England and Wales Court of Appeal (Criminal Division) Decisions

IN THE COURT OF APPEAL
CRIMINAL DIVISION

		Royal Courts of Justice The Strand London WC2
		31st July 1996

LORD JUSTICE PHILLIPS: This is the judgment of the Court, There are before the Court two appeals against conviction. In each case the Prosecution placed substantial reliance upon the results obtained by comparing DNA profiles obtained from a stain left at the scene of the crime with DNA profiles obtained from a sample of blood provided by the appellant. In each case leave to appeal was given long out of time to enable the appellant to advance arguments based on the possibility of shortcomings in the DNA evidence and the manner in which it was presented to the jury which were neither appreciated at the time of the trial nor when consideration was given to applying for leave to appeal against conviction after the trial. We have received fresh expert evidence on these matters adduced on behalf of both the Appellants and the Crown.

Before turning to the facts of the individual appeals we propose to make some general comments about DNA testing, the conclusions that can properly be drawn from such testing and the manner in which those conclusions should be presented to the jury.

DNA Testing

Deoxyribonucleic acid, or DNA, consists of long ribbon-like molecules, the chromosomes, 46 of which lie tightly coiled in nearly every cell of the body. These chromosomes - 23 provided from the mother and 23 from the father at conception, form the genetic blueprint of the body. Different sections of DNA have different identifiable and discrete characteristics. When a criminal leaves a stain of blood or semen at the scene of the crime it may prove possible to extract from that crime stain sufficient sections of DNA to enable a comparison to be made with the same sections extracted from a sample of blood provided by the suspect. This process is complex and we could not hope to describe it more clearly or succinctly than did Lord Taylor CJ in the case of Deen (transcript: 21st December 1993), so we shall gratefully adopt his description.

"The process of DNA profiling starts with DNA being extracted from the crime stain and also from a sample taken from the suspect. In each case the DNA is cut into smaller lengths by specific enzymes. The fragments produced are sorted according to size by a process of electrophoresis. This involves placing the fragments in a gel and drawing them electromagnetically along a track through the gel. The fragments with smaller molecular weight travel further than the heavier ones. The pattern thus created is transferred from the gel onto a membrane. Radioactive DNA probes, taken from elsewhere, which bind with the sequences of most interest in the sample DNA are then applied. After the excess of the DNA probe is washed off, an X-ray film is placed over the membrane to record the band pattern. This produces an auto radiograph which can be photographed. When the crime stain DNA and the sample DNA from the suspect have been run in separate tracks through the gel, the resultant auto-radiographs can be compared. The two DNA profiles can then be said either to match or not."

Even if a number of bands correspond exactly, any discrepancy between the profiles, unless satisfactorily explained, will show a mis-match and will exclude the suspect from complicity. Thus the first stage in seeking to prove identity by DNA profiling is to achieve a match.

The characteristics of an individual band of DNA will not be unique. The fact that the identical characteristic of a single band are to be found in the crime stain and the sample from the suspect does not prove that both have originated from the same source. Other persons will also have that identical band as part of their genetic make-up. Empirical research enables the analyst to predict the statistical likelihood of an individual DNA band being found in the genetic make-up of persons of particular racial groups 'the random occurrence ratio'.

As one builds up a combination of bands, the random occurrence ratio becomes increasingly more remote, by geometric progression. Thus if two bands, each of which appear in 1 in 4 of the population are combined, the combination will appear in 1 in 16 of the population, and if to these are added a further band that is found in 1 in 4 of the population, the resultant combination will appear in 1 in 64 of the population. This process of multiplication is valid on the premise that each band is statistically independent from the others. The frequency ratio of the blood group is a factor which is statistically independent and thus this can also validly be used as a multiplier. If the DNA obtainable from the crime stain permits, it may be possible to demonstrate that there is a combination of bands common to the crime stain and the suspect which is very rare. For instance, it may be that the match achieved with the crime stain is one which has a statistical probability of existing in the case of only one in a million of the populace. We shall take a match probability, or random occurrence ratio, of one in a million as an example to demonstrate the conclusions that can properly be drawn from such data and those which cannot. We shall start with the latter.

"The Prosecutor's Fallacy"

It is easy, if one eschews rigorous analysis, to draw the following conclusion:

) Only one person in a million will have a DNA profile which matches that of the crime stain.

) The Defendant has a DNA profile which matches the crime stain.

) Ergo there is a million to one probability that the Defendant left the crime stain and is guilty of the crime.

Such reasoning has been commended to juries in a number of cases by Prosecuting Counsel, by judges and sometimes by expert witnesses. It is fallacious and it has earned the title of "The Prosecutor's Fallacy". The propounding of the Prosecutor's Fallacy in the course of the summing up was the reason, or at least one of the reasons, why the appeal against conviction was allowed in Deen. The nature of that fallacy was elegantly exposed by Balding and Donnelly in 'The Prosecutor's Fallacy and DNA Evidence' [1994] CLR 711. It should not, however, be thought that we endorse the calculations on pages 715 and 716 of that article.

