
 In relation to P.C. Shirley Marnock, the transcript of her evidence was not available because the tape had been lost. In his closing speech to the jury, however, the Advocate depute had reminded the jury that the account given by her and P.C. Fulton was that they passed two youths in Gordon Street who were heading west (away from Buchanan Street) about 150-200 yards from the corner of St. Vincent Place and Buchanan Street shortly after the incident in question took place. P.C. Marnock said they looked uneasy. She attended an identification parade on 28 April, when she picked out the appellant. Counsel accepted that even if her (undated) police statement had been available to the defence at the trial she would not have retracted her identification of the appellant but she did give a wrong estimate of the height of the two men she said she saw - 5 feet 10 inches/11 inches for one (apparently the appellant) and 5 feet 8 inches for the other. She also thought that the second suspect was possibly another person with whom she had had dealings rather than McLeod. These were matters that could have been taken up in cross-examination.
 Counsel submitted that it could not be said that the above-mentioned material was not material which should have been made available by the Crown to the defence as tending to undermine the credibility and reliability of the identification evidence of the appellant.
 In reply the Advocate depute accepted that the Crown was under a duty to disclose information which supported any known stateable defence or undermined the Crown case. The duty of disclosure existed prior to the trial in relation to an indicated line of defence and also to such evidence as might exculpate the accused or in the mind of the jury cast a reasonable doubt on the Crown case. Further, the duty of disclosure was a continuing one which existed pre-trial and throughout the leading of evidence by the Crown. If, in the course of leading evidence, it became apparent that the Crown had information which might exculpate the accused or undermine the Crown case, then the Crown had a duty to disclose that to the defence. See Kidd v H.M. Advocate, supra, at paragraph 15.
 In relation to the three witnesses whose police statements the defence said should have been disclosed the Advocate depute submitted that there was no duty on the Crown to disclose the statements of Gillon and P.C. Marnock. That was because, viewed objectively as matters now stood, in neither case would disclosure of the statements have been material to the defence case. No miscarriage of justice had therefore resulted from the failure to disclose their statements. In relation to Gillon the defence had highlighted the discrepancy between the estimated height of the person said to be the appellant in the statement given on 14 April 1989 and the appellant's actual height as being of importance in the question of identification. But in his statement Gillon said that the person who was the appellant was in the vicinity of the locus at the material time, he saw what he described as the bundle on the pavement, which by inference was the deceased, and described two people beside the bundle, one of whom, the appellant, he identified a week later at an identification parade. In his second statement, dated 9 May 1989, he described in greater detail what he saw but it was not essentially different from the first statement and Gillon was positive that the person he had identified at the parade (the appellant) was the one of the two assailants who was wearing white shoes. The scope for cross-examination of Gillon on the basis of this statement was therefore limited. In the course of his evidence in the trial he was robustly challenged in relation to his identification of the appellant as the man with the white shoes standing beside the bundle. The height of the appellant played no part in his identification of him. According to his first statement he had also identified him from a photograph and at the identification parade he had identified the appellant at the first time of asking. There was therefore nothing lost to the defence, and in particular nothing in relation to his identification of the appellant, as a result of their not having had Gillon's two police statements. It might even have enhanced his credibility if the statements had been before the Court at the trial. Reference was made to Kelly v H.M. Advocate 2006 S.C.C.R. 9 at paragraph 33. It was to be noted that, apart from his identification evidence, Gillon's evidence in other respects of the incident was confirmed by other witnesses. In any event Gillon's evidence was but one strand in a circumstantial case. He was an important witness but without his evidence the Crown case would not have collapsed. This was different from the situation in the cases of Kidd, supra, Holland v H.M. Advocate 2005 S.C.C.R. 417 and Sinclair v H.M. Advocate 2005 S.C.C.R. 446.
