Neutral Citation Number: [2009] EWCA Crim 1876
Case No: 200801604 D4  200801607 D4
IN THE COURT OF APPEAL (CRIMINAL DIVISION)
ON APPEAL FROM THE CENTRAL CRIMINAL COURT
His Honour Judge Kramer QC

Royal Courts of Justice
Strand, London, WC2A 2LL

Date: 02/10/2009
Before :

LORD JUSTICE HUGHES
MRS JUSTICE RAFFERTY
and
MRS JUSTICE SLADE
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Between :

	Dean Atkins and Michael Atkins	Appellants	
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	The Queen	Respondent	

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Mr J Stone and Mr P Woodall (instructed by Ally Lindsy) for the Appellants
Mr J N Donne QC and Mr J Evans  (instructed by Crown Prosecution Service) for the Crown

Hearing date : Thursday 30th July 2009
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Judgment
Lord Justice Hughes : 
1.	The issue in these appeals relates to the permissible manner in which an expert in facial photograph comparison (often called ‘facial mapping’) may express his conclusions. The expert gave evidence about the similarities between the face of the offender caught on indistinct CCTV footage and the face of Dean Atkins. There is and was no suggestion by the Crown or the expert that he could positively identify Dean Atkins.  There is and was no argument by the defence against the admissibility of the expert’s evidence as to similarities between the face on the camera and that of Dean Atkins.  What is contended is that it was impermissible for the expert to say that in his view those similarities lent something between support and strong support to the allegation that the man in the camera shot was Dean Atkins.  The expert habitually used, and used on this occasion, what has been described as a sliding scale of propositions running from “lends no support” to “lends powerful support”.  It is contended that such an expert should never use any of these expressions but should be confined to identifying the similarities or dissimilarities between the faces compared.
2.	On the night of Sunday 5th/Monday 6th November 2006 a team of three men committed two armed robberies at the homes of targeted victims in the Uxbridge/Yiewsley area of west London.  Both offences had clearly been planned.  The first target was a Chinese widow in her sixties who lived alone and might be expected to have at home the takings from the family restaurant.  The second was the occupier of a substantial house who might be expected to have valuables in his home. There was ample evidence that the offending team was the same for each, and that it moved more or less immediately from the first house to the second.  The Chinese lady had been attacked, dragged around her house bleeding, apparently in search of a safe, and eventually bludgeoned to death.  The robbers had then driven about 2 or 3 miles to the second target house.  There they forced entry, terrorised the occupier and his two teenage children with an ‘imitation’ pistol, a knuckleduster and a knife, but were, in the end, repulsed.  They left, leaving the gun behind. There were accordingly counts for murder, two aggravated burglaries, wounding the second homeowner with intent, and for a firearms offence.  The appellants were convicted by the jury on all counts.
3.	By the time of the trial it was common ground that one of the robbers was a man called Carty, who had been arrested but had killed himself whilst on remand.  These two appellants, who are brothers, were agreed to have been in Carty’s company not long before the offences.  Dean had escaped from prison in Kent on the previous day (Saturday), and had been helped to do so by Michael and Carty.  The three had been together in a local public house on the evening of the robberies.  They were also found together the following morning at about 11 a.m. at the home of a girlfriend of Carty, who thought that they had slept that night in her house. There was also evidence that about ten days later the three of them had been together in the same public house when Michael Atkins produced a ring answering the description of one specially made for the Chinese family and made a joking reference to it having been made easy for him.   But it was the case of both these appellants that they had had nothing to do with the robberies, which had been committed by Carty in the company of others who had never been found.  By their defence statements each advanced an alibi for the night in question.  Dean contended that he was at the home of his sister and went to the house of Carty’s girlfriend only the next morning.  He did not give or call evidence at the trial.  Michael contended that he had spent the night in bed with Carty’s girlfriend, and gave evidence to that effect;  she and her mother both said that he had not. 
4.	At the house of the second robbery there was a CCTV camera outside, covering the front door.  The three robbers wore balaclava masks, but the camera showed that at one stage one of them came to the doorway and looked out, not then wearing the mask. It was this footage which was examined by Mr Neave, an expert in facial comparison. 