Taking our example, the Prosecutor's Fallacy can be simply demonstrated. If one person in a million has a DNA profile which matches that obtained from the crime stain, then the suspect will be one of perhaps 26 men in the United Kingdom who share that characteristic. If no fact is known about the Defendant, other than that he was in the United Kingdom at the time of the crime the DNA evidence tells us no more than that there is a statistical probability that he was the criminal of 1 in 26.

The significance of the DNA evidence will depend critically upon what else is known about the suspect. If he has a convincing alibi at the other end of England at the time of the crime, it will appear highly improbable that he can have been responsible for the crime, despite his matching DNA profile. If, however, he was near the scene of the crime when it was committed, or has been identified as a suspect because of other evidence which suggests that he may have been responsible for the crime, the DNA evidence becomes very significant. The possibility that two of the only 26 men in the United Kingdom with the matching DNA should have been in the vicinity of the crime will seem almost incredible and a comparatively slight nexus between the Defendant and the crime, independent of the DNA, is likely to suffice to present an overall picture to the jury that satisfies them of the Defendant's guilt.

The reality is that, provided there is no reason to doubt either the matching data or the statistical conclusion based upon it, the random occurrence ratio deduced from the DNA evidence, when combined with sufficient additional evidence to give it significance, is highly probative. As the art of analysis progresses, it is likely to become more so, and the stage may be reached where a match will be so comprehensive that it will be possible to construct a DNA profile that is unique and which proves the guilt of the Defendant without any other evidence. So far as we are aware that stage has not yet been reached.

The cogency of DNA evidence makes it particularly important that DNA testing is rigorously conducted so as to obviate the risk of error in the laboratory, that the method of DNA analysis and the basis of subsequent statistical calculation should - so far as possible - be transparent to the Defence and that the true import of the resultant conclusion is accurately and fairly explained to the jury.

The Role of the Expert

Mr Alistair Webster QC, on behalf of Doheny, has made the following suggestions as to the procedure which should be followed in relation to DNA evidence:

1. The scientist should adduce the evidence of the DNA comparisons together with his calculations of the random occurrence ratio.

2. Whenever such evidence is to be adduced, the Crown should serve upon the Defence details as to how the calculations have been carried out which are sufficient for the defence to scrutinise the basis of the calculations.

3. The Forensic Science Service ("FSS") should make available to a defence expert, if requested, the databases upon which the calculations have been based.

It seems to us that these suggestions are sound, and we would endorse them. We would add that it is important that any issue of expert evidence should be identified and, if possible, resolved before trial and this area should be explored by the Court in the pre-trial review.

When the scientist gives evidence it is important that he should not overstep the line which separates his province from that of the Jury.

He will properly explain to the Jury the nature of the match ("the matching DNA characteristics") between the DNA in the crime stain and the DNA in the blood sample taken from the Defendant. He will properly, on the basis of empirical statistical data, give the Jury the random occurrence ratio - the frequency with which the matching DNA characteristics are likely to be found in the population at large. Provided that he has the necessary data, and the statistical expertise, it may be appropriate for him then to say how many people with the matching characteristics are likely to be found in the United Kingdom - or perhaps in a more limited relevant sub group, such as, for instance, the Caucasian sexually active males in the Manchester area. This will often be the limit of the evidence which he can properly and usefully give. It will then be for the Jury to decide, having regard to all the relevant evidence, whether they are sure that it was the Defendant who left the crime stain, or whether it is possible that it was left by someone else with the same matching DNA characteristics.

The scientist should not be asked his opinion on the likelihood that it was the Defendant who left the crime stain, nor when giving evidence should he use terminology which may lead the Jury to believe that he is expressing such an opinion.

It has been suggested that it may be appropriate for the statistician to expound to the Jury a statistical approach to evaluating the likelihood that the Defendant left the crime stain, using a formula which gives a numerical probability weighting to other pieces of evidence which bear on that question. This approach uses what is known as the Bayes Theorem. In the case of Dennis John Adams (Transcript 26th April 1996) this Court deprecated this exercise in these terms at p.30:

"To introduce Bayes Theorem, or any similar method, into a criminal trial plunges the Jury into inappropriate and unnecessary realms of theory and complexity deflecting them from their proper task."

We would strongly endorse that comment.

The Summing Up

When the Judge comes to sum up the Jury are likely to need careful directions in respect of any issues of expert evidence and guidance to dispel any obfuscation that may have been engendered in relation to areas of expert evidence where no real issue exists. The Judge should explain to the Jury the relevance of the random occurrence ratio in arriving at their verdict and draw attention to the extraneous evidence which provides the context which gives that ratio its significance, and that which conflicts with the conclusion that the Defendant was responsible for the crime stain. Insofar as the random occurrence ratio is concerned, a direction along these lines may be appropriate, although any direction must always be tailored to the facts of the particular case:

"Members of the Jury, if you accept the scientific evidence called by the Crown, this indicates that there are probably only four or five white males in the United Kingdom from whom that semen stain could have come. The Defendant is one of them. If that is the position, the decision you have to reach, on all the evidence, is whether you are sure that it was the Defendant who left that stain or whether it is possible that it was one of that other small group of men who share the same DNA characteristics."