 In relation to P.C. Marnock the Advocate depute said that she had said in her statement that the appellant was 5 feet 10 inches-5 feet 11 inches (as opposed to his actual height of 6 feet 0 inches-6 feet 1 inch) and she had identified him at the identification parade on 28 April 1989. Her evidence at the trial was not available because the tape had gone missing but at the hearing in relation to the first ground of appeal (on 30 November 2004, pages 774-5 of the transcript of that hearing) the discrepancy between her estimate of the height of the appellant and his actual height was put to her. She found nothing remarkable in it. She could not remember if she had any doubt about her identification of him at the parade because of his height but said that if she had had she would have said so. From her description of the other man an e-fit image had been prepared which had led to the apprehension of McLeod. In her statement P.C. Marnock had described the clothing worn by the two men and had said that they were jogging when she saw them in Gordon Street, which is what McLeod had said at the trial they were doing (page 97 of the transcript). Her statement was accurate in its salient points. The discrepancy between her estimate and the appellant's actual height would not have made any material difference. Although her evidence at the trial was not available, the trial judge in his report had said that she had identified the appellant and in cross-examination had insisted she was certain of it. At the same time as the Court heard evidence in relation to the first ground of appeal evidence was heard in relation to what was said to be fresh evidence in the form of her statement. The Court had not been persuaded that what was in the statement was "likely to have had a material bearing on, or a material part to play in a reasonable jury's determination of a critical issue at the trial". That was, of course, the test in relation to that ground of appeal. The critical issue in question was the identification of the appellant. In all these circumstances the failure to disclose her statement was unlikely to have been of any material assistance to the appellant's defence team in the preparation or presentation of his defence.
 Turning to the four statements given by Morrison the Advocate depute accepted that the statements should have been disclosed but he again submitted that no miscarriage of justice had resulted from failure to do so. He accepted that what he said in the earlier statements in relation to "Ian" was fantasy; it was false and exaggerated. In later statements he admitted he had made it up. He said he saw the appellant on the identification parade and explained why he did not pick him out. His evidence was significant in that he identified the appellant as having been at the locus. He did not say much about what had happened there but what he did say corresponded with Gillon's and McLeod's evidence of the incident. Gillon and McLeod also identified the appellant as having been at the locus. Morrison said he was in the company of David Smith and Andrew Learmonth. Smith gave a similarly corresponding account of events at the locus and identified the appellant as one of the two men who had been there with the deceased. Learmonth also gave a similar account of events. He identified McLeod as one of the two men who had been at the locus with the deceased but he did not identify the appellant. There was therefore a clear body of evidence which pointed to the accuracy of Morrison's evidence as to the appellant's being in the vicinity of the locus at the material time. Not everything in his earlier statements was fantasy. His description of the appellant consisted with the evidence of other witnesses. The man he called Ian did in fact exist (Ian May or Main) but was in custody at the time. This was known to the appellant at the time of the trial, as was the fact that Morrison had at some stage picked him out from a book of photographs: see page 436 of the transcript. It was not clear how the appellant had got this information. There was no record to show that the Crown had given them any of Morrison's statements but it might have come from a defence precognition of Morrison. However, it had never been put to Morrison in cross-examination that he had told the police that Ian May was the man he now said was the appellant. The defence challenge to his identification of the appellant came from another angle, namely, that Morrison's evidence that he had studied the faces of the two men carefully so that if he saw them again he would be bound to recognise them did not square with his failure to pick out the appellant at the identification parade (pages 205-209 of the transcript). It seemed as if Morrison's evidence did not in fact end on page 209 but may have continued into the evidence covered by the missing tape. But in his speech to the jury (pages 522-3 of the transcript) senior counsel for the appellant confined his remarks to contrasting Morrison's identification of both the appellant and McLeod in evidence with his failure to identify them at the respective identification parades, even though the defence knew that Morrison had given a statement in which he had named Ian May as the man he now said was the appellant.
 With regard to the information about Morrison's admission to Leverndale Hospital, this was just a precognoscer 's note added at the end of Morrison's Crown precognition. The precognoscer was not an expert who could comment on Morrison's personality or his psychiatric condition.
 The Advocate depute submitted that even if at the end of the day Morrison's evidence could be completely discounted, which was the best the defence could achieve, there was still ample evidence in the rest of the case to conclude that no miscarriage of justice had resulted from the defence not having had his police statements.