5.	Mr Neave is a medical artist of over 40 years’ experience in service at the University of Manchester.  His speciality is in facial features and their relationship to the underlying anatomy.  For about 20 years he has specialised also in facial comparison.  His report, and in due course his evidence, explained his approach and techniques as follows:
i)	it is well known that a number of persons may share the same proportions of face, and similar features;  two people may have faces which appear indistinguishable to his examination;  accordingly his comparison cannot make a positive identification, although it may make a definite exclusion because there may be irreconcilable differences in features;
ii)	he uses a computer with high definition to compare images;  the CCTV footage is examined stopping every second;
iii)	two faces being studied are (a) compared for their horizontal and vertical proportions, (b) compared by examination and description of the shape and form of their features (this known as morphological examination), and (c) may be measured for both distances and angles between features, using a grid superimposed on the faces. The first and third exercises require comparable camera angles and perspective;  the second does not, but any difference in perspective must be allowed for.
iv)	if those tests do not eliminate the suspect, the photographs can also be superimposed one on the other, and part of one face can be substituted for the same part of the other, and juxtaposed with the remainder of the other, both as further checks.
6.	Mr Neave had examined the CCTV shot, which was far from clear to the naked eye.  He had compared it with photographs of both appellants, Carty, and approximately 20 other men who were known burglars in the Uxbridge area.  That last collection was not of course a comprehensive range of possible culprits but no doubt provided a range of facial features.  The exercise had taken two weeks, and some 16 hours had been spent concentrating on the comparison with the photograph of Dean Atkins.  He had eliminated Carty and Michael Atkins by the second (morphological) stage, the first easily and the second after more subtle examination.  He explained why by reference to comparison prints and to their noses, jaws, earlobes and the like.  He also eliminated the other 20 men.  In relation to Dean Atkins he said that he could find no difference between the photograph of Dean Atkins and the CCTV image on morphological examination and identified particular similarities in eight different areas, of which the principal were nose, mouth, upper lip and chin.  The camera angles from which the photograph and the CCTV image were taken were virtually identical and thus sufficient to enable grid measurements to be made. These were also consistent with the photograph of Dean, and so was the product of the two superimposition or substitution tests. 
7.	In evidence before the jury Mr Neave identified nine different factors which could affect the reliability of his exercise.  Many related to the quality of the photographs and the various things which could affect that.  Another was pixilation, which is or can be image compression when a photograph is transferred to a computer.  Two more of his stated risk factors were:
i)	the possibility that two different people may appear indistinguishable; and
ii)	the fact that there exists no database of facial characteristics.
He also dealt with the particular quality of the CCTV photograph of the offender, which was significantly limited by short duration, some element of distortion at one edge, shadow and the sudden change from dark to light when the door was opened and the person appeared with light to one side beyond him.  
8.	Having traversed the detail of consistent features and absence of any inconsistencies, and having explained his techniques, Mr Neave expressed his conclusions by reference to a range of expressions.  They were set out in his written report in tabular form as follows:
Level	Description	
0	Lends no support	
1	Lends limited support	
2	Lends moderate support	
3	Lends support	
4	Lends strong support	
5	Lends powerful support	
Mr Neave told the jury that he used these five different forms of expression.  In the present case, he said that in his opinion the similarities which he had identified gave support to the proposition that the man on the camera was Dean Atkins which he put somewhere between “the top of (3) and into (4).”  This part of his evidence, as summarised by the judge, was in these terms:
“This comparison therefore offers a level of support for the allegation that Dean Atkins and the offender are one and the same person, between ‘it lends support’ and ‘lends strong support’ to that conclusion.  But you should remember this, that, as Mr Neave conceded, there is no database which would enable him to give a statistical analysis and so his scale is based on his own experience and expertise and, he added, in this case on the fact that he was able to exclude a large number of people, including one who was very similar to Dean Atkins, his brother Michael.”
9.	The judge was asked to rule this aspect of Mr Neave’s evidence inadmissible.  He was not asked to exclude the remainder of his evidence, making and explaining the comparison between the faces and identifying the similarities.  Mr Neave’s expertise in his field was accepted.  This case therefore does not raise any question as to the judge’s power at common law to exclude evidence tendered as expert, if it be argued that the expert is insufficiently qualified or that his evidence is insufficiently based upon expertise.  We say no more about that than that there can be no doubt that such a power exists.  That is because he who asserts admissibility must demonstrate it.  Evidence of opinion is not ordinarily admissible.  Opinion based upon identifiable expertise outside the experience of the jury is one exception.  If objection be taken to admissibility (though not otherwise) it must be determined by the judge.  It is for him who tenders such evidence to establish the exception, viz the expertise and that it is the foundation of the opinion.  The power to rule on admissibility applies equally to Crown and defence.  It does not derive from section 78 Police and Criminal Evidence Act (although that may additionally be relevant in some cases).  