With these introductory remarks, we turn to the particular facts of the two appeals.

DOHENY

On the 8th November 1990, in the Crown Court at Manchester, the Appellant was convicted of rape and buggery and sentenced to terms of imprisonment of 8 years on each Count, concurrent. On the 9th July 1991 those terms were increased by this Court to twelve years concurrent on each Count on a reference by the Attorney General pursuant to S.36 of the Criminal Justice Act 1988. His appeal against conviction is brought with leave of the Single Judge who granted an extension of time of 4 years and 8 months.

The Facts

At about 4.30 on the afternoon of Friday 10th November 1989 a widow aged 65 was about to enter her home, having been out to visit a friend, when a man punched her in the face, seized her by the throat from behind and forced her into her house. He threatened her with a knife which he claimed to have, raped and buggered her with violence, stole her purse and left her bruised and scratched, with a bitten breast and lacerations of the vaginal and anal tissues. The assailant made sure that his victim never got a clear look at his face.

Semen stains were subsequently found on the underclothes of the victim. A pubic hair was found on the bedspread and a matching hair on the victim in the vicinity of her anus.

The case for the Crown turned largely on the DNA evidence, to which we shall turn shortly. First, however, we shall summarise the remainder of the evidence given for the Crown and the Defence. The evidence of the complainant was read to the Jury in the form of a witness statement. This included a description of the assailant. While this did not match the Appellant in every respect, there was no discrepancy that could not have been explained as an error of appreciation or recollection having regard to the complainant's description of her ordeal. She described her assailant as having a local accent. The Appellant had a local accent.

The Appellant gave evidence and denied being responsible for the assault on the complainant. He gave evidence of his movements and his whereabouts at the time of the assault, with the aid of a plan. He said that he had been in a public house playing pool and had then driven straight home to his wife without stopping. He and his wife had then left together to go to visit her father. His wife and father-in-law were called, together with other witnesses, and their evidence supported that of the Appellant as to his movements and - subject to a natural degree of approximation - his timings. The Appellant's route home would, however, have taken him quite close to the complainant's home and the evidence of these witnesses could not preclude the possibility that he might have stopped and committed the assault on his way home.

The Grounds of Appeal

The Appellant contends that the verdict of the Jury was unsafe because the forensic evidence was presented to the Jury in a misleading and inaccurate manner and because the substance of that evidence was incorrect.

The Forensic Evidence

Expert evidence was given on behalf of the Prosecution by two scientists, Miss Holmes and Mr Davie. Miss Holmes gave evidence that the two pubic hairs to which we referred earlier originated neither from the complainant nor from the Appellant. The Appellant did, however, have the same blood group as the man who had left the semen stains - a blood group shared by about 14% of the population.

Mr Davie gave evidence of the results of tests which compared the DNA found in a blood sample taken from the Appellant with the DNA extracted from the crime stains of semen. Mr Davie used two different test methods. The first employed a multi locus probe. This method was the first DNA profiling technique to be used in the United Kingdom in criminal casework. It was superseded, relatively quickly, by single locus profiling, which was the other method employed by Mr Davie.

Whichever method is used, the probe selects distinctive portions of DNA known as stutters. The multi locus probe selects a family of stutters that form a pattern from a variety of sources that cannot be identified. The single locus probe selects a pair of stutters from an identified part of an identified chromosome.

Where a match is obtained of DNA profiles by the use of the multi locus probe technique, the individual bands of DNA that form the pattern are multiplied together, on the basis that each has a value of .26, which is a conservative average of the frequency with which each band will be found in the general populace. The product is the random occurrence ratio of the matching pattern. Where matching bands are found by the single locus probe technique, a specific frequency ratio can be applied to each that is appropriate for the size of the band. These are then multiplied together to obtain the random occurrence ratio of all the matching bands, taken as a group.

The multi locus probe test produced 6 matching bands. Mr Davie disregarded one of these for a reason to which we shall revert. The product of the other 5 resulted in a random occurrence ratio of 1 in 840.

Three single locus probe tests were carried out. Two of these produced two matching bands each, the third produced one matching band. The product of these 5 bands, after applying appropriate formulae, was a random occurrence ratio of 1 in 6,900.

Mr Davie then multiplied together the results of the two tests to produce a ratio of 1 in 5.7 million. Finally Mr Davie multiplied this figure by 7, to have regard to the occurrence ratio of the blood group, to produce a final random occurrence ratio of 1 in 40 million.

When examined in chief Mr Davie explained in detail the process that we have attempted to summarise above. His examination concluded as follows:

"Q. What is the combination, taking all those into account?

A. Taking them all into account, I calculated the chance of finding all of those bands and the conventional blood groups to be about 1 in 40 million.