 Whether a miscarriage of justice had occurred was a large and difficult topic. There was no test as to what constituted a miscarriage of justice in terms of section 106(3) of the Criminal Procedure (Scotland) Act 1995 but it must be based on something specific or of some substance. It could therefore be said to be a high test. Reference was made to the Report by the Committee on Criminal Appeals and Alleged Miscarriages of Justice chaired by Sir Stewart Sutherland, Harper v H.M. Advocate 2005 S.C.C.R. 245, Drummond v H.M. Advocate 2003 S.C.C.R 108 and Cameron v H.M. Advocate 1987 S.C.C.R. 608. There was a distinction between the concept of a fair trial and the concept of a miscarriage of justice. The fact that there had been some unfairness in a trial did not necessarily mean that a miscarriage of justice had occurred. Binks v H.M. Advocate 1984 S.C.C.R. 335 was one example but there could be others. The non-disclosure of Morrison's police statements in this case fell into this category. It could not be said here, as Lord Rodger of Earlsferry had said in Holland v H.M. Advocate, supra, at paragraph 83, that the non-disclosure might possibly have affected the jury's verdict. That was because at best for the defence Morrison's evidence would be destroyed but, as submitted earlier, there was plenty of other evidence, including identification evidence, to incriminate the appellant. In Holland the dock identification in question was essential to conviction. Morrison's dock identification evidence of the appellant in this case was not essential to conviction. Sinclair v H.M. Advocate, supra, was similarly distinguishable because the evidence of the witness whose police statement had not been disclosed to the defence by the Crown was essential to the proof of the Crown case: see Lord Hope of Craighead at paragraph 34. That was also the position in Kidd v H.M. Advocate, supra. The present case was more in line with Kelly v H.M. Advocate 2005 S.C.C.R. 9.
 It is not necessary to deal at any length with the non-disclosure of Gillon's and P.C. Marnock's police statements. It is sufficient to say that, generally for the reasons given by him in his submissions to the Court, we agree with the Advocate depute that no miscarriage of justice resulted from the non-disclosure of those statements.
 The appellant's arguments in respect of Morrison's police statements are more formidable. As the Advocate depute at the trial put it in his speech to the jury, the question of identification was the main, if not the only, issue in the case. The principal witness for the Crown was the former co-accused, McLeod. He changed his position a number of times in the course of his evidence. His final position was that he and the appellant were at the locus together with the deceased. The plan had been to rob the deceased but then the appellant produced a knife. When he saw that he ran away. He said that he heard a moan behind him. The Crown invited the jury to accept that this was due to the deceased being stabbed by the appellant. McLeod therefore incriminated the appellant and he identified him. His evidence was of crucial importance to the Crown case. He was, however, an appalling witness, as the trial judge put it in his report. The trial judge went on to say that without the supporting evidence of other witnesses the jury would have had no rational basis for accepting McLeod as credible or reliable on any matter. These witnesses were Gillon, Smith, Morrison and P.Cs Marnock and Fulton. Gillon, Smith and Morrison identified the appellant as having been one of the two young men involved in an incident with the deceased at the locus. (Both Smith and Morrison had failed to pick him out at the identification parade a week after the incident). Only Morrison, however, identified McLeod as having been the other man. P.Cs Marnock and Fulton saw two young men shortly thereafter not far away, in Gordon Street. Both of them identified the appellant as one of the men but only P.C. Marnock identified the other one as McLeod. This was all eye-witness identification evidence and subject to the usual qualifications for such evidence but it interrelated both inter se and with McLeod's evidence. It therefore provided an understandable basis for accepting McLeod's final version of events.
 Morrison therefore was a very important witness even if not an essential one. His evidence was relied on by the Crown as an important part of a body of evidence which showed that the appellant was not just in the vicinity of the lane (the locus) but actually in the lane and which the jury were invited to accept as credible and reliable, the critical significance of it being that it tended to support the credibility and reliability of McLeod's crucial evidence.