10.	The partial objection made in this case to the opinion of Mr Neave was based upon this undoubted jurisdiction in the judge.  Mr Stone’s careful submission accepted that the expertise of Mr Neave properly extended to his techniques, to his informed examination and comparison of facial features and to the demonstration of similarities or dissimilarities.  Nevertheless, he contends, the absence of any database cataloguing the numbers of person with particular facial features or measurements meant that there was no expertise-based justification for his expression of the level of support which that comparison gave to the allegation that the man in the photograph was Dean Atkins.
11.	That contention was based by Mr Stone upon both principle and authority.  As to principle, he submits that the use of the expressions of level of support in the form of an ascending scale carries the risk of bestowing upon evidence which is purely subjective a spurious scientific authority.  It may, he says, mislead the jury by suggesting to it that there is an arithmetical scale or statistical basis for the strength of the comparison.  Furthermore, he says, although Mr Neave made it clear that he could not, by his techniques, identify Dean Atkins as the man in the photograph, the use of his expression ‘lends some to strong support’ came perilously close to identification, and was likely to be over-valued by the jury.  
12.	Mr Stone relied heavily on some observations of Mitting J, giving the judgment of this court in the unreported case of R v Gray [2003] EWCA Crim 1001, at paragraph 16:
“We do not however wish to pass from this appeal without making general observations about the use of facial imaging and mapping expert evidence of a reliable kind. Mr Harrow, like some other facial imaging and mapping experts, said that comparison of the facial characteristics provided ‘strong support for the identification of the robber as the appellant’.  No evidence was led of the number of occasions on which any of the six facial characteristics identified by him as ‘the more unusual and thus individual’ were present in the general population, nor as to the frequency of the occurrence in the general population of combinations of these or any other facial characteristics.  Mr Harrow did not suggest that there was any national database of facial characteristics or any accepted mathematical formula, as in the case of fingerprint comparison, from which conclusions as to the probability of occurrence of particular facial characteristics of combinations of facial characteristics could safely be drawn.  This court is not aware of the existence of any such database or agreed formula.  In their absence any estimate of probabilities and any expression of the degree of support provided…..must be only the subjective opinion of the facial imaging or mapping witness.  There is no means of determining objectively whether or not such an opinion is justified.  Consequently, unless and until a national database or agreed formula or some other such objective measure is established, this court doubts whether such opinions should ever be expressed by facial imaging or mapping witnesses.  The evidence of such witnesses, including opinion evidence, is of course both admissible and frequently of value to demonstrate to a jury with if necessary enhancement techniques afforded by specialist equipment, particular facial characteristics or combinations of such characteristics so as to permit the jury to reach its own conclusion….but on the state of the evidence in this case, and if this court’s understanding of the current position is correct in other cases too, such evidence should stop there.”
13.	There are several cases in which the general admissibility of photo-comparison or facial comparison/mapping evidence has been ruled admissible by this court without consideration of the limitation now suggested by Mr Stone:  they include Clarke [1995] 2 Cr App R 425 and Briddick [2001] EWCA Crim 984.  Their effect was authoritatively summarised in the judgment of Rose LJ in Attorney-General’s Reference 2 of 2002 [2003] 1 Cr App R 321, although in that case the court was concerned with non-expert evidence of recognition from camera footage.  This court recognised that a suitably qualified expert with facial mapping skills may properly give opinion evidence of his comparison of images from the scene, enhanced or otherwise, and a reasonably contemporary photograph of the accused.  The images should be available for the jury. This last-mentioned case was before the court in Gray.   