Q. The likelihood of it being anybody other than Alan Doheny?

A. Is about 1 in 40 million.

Q. You deal habitually with these things, the jury have to say, of course, on the evidence, whether they are satisfied beyond doubt that it is he. You have done the analysis, are you sure that it is he?

A. Yes."

The second question, in leading form, and the affirmative answer given to it constituted a classic example of the "Prosecutor's fallacy". The third question was one for the Jury, not for Mr Davie. Mr Davie gave an affirmative answer to it. It is not clear to what evidence, if any, other than the DNA evidence, he had regard when giving that answer. For the reasons that we gave in our introduction to this Judgment, this series of questions and answers was inappropriate and potentially misleading. The questions should not have been asked of this witness. If the random occurrence ratio was, indeed, 1 in 40 million this nonetheless meant that there was a statistical possibility of several individuals in the United Kingdom having the same DNA profile as the assailant, of whom one was the Appellant. It was for the Jury to decide on all the evidence whether they were sure that it was the Appellant who left the crime stain, or whether it might have been one of a handful of other persons who might exist in the United Kingdom sharing the same DNA profile.

When he came to sum up, the Judge gave an imaginative and illuminating description of the manner in which the cumulative effect of matching DNA bands and matching blood group could exclude an increasingly large proportion of the populace from consideration as the assailant. He commented:

"You could theoretically go through the population like that until you have got one person left."

He then referred the Jury to the evidence of Mr Davie and to his conclusion:

".....in the end his opinion was that his tests were reliable and they did show that the chance of Mr Doheny not being the person responsible was so remote as to be possible to discount entirely for all practical purposes."

The Judge reminded the Jury of the remainder of the evidence, including the finding of pubic hairs that were not the Appellant's, and the Appellant's alibi evidence. The overall effect of the summing up was, however, that if the Jury accepted the evidence of Mr Davie, the Appellant's guilt was conclusively established.

We have already indicated that both Mr Davie and the Judge should have left it to the Jury to weigh, on the one hand, the cogent DNA evidence coupled with the other evidence identifying the Appellant as the potential assailant against, on the other, the Defendant's evidence and that of his alibi witnesses.

Given what was then the uncontroverted expert evidence that the random occurrence ratio of the DNA profile shared by the Appellant and the crime stain was 1 in 40 million, we have no doubt that the Jury would have reached the same verdict if directed in this way. The more remote the random occurrence ratio, the less significant will be the adoption of the 'Prosecutor's fallacy', until the point is reached where that fallacy does not significantly misrepresent the import of the DNA evidence. Such was the position on the figures advanced by Mr Davie. Before us, however, Mr Davie's figures were not merely attacked, but significantly undermined.

The Attack on the DNA Evidence

On behalf of the Appellant Dr Debenham, a molecular biologist and Professor Donnelly, a statistician, were called to give evidence. On behalf of the Crown, Dr Gill and Mr Lambert respectively provided similar expertise. Three of them are highly qualified specialists in the field of DNA profiling. The fourth, Professor Donnelly, is an expert in the statistical evaluation of the results of DNA profiling.

The principal bone of contention between the experts was whether it had been legitimate for Mr Davie to multiply the result of the multi locus probe test with the results of the single locus probe tests. The Appellant's experts expressed the opinion that this was not legitimate. The reason for this is explained in the following passages collated from the written report of Dr Debenham dated the 14th June 1996:

"In a multi locus probe test the result is composed of a large number of DNA alleles from mini-satellite DNA locations of unknown origin ... Research studies have established that some mini-satellites can be clustered together in close genetic proximity.... The single locus probes, whilst separate with respect to each other may not be separate from the unknown mini-satellites detected by the multi locus probe test. As there is no way of determining in any one multi-locus probe test whether the bands identified are clustered with respect to any of the single locus probe alleles it cannot be assumed that the tests are independent."

Put more simply, there is a risk that the multi locus probe test will identify bands which are the same as those identified by the single locus probes, or in such close proximity to them that there is a likelihood that they will be linked together, so that whenever one is found the other will be likely to be present also.

The possibility of such a linkage between bands in close proximity is common ground; the degree of likelihood of this is not. Mr Davie had, in fact, discovered that one of the pair of bands identified by the single locus probe MS31 duplicated one of the bands identified by the multi locus probe. It was for this reason that he included only 5 rather than 6 bands when calculating the random occurrence ratio of the multi locus probe profile. On the second day of the appeal the experts for the Crown conceded that, after examination of the relevant material, which happily has been preserved, it seemed to them that both the MS31 probe bands were duplicated in the multi locus probe profile. This, of itself, resulted in reducing Mr Davie's final figure for the random occurrence ratio, by a factor of 4 from 1 in 40 million to 1 in 10 million.

So far as concerns the more general question of whether the approach of multiplying the results of the two tests was in any event legitimate, the experts for the Crown made a number of concessions:

1. They were unaware of any other instance where such an approach had been adopted.

2. No empirical research had been conducted which demonstrated the independence of the results of multi locus probe tests and single locus probe tests.