 In his evidence in chief Morrison said that his occupation was a male nurse. That might be said, as counsel for the appellant submitted, to give him an air of respectability. In any event, there was nothing to suggest that he was other than a straightforward eye-witness doing his best to give credible and reliable evidence. In particular, there was no suggestion that he had given previous inconsistent statements to the police, that he was given to fantasise or that he had been in Leverndale Hospital, a hospital for the mentally ill. In cross-examination defence counsel was unable to do much more than test his identification evidence in what might be described as a basic manner for eye-witness identification, namely, by asking about the street lighting at the time and how good a view he had of the person he said was the appellant. Defence counsel was able to point out that although Morrison said he was able to study the faces of the two younger men at the incident carefully, he did not identify the appellant at the identification parade a week later. But his evidence as recorded in the transcript goes no further than that. It would appear that his evidence did not in fact end there. There is certainly no indication, as there is with other witnesses whose evidence has been transcribed, that it did. There may have been further cross-examination. There may have been re-examination. But whether there was or was not is idle speculation.
 It is true that there was a reference by counsel for the defence in cross-examination to a previous statement Morrison had given to the police but this was in the context of his questioning in relation to the identification parade where the witness was referred to "the person to whom you referred in your statement to the police" when he was asked if he saw him on the parade: see question 5 in Section D of the report of the identification parade. It is also true that by the time the appellant came to give evidence he was aware that at some stage Morrison had been shown a book of photographs and had picked out Ian May. There is no information as to how or when the appellant came by this knowledge. The Advocate depute said that the Crown had no record of having given any of Morrison's previous statements to the defence and accepted for the purposes of this appeal that they had not.
 What can be said is that in his closing speech to the jury, counsel for the appellant, when dealing with Morrison, confined himself to reminding the jury that Morrison had failed to pick out the appellant on the identification parade, picking out a stand-in instead, and warned them about the reliability of eye-witness identification in the particular circumstances.
 In our opinion there is no doubt that all four of Morrison's police statements should have been disclosed to the defence. The Advocate depute rightly accepted that that was so. These statements showed that Morrison was prepared to tell lies, to fantasise and to change his account when it suited him. The information that he had been a patient in Leverndale Hospital should also have been disclosed. If the defence had had that information there is no doubt in our minds that they would have used it. It would have painted a completely different picture of Morrison from the one the jury was presented with and would have tended dramatically to undermine the credibility and reliability of his evidence and, in particular, his identification evidence. Indeed, it is no exaggeration to say that with that information the defence could have destroyed his testimony. Non-disclosure of the information meant that there was no equality of arms between the Crown and the defence in relation to Morrison and the defence were deprived of a powerful argument on the crucial issue of identification.
 Of course, even if the jury had had the fuller picture of Morrison as revealed by this information, they might still have convicted the appellant. One cannot tell what the effect of the additional information would have been. Morrison was not an essential witness for the Crown. But he was a very important one and the fact that his evidence and, particularly his identification evidence, interrelated with the evidence of the other eye-witnesses was a point which the Advocate depute at the trial quite naturally founded upon in his closing speech to the jury. Without Morrison's evidence that point could not have been made, or at least could not have been made so cogently. In our view, therefore, the Advocate depute before us was not correct in saying that the best that the defence could hope for if they had had the non-disclosed information about Morrison was the destruction of him as a witness. It is not possible to say that without his evidence the jury would nevertheless have convicted. The Crown case, based as it was on the "appalling" McLeod and a body of other eye-witness identification evidence, was not as strong as that. So the possibility that the jury might have reached a different verdict if the police statements and other information about Morrison had been disclosed is in our view real and certainly cannot be excluded.
 Each case of course turns upon its own facts. On the facts of this case the disclosure of Morrison's police statements and the information about his admission to Leverndale Hospital would, in our opinion, have been of real importance to the defence in that it would have tended to undermine the credibility and reliability of Morrison's evidence and thereby cast reasonable doubt on the Crown case. In these circumstances we have come to the conclusion that the non-disclosure of these police statements and other information resulted in a miscarriage of justice.
 That is sufficient to dispose of this case. It is not necessary for us to deal with grounds of appeal 3 and 4. It is sufficient to say that we were not persuaded that either of them was well-founded. For the reasons we have given, however, we shall allow the appeal and quash the conviction.