14.	Other decisions bearing on Mr Stone’s submission were, however, clearly not before the court in Gray. There is no indication that the court was referred R v Stockwell (1993) 97 Cr App R 260.  In Stockwell Lord Taylor CJ (with Henry and Blofeld JJ) had confronted the admissibility of evidence of facial comparison (as it happens given by the same Mr Neave whose evidence is in question before us).  Two submissions had been made, both of which this court rejected.  The first was that Mr Neave was not an expert, having “no scientific qualification, no specific training, no professional body and no database.” (see p 264;  our emphasis).  The second was that in any event he should not have been permitted to give evidence on the very issue before the jury, in the form of the expression: “There is limited information but I think the exhibits reveal that there is support for the view that the robber and the suspect are the same man on count 2, but it is not anything like as strong as the support on count 1.”  The rejection of this second submission was chiefly couched, as plainly the argument had been, in terms of what used sometimes to be described as the ‘ultimate issue’ question, viz: is there a rule that the witness cannot give his opinion on the very question the jury must answer ?  (There is not:  consider for example insanity and see Cross and Tapper on Evidence, 11th ed p 574).  But the submission raised exactly the issue now addressed, and it was rejected in these terms:
“But since counsel can bring the witness so close to opining on the ultimate issue that the inference as to his view is obvious, the rule can only be….a matter of form rather than substance.
In our view an expert is called to give his opinion and he should be allowed to do so.”
15.	In Hookway (unreported 1 February 1998;  9803369/Y3) Rose LJ, giving the judgment of this court, held that a case which depended entirely on evidence of facial mapping was properly left to the jury.  The witness (again Mr Neave) had expressed his conclusion by saying that the similarities found did not identify the accused but provided “very powerful support” for the proposition that he was the offender.  The argument was not that the evidence was inadmissible but that in the absence of a database it could not by itself give rise to a case to answer.  The point now at issue was therefore not taken in the form which Mr Stone now gives it, but the case is a further example of evidence of this kind being explained to the jury by use of an expression of the level of support given.  Moreover the absence of a database was at the centre of the appeal, which this court dismissed.  Unsurprisingly, since the case is unreported, it cannot have been before the court in Gray.
16.	What the court was dealing with in Gray was an expert who over-stepped the mark and whose reliability had subsequently appeared seriously questionable.  His findings as to the height of the photographed person had been directly refuted at trial by another comparison expert.  After the trial in question, his evidence in two other cases had been proved wrong and this court had expressed doubts about his evidence.  In consequence, the CPS had advised that he ought no longer to be instructed for the Crown and it was conceded on appeal that he would not have been called if these things had been known at the time of the trial.  The actual decision of this court in Gray was thus limited to a ruling that the conviction was unsafe given the serious doubt about the witness whose evidence had been relied upon.  We entirely understand the proper caution about facial mapping evidence generally, articulated by Mitting J in Gray; the absence of a database is in particular a matter which must be explained unequivocally to any jury considering such evidence.  But the question whether such an expert can give his opinion in the terms used in this present case did not arise in Gray and was not argued.  As a result, the cases we have set out were not before the court.  If they had been, we doubt that the court would have expressed itself in the terms we have quoted.
17.	In contradistinction to Gray, in R v Gardner [2004] EWCA Crim 1639, this court not only affirmed the general admissibility of expert facial comparison evidence, but held (at paragraph 43):
“There is no rule…that in a case such as the present an expert witness cannot go further than saying ‘there are the following similarities’ leaving the ultimate decision to the jury, as opposed to the expert witness actually giving a view as to the degree of probability of the images being the same.”
That was said after consideration of the passage in Gray which we have previously quoted.  The court said that Gray had sounded a ‘note of caution in relation to new techniques relating to identification.’  It emphasised the need for such caution, and for judicial warning.  In that case the trial judge, Sir Edwin Jowitt, had expressly warned the jury that it could not test the results of the expert’s examination in the way in which an examiner can test a student’s paper in mathematics and so it should approach the evidence with caution, remembering also that an honest witness can appear very persuasive but may yet be mistaken.  But this court upheld the admission of the opinion of the expert in that case that ‘there was a high degree of probability’ that the person in the photographs was the same as in the admitted photographs of the defendant.  In doing so it referred to the several decisions of this court establishing the general admissibility of facial comparison evidence, and to the clear law that expert opinion  evidence may be given by reference to studies which the expert has done but which a jury does not see.  
18.	It follows that as a matter of precedent, Gardner is a decision, after argument, precisely on the point now before us.  Gray is a powerful expression of opinion, obiter, without the benefit of argument, and without citation of all relevant authority.  