3. The possibility of dependence existed.

The witnesses for the Crown thought that this possibility was slight. The witnesses for the Appellant contended that, in the absence of empirical justification, the exercise performed by Mr Davie was not legitimate. However great or small the risk of dependence, that risk was not capable of quantification.

All the experts were in agreement that the result of the multi-locus probe test potentiated to a degree the results of the single locus probe tests. Our conclusion is that the extent of this is uncertain, albeit that it is likely to be significant, and that the approach adopted by Mr Davie in this case has not been demonstrated to be legitimate. In these circumstances, we consider that the Jury should have been given simply the random occurrence ratio produced by the single locus probe tests and the blood group, though they could have been told that the result of the multi locus probe test increased that ratio to an indeterminate extent.

There was further debate between the experts as to the validity of the figure of 1 in 6,900 calculated by Mr Davie as the random occurrence ratio of the combined single locus probe results. That turned on a comparison of different approaches to applying the data contained in the population data base used to calculate the results of the tests. Happily we do not have to attempt to resolve this issue, for it is not sufficiently significant to affect the result of this appeal.

The relevant position is this. If one excludes from the calculation the result of the multi locus probe test, in a population base of 800,000 suggested as constituting those within a reasonable proximity of the scene of the crime, there may well have been 20 or so individuals with the same DNA profile as the Appellant and as the crime stain. This figure still renders it an extremely unlikely coincidence that both the Appellant and another of this small cohort should have been in the vicinity of the crime at about the time that it was committed, the more so when one postulates that this other individual would also have had to share with the Appellant the other attributes - general appearance, age and local accent - that the complainant described in her assailant. Nonetheless we do not feel that we can say with confidence that these considerations demonstrate that the Appellant was rightly convicted, however compelling his evidence and that of his alibi witnesses may have been. Our doubts are augmented by the discovery of pubic hairs which had originated neither from the Appellant nor from the complainant. For these reasons we have concluded that the conviction is unsafe and must be quashed.

Having regard to the strength of the case against the Appellant we would normally be minded to order a retrial. We have, however, been persuaded that in the circumstances of this case that course would not be appropriate. These are:

1) The Appellant has already served over half of his sentence and is eligible for parole.

2) A retrial would involve balancing the Appellant's alibi evidence, and his own testimony, against the DNA results. Time will not have altered the impact of the latter, but the Appellant would inevitably be at a disadvantage in seeking to establish his account of his movements at the material time.

This is not a case where allowing the appeal carries the implication that there has been a miscarriage of justice, but for the reasons we have given we shall accede to the submission made on behalf of the Appellant that there shall be no retrial.

GARY ADAMS

On the 27th March 1991 in the Crown Court at Stafford the Appellant was convicted of buggery contrary to Section 12(1) of the Sexual Offences Act 1956. He was sentenced to 5 years imprisonment - a sentence which he has now served. He appeals against conviction by leave of the Single Judge, who granted an extension of time of some 3 years 8 months.

The Facts

The events which gave rise to the charge against the Appellant occurred on October 4th 1989. The complainant, who was then aged 32 or thereabouts, was a divorced woman who lived on her own at S Street, Newcastle in Staffordshire. She was psychologically disturbed and had formed the habit of phoning the Samaritans for comfort and assistance. Sometimes, when she was very distressed, members of the Samaritans would visit her. This they always did in pairs, for that was one of the rules of the organisation. On the evening of October 4th the complainant telephoned the Samaritans. She spoke to a man who said his name was Gary. This was the Appellant, who worked at the Samaritans as a volunteer. The complainant asked if there was a woman she could speak to and the Appellant answered that there was not. Thus far the facts are common ground, but no further.

The Complainant's Evidence

The complainant said that she told Gary that she was very distressed. He said she sounded as though she needed a hug and she agreed. He then asked if she would like someone to come round. She answered that he could not come on his own and that there should be a woman present. About 10 or 15 minutes later a man arrived on his own. His voice was that of the man to whom she had spoken on the phone. He was wearing a dark grey, three quarters length coat made of grey, herring bone cloth, with large lapels, Farrah-type trousers and a woollen sweater. He took off his coat, hugged her and said "there I told you you needed a hug". She then became aware that he was sexually aroused, for he rubbed his erect penis against her. He put her hand in between his legs, he touched her breasts and then he put her hand on his penis. He pulled her back on to the settee and then on to the floor. He had her kneeling and thrust his penis against her face, asking her to perform oral sex which she refused to do. He undid and took off her trousers and pants. She told him that she did not want him to do anything and that she was menstruating. He said, "There are other ways". He told her to kneel down on all fours. He penetrated her anus which caused her excruciating pain. After several thrusting movements he ejaculated and then he withdrew from her. He asked her for a tissue and he wiped himself with the tissue that she had provided and zipped up his trousers. He walked to the door and said, "Don't get up. I don't want to embarrass you any more", and then he left. The following day she went to work and at about mid-day she telephoned a friend, Joanna, and arranged to see her that evening. When they met she told Joanna what had happened but did not go into detail.

Joanna gave evidence. She said that the complainant said that she had been forced to have oral sex and then intercourse, which she assumed meant conventional sexual intercourse. On the 13th October the complainant went with Joanna to the Samaritans Centre where she made a complaint about the Appellant. A month later, on the 14th November, she phoned the Samaritans and found that she was talking to the Appellant. She realised that her complaint had not been acted upon. On the 20th November she went and told her story to the Police.

The Appellant's Evidence

The Appellant said that his phone call with the complainant on the night of the 4th October ended when she became abusive. He finished his session at the Samaritans at 10.35 pm and drove home, arriving at about 10.50 pm. He had with him a coat, such as that described by the complainant, but was not wearing Farrah trousers. He did, however, own a pair of such trousers. The allegations made against him were untrue. He was interviewed by the Police on the 29th November. The Appellant's mother and his girlfriend corroborated the timing of his arrival home on the 4th October.

Subsequent Events

On the 13th December the complainant signed a statement that she no longer wished to pursue the case and on the following day the Appellant was informed by the Police that he was 'in the clear'. However, in January 1990 the Police carried out a search of the complainant's home for forensic evidence. A chair cushion was found which bore traces of semen. The Appellant provided a blood sample and tests - to which we shall shortly refer in detail - showed a DNA match between this and the semen on the cushion. When told of this the Appellant suggested an explanation which was fanciful. In September 1989 he had provided a semen specimen for fertility analysis, which he deposited at the Central Pathology Laboratory. Perhaps the complainant had obtained this from the hospital where she worked in order to frame him.

The Forensic Evidence

Mr Webster, a forensic scientist, gave evidence at the trial of the match that he had found between the crime stain and the Appellant's blood sample. He had carried out four single locus probe tests which had resulted in eight matching bands. Calculations based on these, of the nature that we have described, produced a random occurrence ratio of the matching bands of 1 in 27 million. That is not, however, how Mr Webster described his results to the Jury. The material passage from his examination in chief was as follows:

"Q. Were you able to obtain a DNA profile from the blood samples?

A. Yes, I did.

Q. Did you compare it with the profile which you obtained from the semen?

A. Yes, and it was the same.

Q. Perhaps you could help us about this. The fact that the DNA profile is the same for the blood sample and for the semen stain, what does that show?

A. It shows that the semen could have come from the same individual who provided the blood sample.

Q. Is it possible that the semen could have come from a different person from the person who provided the blood sample?

A. It is possible but it is so unlikely as to really not be credible. I can calculate; I can estimate the chances of this semen having come from a man other than the provider of the blood sample. I can work out the chances as being less than 1 in 27 million.

Q. Is that what it comes to in this case?

A. That is what it comes to in this case.

Q. So, it is really a very high degree of probability indeed that the semen stain came from the same person who provided the blood sample?

A. Yes. You really have to consider the size of the group of individuals who could possibly be the source of this semen. Now, there probably are only 27 million male people in the whole of the United Kingdom so a figure of 1 in 27 million does tend to imply that it is extremely likely there is only really one man in the whole of the UK who has this DNA profile."

When summing up in relation to this evidence, the trial Judge said this (p.30 of the transcript):

"....it is difficult to over emphasise the importance of the forensic evidence in this case which, if it is right, puts his semen onto [the complainant's] cushion...

It does prove, the forensic evidence if you accept it, that his sperm is on her cushion.... That, you may think, is why it is almost impossible to over-emphasise the importance of the forensic evidence and what you may make of the results of that forensic evidence."

On the following page, the Judge added this:

"You heard the evidence of Mr Webster that in this case there were eight matching characteristics of DNA, eight matching characteristics. Of course, the probability goes up in a geometric progression and the more matching characteristics you find the graph climbs very steeply indeed. If you find one characteristic that does not match well that is that. It is not the same person but in this case he found eight characteristics. That means, on the evidence of Dr Webster if you accept it and there is nothing to contradict it, not less than 1 in 27 million people. That means, I should think, I do not know what the population of the United Kingdom is but I should not think there were more than 27 million males in the United Kingdom, which means that it is unique."

The First Ground of Appeal

The first ground of appeal contends that the way in which the DNA evidence was presented to the Jury was inappropriate and erroneous. Just as in the case of Doheny, there is force in the complaint that Mr Webster and the Judge propounded the Prosecutor's fallacy. But also, just as in the case of Doheny, this fallacy does not significantly alter the picture if the random occurrence ratio is as extreme as 1 in 27 million.

Professor Donnelly gave evidence for the Appellant in this case also. The best he could do was to point out that on that ratio there was a probability of about 26% that at least two men in the United Kingdom in addition to the Appellant had the same DNA profile as the crime stain. Mr Cooke for the Appellant sought, however, to persuade us that Mr Webster had failed to have regard to a number of factors, which significantly reduced the random occurrence ratio. A paper by Dr Balding, whom Mr Cooke had hoped to call as an expert witness, succeeded in reducing the ratio to 1 in 4 million. Professor Donnelly was not prepared to go quite as far as this, though he suggested a number of respects in which Mr Webster's calculations were over generous to the Prosecution.