19.	Mr Stone also relied on the judgment of Spigelman CJ in the New South Wales case of R v Tang [2006] NSWCCA 167, where there is a helpful discussion of photographic comparison evidence in the context of one particular expert.  The relevant local law was contained in s 79 Evidence Act 1995 (NSW), which provides that expert opinion evidence is admissible if the witness has specialised knowledge based upon training study or experience and the opinion is wholly or substantially based on that knowledge.  There is no such statutory provision in English law, but the common law is as we have set out in paragraph 9 above.  
20.	In that case the court was considering the evidence of photographic comparison both of facial features and posture.  In the course of the judgment, the court described the use of a similar sliding scale of expressions, as employed here by Mr Neave, as having no scientific basis and as being ‘no more than a series of convenient labels, arranged in an ascending hierarchy, that state a conclusion’ (see paragraph 88).  Later, in arriving at the court’s conclusion, the Chief Justice said (at paragraph 154) that this was one of three parts of the expert’s evidence which did not go beyond mere ipse dixit. The court also cited with approval the passage from Gray which we have quoted above.  Says Mr Stone, that demonstrates that in Tang the court was holding that the use of the sliding scale of expressions is not admissible because not sufficiently based on specialised knowledge.
21.	In fact, however, the court in Tang did not have to grapple with the admissibility of the use of a sliding scale of expressions of conclusion about admissible evidence of facial comparison.  The expert’s evidence of facial comparison methods and of similarities revealed was agreed upon all sides to be admissible.  What led to the decision that part of her evidence should have been excluded was that she had unilaterally extended the comparison from facial comparison to body posture, had asserted that the posture alone of the defendant was a ‘unique identifier’ when there was no evidence of any body of knowledge identified to justify such a proposition, and had based herself solely on a ‘protocol’ of her own devising, which she declined to reveal on the grounds that it was unique to herself and she wished to patent it.  That last feature of her evidence was described as ‘the critical matter’ (paragraph 154). It followed that this part of her evidence (unlike the facial comparison) failed the statutory test: there was simply no evidence of any body of specialised knowledge. (We observe that by contrast there seems to have been some such evidence in relation to posture comparison in the English case of Ciantar [2005] EWCA Crim 3559, although the decision did not turn upon it.) Moreover, unlike Mr Neave in the present case, she had purported positively to identify the accused from her comparison; that is something which responsible facial comparison experts recognise to be impossible, at least in the absence of some wholly individual feature, such as a birthmark. The court agreed, holding that although the facial comparison (but not body posture comparison) evidence was admissible to show similarities, it could not justify identification.   We might add that there were other flaws apparent in her evidence.  Her oral evidence was inconsistent with previously expressed opinion in her two written reports, which had spoken respectively of ‘limited support’ and ‘lends support’ (those two themselves also inconsistent with each other).  The manner of her expression of opinion in oral evidence was confused to say the least (see paragraph 33).  The court also took the view that a challenge could well have been made to her identification of two co-accused who had pleaded guilty, on the grounds that its introduction was unfair as against the third defendant, but such challenge had never been attempted.
22.	The observations about the sliding scale at paragraph 88 were accurate;  it does not have a scientific basis, in the sense of an arithmetical or numerical scale;  it is simply a convenient means of expressing a conclusion.  That does not, however, answer the question whether such a manner of expression is permissible.  That it was not permitted in relation to posture analysis in the particular circumstances of Tang leaves the question open in relation to facial comparison evidence which is agreed to be admissible.   Whether or not in New South Wales photograph comparison experts are currently permitted to use such expressions in relation to evidence agreed to be admissible is not clear; the same witness was confined by the Crown to listing similarities in the trial of Jung [2006] NSWSC 658, but that may have been out of understandable caution.    
23.	On principle, we accept the caution with which any expression of conclusion in relation to evidence of this kind (and others) needs to be approached.  We agree that the fact that a conclusion is not based upon a statistical database recording the incidence of the features compared as they appear in the population at large needs to be made crystal clear to the jury.  But we do not agree that the absence of such a database means that no opinion can be expressed by the witness beyond rehearsing his examination of the photographs.  An expert who spends years studying this kind of comparison can properly form a judgment as to the significance of what he has found in any particular case.  It is a judgment based on his experience.  A jury is entitled to be informed of his assessment.  The alternative, of simply leaving the jury to make up its own mind about the similarities and dissimilarities, with no assistance at all about their significance, would be to give the jury raw material with no means of evaluating it.  It would be as likely to result in over-valuation of the evidence as under-valuation.  It would be more, not less, likely to result in an unsafe conclusion than providing the jury with the expert’s opinion, properly debated through cross-examination and, if not shared by another expert, countered by contrary evidence. 
24.	That approach is supported by the decision of this court in Luttrell [2004] EWCA Crim 1344,  [2004] 2 Cr App R 31 in connection with expert evidence of lip-reading.  The court rejected the submission that such evidence could not be admissible because it had not been demonstrated to be verifiable in scientific terms.  Rose LJ said this (at paragraph 34):
“A skill or expertise can be recognised and respected and thus satisfy the conditions for admissible expert evidence, although the discipline is not susceptible to this sort of scientific discipline.”
25.	If the informed expert opinion of the witness is inadmissible, then it must be inadmissible in the hands of both parties.  It would follow that a party affected by evidence of similarities could not adduce from the expert his opinion that the similarities in question did not, to the expert, mean very much:  for example that he would express himself no higher than that they ‘lend very limited support’ to the suggestion that the person in the photograph is who he is alleged to be.  That would be significantly to diminish the power of a party challenging evidence of this kind to explore and test it.  In this case the expert was called by the Crown, and that will probably more often be the case than that a defendant will rely on such evidence.  But that is not exclusively so.  In the aftermath of a multi-party incident inside or outside a nightclub, for example, it may be in the interests of one defendant to establish that a person caught on camera is not only not him, but has identifiable similarities with another known person, whether a co-defendant or a Crown witness.  
26.	That conclusion is consistent with the practice of experts in a number of fields to use this kind of scale of expressions of opinion.  Such expressions are commonly encountered, as counsel on both sides confirmed and our own experience suggests, in many other fields of comparison.  Some random examples are comparisons of handwriting or fibres, glass fragments or footwear patterns.  In some of those there is some, often very incomplete, data about the incidence of general occurrence;  in others there is no database.  
27.	We accept that there can be proper anxiety about new areas of expertise. Courts need to be scrupulous to ensure that evidence proffered as expert, for any party, is indeed based upon specialised experience, knowledge or study.  Mere self-certification, without demonstration of study, method and expertise, is by itself not sufficient. It sometimes happens that such anxieties are reinforced when experts overstate their case, as the experts under consideration in both Gray and Tang appear to have done.  But the remedy is not to prevent all experts, good and bad, from expressing any informed opinion at all as to the import of their findings.  The three principal remedies are (i) to have such evidence examined and, if appropriate, criticised by an expert of equal experience and skill, (ii) to subject the evidence to rigorous testing in the witness box and (iii) to ensure careful judicial exposition to the jury of the difference between factual examination/comparison or arithmetical measure on the one hand and, on the other, a subjective, but informed, judgment of the significance of the findings.  
28.	Although there are not a great many, there are several experts in the field of photograph comparison, who operate independently of one another.  Such were, for example, called to give evidence for the defence in Clarke and Gardner, whilst in Hookway it is clear that the defendant had been advised by such an expert although he elected not to call him.  Three different such witnesses gave evidence to the jury in Ciantar as well as two in relation to posture.
29.	The absence of a statistical database is something which will undoubtedly be exposed in cross-examination.  The witness may expect to be asked to explain how, if no-one know how often ears or noses of the shape relied upon appear in the population at large, it is possible to say anything at all about the significance of the match; his answers may be satisfactory or unsatisfactory but will be there to be evaluated by the jury, which will have been reminded by the judge that any expert’s expression of opinion is that and no more and does not mean that he is necessarily right.  Similarly, the expert may be expected to be tested upon the extent to which he has not only looked for similarities, but has actively sought out dissimilarities.  Those are but the simplest of the questions which plainly need to be asked of anyone offering evidence of this kind.  Cross examination will also be informed by the fullest disclosure of his method, generally, and of his working notes in the particular case being tried.