We did not find this evidence impressive, for the Crown experts were able to point to aspects of Mr Webster's approach which were conservative and which tended to balance the points made by Professor Donnelly. But in our view none of these issues have any significance in the context of the Adams appeal. The complainant had, quite comprehensively, identified one man - the Appellant - as her assailant: the telephone call, his voice, his appearance, his clothing. When to this was added the fact that his DNA profile matched the crime stain, no Jury could be in doubt that he it was who left that stain, whether the statistics suggested that there existed one other man, or ten, or even a hundred in the United Kingdom with the same DNA profile. There is no merit in the first ground of appeal.

The Other Grounds of Appeal

A common theme underlies the other grounds of appeal. Although it has at all times been the Appellant's case that he never entered the complainant's home on the 4th October, the Judge should have directed the Jury to consider an alternative possibility: that the Appellant had gone to the complainant's home, that he had left the semen stain, but that he had done so in the course of some sexual activity other than buggery.

In our judgment a Judge is under no duty to put before the Jury the possibility of the existence of facts which are at odds both with the evidence adduced by the Prosecution and the evidence adduced by the Defence, unless there is good reason for believing that those facts may represent what occurred. Mr Cooke urged that such was the situation here. He made the following points:

•    No blood was found by Mr Webster on the cushion.

•    No injury was found to the anus when the complainant was medically examined.

•    When the complainant described what had happened to her friend Joanna she spoke of having been forced to submit to oral sex and intercourse, rather than buggery.

We do not accept that these points amounted to a case of alternative sexual activity involving the Appellant that should have been advanced by the Judge to the Jury. Mr Webster was asked about blood and he said that he did not test for this. The semen stains he found were not visible stains and he certainly could not be categoric that there was no blood there. The complainant was not medically examined until the 13th October, when she consulted a doctor because of apprehension that she might have been infected. The Judge remarked to the Jury that by then it was far too late for any medical signs.

As for what the complainant told Joanna, we do not find what she said manifestly inconsistent with the complainant's account of having the Appellant thrust his penis into her face, followed by an act of buggery.

Had the semen stain not been found, so that the case for the Crown turned essentially on the evidence of the complainant alone, we do not see how it could properly have been suggested that the Judge should have invited the Jury to consider an alternative factual scenario - namely that the Appellant had visited the complainant and indulged in sexual activity short of buggery. The issue would have been simply whether the Jury accepted the complainant's story, in all its aspects, or not. The semen stain strongly corroborated the complainant's evidence that the Appellant had visited her on October 4th. It was entirely consistent with her evidence that the Appellant buggered her, although also consistent with other types of sexual activity. We cannot see that the fact that the Prosecution case included the semen stain and the DNA evidence required the Judge to advance what would have been a fanciful and speculative case for the Jury's consideration - cf Johnson [1994] CLR 376.

For these reasons we reject the submission that the Judge should have invited the Jury to consider an alternative sexual scenario for which the evidence provided no support at all.

Ground 2. Corroboration

Mr Cooke has submitted that the Judge misdirected the Jury on the evidence that was capable of corroborating the complainant's evidence. The Judge gave the Jury a particularly strong direction on the dangers of convicting in the absence of corroboration. He then said:

"I will straightaway tell you that in this case the one piece of evidence which is capable of being corroboration is the defendant's semen stain, if you find it to be the defendant's, on [the complainant's] cushion. That evidence is capable of being corroboration because, of course, it shows sexual activity, as taking place in her room, sexual activity involving the defendant. If you find it is his semen, then that evidence is capable of amounting to corroboration."

It is Mr Cooke's submission that this direction was defective because the semen stain, while potentially corroborative of the complainant's evidence that the Appellant had visited her on October 4th and indulged in sexual activity, did not corroborate her evidence that this activity amounted to buggery. In support of this submission Mr Cooke referred us to West [1993] CLR 860 and to Ensor (1989) 89 Cr.App.R.139. These decisions supported the proposition that where the elements of a sexual offence are in issue, the Judge should direct the Jury as to the desirability of corroboration of each element.

The automatic requirement to give a corroboration direction in the case of a sexual offence has been abolished by S.32 of the Criminal Justice and Public Order Act 1994. This recognises the fact that such a direction is not necessary or desirable in the case of every sexual offence. The corollary of this is that a guilty verdict in respect of a sexual offence will not necessarily be unsafe where no such direction has been given. Whether a corroboration direction is desirable will depend upon the facts of the individual case - see Makanjuola [1995] 2 Cr.App.R. 469.

In the present case, having regard to the disturbed personality of the complainant, we consider that it was desirable that a corroboration direction should have been given. We do not, however, consider that the Judge should have directed that it was desirable that there should be corroboration of every element of the complainant's evidence.

Even before 1994 this Court held that corroboration that went to the heart of the dispute - namely whether or not the complainant had consented to whatever the Defendant was doing - sufficed to remove the danger of convicting on the evidence of the complainant alone:

"Where there is corroborative evidence going to the heart of the dispute it would be unreal nevertheless solemnly to warn the Jury that, because the case involved a sexual complaint, there still remained a particular danger of convicting the accused without some additional confirmatory evidence, without some corroboration of the further element necessary to establish attempted rape rather than indecent assault or to establish either count rather than a completely non- sexual assault" -

R v Bailey [1993] CLR 860 at 861. We think those words apply aptly to the present case. Before the Judge summed up he discussed with Counsel what he should say about corroboration. Counsel for the Crown submitted:

"One has to look at what the issue is.... if the defendant's case was that there had been some sexual activity but falling short of buggery, then obviously the fact of the semen stain itself would not be corroboration, but in the context of this case it plainly is...."

Later in the discussion the Judge responded:

"....really the central piece of evidence capable of amounting to corroboration is, as you say, the finding of the semen stain which is, on the evidence, unquestionably his, which therefore shows sexual activity involving him."

In our judgment, this exchange identified evidence which, if accepted, strongly corroborated the complaint in respect of most of the complainant's evidence and, in particular, the central issue of whether the Appellant visited her and indulged in sexual activity. The Judge more than once emphasised to the Jury that the presence of the semen stains did not prove that buggery had taken place.

When we strip away the technicalities of the old law and ask the question - is this conviction unsafe because the Judge did not give a fuller direction on corroboration? - our answer is an emphatic No.

Ground 3. Recent Complaint

In his grounds of appeal Mr Cooke questioned whether the evidence of the complainant's friend Joanna should have been admitted as a recent complaint. Before us he argued that the Judge should have drawn the Jury's attention to the fact that this evidence was possibly inconsistent with the complainant's evidence that she had been buggered. We have already stated that we are not persuaded that there was any inconsistency. We are also satisfied that this evidence was properly admitted as a recent complaint. There is nothing in this ground of appeal.

Ground 4. Alibi

Mr Cooke contended that, when dealing with the Appellant's alibi, the Judge should have given a direction that there was no burden on the Appellant to establish his alibi. The burden was on the Crown to disprove it. At the beginning of what was a relatively short summing up, the Judge said:

"The burden of proving the case rests upon the Prosecution. It is not up to the Defendant to prove anything to you and you must not fall into the trap of thinking that because he has given evidence - and he is not obliged to do so - and because he has called witnesses that means that in some way he has to prove something. He does not. It is entirely up to him whether he gives evidence or not and calls witnesses or not. He does not have to prove a thing to you."

In the light of this direction, no additional direction was required in relation to the Appellant's alibi. Nor, having regard to the strength of the DNA evidence, could any shortcomings in this respect have put in doubt the safety of the verdict.

Ground 5. Lies

Mr Cooke contended that the Judge should have given the Jury a Lucas direction [(1981) 73 Cr.App.R.159] in relation to a possible finding by the Jury that he had lied about his alibi and about not being responsible for the semen stain. To those conditioned by the spate of recent authorities in relation to lies - which significantly post dated his summing up - the Judge's direction on lies looks stark indeed. At p.30 he said:

"... if you accept that his sperm is on her cushion you may think that he has told the Police a pack of lies about never having been there and, Members of the Jury, unless you think his account of how his sperm got on her cushion may reasonably be true then he has told you a pack of lies, has he not? That is a fact. That, you may think, is why it is almost impossible to over-emphasise the importance of the forensic evidence and what you make of the results of that forensic evidence."

At p.31 he added:

"... if you think it is really just fantasy if you think that then it means he has lied to the Police and lied to you. It is then up to you to decide what conclusion you draw from that but it is right to remind you, and I do, that the presence of semen does not itself prove buggery."

The lies to which the Judge referred were, in effect, variations on the theme that the Defendant did not go to the complainant's home on the 4th October. Had there been any conceivable motive for telling such lies other than an attempt untruthfully to persuade the Jury that he was not at the scene of the crime, a Lucas direction should have been given. Mr Cooke did not suggest that this was the case. His submission was that all the Appellant's evidence about the central issue - his visit to the Appellant's home - could have been false not because of his desire to avoid rightful conviction for buggery but because he did not wish it to be known that he had broken all the Samaritan rules by calling alone on someone who had sought comfort and indulging in sexual activity - but not buggery - with her. It seems to us that this submission turns on the question of whether the Judge was required to put before the Jury the possibility that the Appellant called on the complainant and indulged in sexual activity other than buggery. We have already ruled that no such requirement existed. We would add that if such a scenario had occurred, it would have been extraordinary if the Appellant had not decided to tell the truth about it once DNA evidence was advanced which he would have understood - and rightly understood - gave the most cogent support to the complainant's evidence that he had called on her on the 4th October.

This ground of appeal is no more successful than the previous grounds in persuading us that the Appellant's conviction was unsafe.

For these reasons this appeal will be dismissed.