30.	In the present case, the judge’s treatment of this evidence in summing up to the jury is agreed to have been meticulous and entirely fair if the disputed expression of opinion was admissible.  As well as setting out in detail the extent and limitations of the evidence of Mr Neave, he made it wholly clear that it (i) was incapable of constituting positive identification, whilst it could positively exclude, (ii) involved no unique identifying feature in this case, (iii) was not based upon any database which could give any statistical foundation for his expression of opinion and (iv) was therefore, as to opinion of significance, informed by experience but entirely subjective.  He also told the jury plainly that the decision whether to accept expert evidence was for it and it alone.  Without attempting to ordain a form of summing up which can fit every case, we observe that in some instances it may help the jury for the judge to explain that the forms of expression are labels applied by the witness to his opinion of the significance of his findings and different experts may not attach the same label to the same degree of comparability.
31.	We conclude that where a photographic comparison expert gives evidence, properly based upon study and experience, of similarities and/or dissimilarities between a questioned photograph and a known person (including a defendant) the expert is not disabled either by authority or principle from expressing his conclusion as to the significance of his findings, and that he may do so by use of conventional expressions, arranged in a hierarchy, such as those used by the witness in this case and set out in paragraph 8 above.  We think it preferable that the expressions should not be allocated numbers, as they were in the boxes used in the written report in this case, lest that run any small risk of leading the jury to think that they represent an established numerical, that is to say measurable, scale.  The expressions ought to remain simply what they are, namely forms of words used.  They need to be in an ascending order if they are to mean anything at all, and if a relatively firm opinion is to be contrasted with one which is not so firm.  They are, however, expressions of subjective opinion, and this must be made crystal clear to the jury charged with evaluating them. 
32.	These conclusions upon the issue of the expression of the expert evidence make it unnecessary to consider the other evidence which implicated these defendants in these offences.  We should say only that there was ample other evidence of their guilt.
Sentence
33.	The judge passed upon both defendants a sentence of life imprisonment with a specified minimum term of 35 years.  Each seeks leave to appeal against the length of the specified term.
34.	Dean Atkins was 25 at the time of the offences and his brother Michael 24.  Both had substantial previous convictions, chiefly for dishonesty and particularly for burglary.  Neither had been convicted previously of grave violence, although Dean had a conviction for aggravated burglary.  Both had served several custodial sentences.  Dean had served sentences of four years and three and a half years.  Michael had served a sentence of three years and nine months.  
35.	The statutory starting point for the specified term was 30 years;  this was a murder committed for gain and carrying a firearm:  see Criminal Justice Act 2003, Schedule 21 paragraph 5(2).  The murder of Mrs Chung was aggravated by significant planning of the offence, its commission against a vulnerable victim and a not inconsiderable amount of physical violence inflicted upon her to try to make her divulge the whereabouts of her safe, before the final fatal attack.  
36.	We can see no basis for the suggestion that either man ought to have been sentenced on the basis that he may have been outside the house at the time and convicted without proof of intention to kill.  Neither had given any evidence of that possibility.  All three had been equipped with masks.  All three had taken an active violent part in the immediately following attack on the second household.  It was a natural inference that they had invaded Mrs Chung’s home in similar manner and numbers.  It is rightly conceded that those inside her house had clearly had the intention to kill.  Nor, despite the terms of a (disputed) out of court admission by Michael suggesting that Carty had lost control, do we see any basis for saying that the judge was bound to sentence these two defendants on the basis that Carty, had he been alive to be tried, would have received a longer sentence than they.  
37.	Comparisons with other sentences imposed since the passing of the 2003 Act but in relation to offences committed before 4 April 2005 are not helpful, because such transitional cases are governed by a different statutory regime and starting points significantly lower, under the practice statements of the then Lords Chief Justice.  There can be no doubt whatever that the new statutory starting point of 30 years has effected a major uplift in sentencing for the most serious murders.  
38.	The reason, however, for the specified period of more than 30 years in this case is that the judge was passing sentence both for murder and for the extremely violent and grave attack on the second household.  Since he was passing a life sentence for the murder, he correctly reflected the totality of the defendants’ offences in the specified period:  see O’Brien [2006] EWCA Crim 1741.  There is and could be no challenge to the judge’s conclusion that the second aggravated burglary, associated with wounding with intent involving multiple knife wounds, would by itself have merited a sentence of imprisonment for public protection based upon a notional determinate sentence of 14 years.  In those circumstances there is nothing arguably wrong in principle or manifestly excessive in an overall specified period of 35 years, long as that is.  
Conclusion
39.	For the foregoing reasons, the appeals against conviction are dismissed and the applications for leave to appeal against sentence must be refused.