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Admissibility of Expert Evidence in Criminal Proceeding

The Admissibility of Expert Evidence in Criminal Proceedings


IntroductionPage 3

Philosophy of Expert EvidencePage 5

Section 1 - Opinion Evidence and Page 7

Its relationship to Expert Evidence

  1. Contradiction of Expert Evidence Law…………………………Page 11
  1. Ultimate Issue & Information in the Public Domain……………Page 13
  1. Peritus and Role of the Expert Witness…………………………Page 21
  1. Daubert & The Extent to which we utilise Expert Evidence……Page 29
  1. Conclusions……………………………………………………..Page 43

Section 2 - Hearsay & Its Page 48

Relationship to Expert Evidence.

Overall ConclusionsPage 54


Rabelais’ Judge Bridlegoose lays down a challenge for the legal profession. Bridlegoose threw dice to decide cases his deductive logic being that by using dice both sides had an equal chance of winning and therefore over the long run he would get the ‘right’ result in about half the cases[1]. A number that given the “arbitrary confusion, the obfuscation and chicaneries of lawyers and the possibilities of his own fallibility there was no such guarantee he would achieve this level[2]. All serious theoretical discourse on the Law of Evidence mandates ‘rectitude of decision[3] so the challenge is to get a better rectitude of decision in both design and practice than would be achieved by throwing dice. The scandals in recent years surrounding the cases of people such as Angela Canning[4] and Sally Clarke[5] and the overturning of convictions based on expert medical evidence have exemplified a classic example of a failure to get rectitude of decision; if their judgement had been based on the roll of a dice their results may have been fairer to them. The issue of expert evidence and its relationship to the exclusionary evidential rules on opinion and hearsay has been the subject of a large academic scrutiny and it is to this subject matter that this work will be focused upon.

The dangers of expert evidence are well rehearsed in the courts and it is a very contentious area, the well known dicta of Lawton LJ in the case of R v. Turner[6] exemplifies an ancillary point to the one made above, veracity is to be determined by the decision maker and we must become wary of abrogating such a right and stated that English law had to be wary of becoming too deferential or reliant on expert evidence because it is trial by judge and jury not by expert. The issues which this work seeks to deal with can be of the utmost importance, in this work I hope to critically assess the current state of the law as regards expert evidence post-Criminal Justice Act 2003[7]. The work attempts to fuse the two themes that I have implied here namely; the current attitude to expert evidence vis a vis the inherent conceptual dangers of the subject matter and secondly, whether as a whole it deals with the aims of the Law of Evidence more generally. Its position as an exception to such a large rule as Hearsay makes this Janus-like approach[8] necessary and lends considerably more conceptual clarity in a subject area which is contentious for various reasons with rich intellectual backgrounds.

We will start by looking at a history of the evolution of the concept of expert evidence as an exception to the exclusionary rule against opinion evidence which will combine both elements of practical law and theoretical background justifications for the existence of such laws. This section will be the bulk of the essay as we seek to build an in depth account of Expert Evidence and will look at a number of issues such as the courts attitude to new technologies and the detailed case law about the areas upon which the courts will allow expert evidence, always evaluating this against the background purposes of the rule. The evaluation in this section attempts to assess whether the rules on expert evidence exhibit a holistic coherence. This neatly flows into the second part of the work which will discuss expert evidence as an exception to the hearsay rule. In conclusion, I will draw both strands of the work together and propose a number of tentative amendments, however whilst this is a critical work, as we shall see the complicated nature of all the issues requires us to go into great detail about a large number of issues. The nature of this work is about criticising the lack of holistic treatment of the subject matter rather than substantive reforms.

Philosophy of Expert Evidence

The jurisprudential treatment of the law of evidence has a long history and it would be impossible in this section to do justice to the variety and complexity of the jurisprudential arguments that surround this subject matter. However as we shall see Expert Evidence is a particularly interesting subject because of its position in the Law of Evidence.

The general law of evidence in the Anglo-American system is built on a system of free proof with a number of exclusionary rules. This picture is very neat and easy for us to deal with on a conceptual basis. There is a clear need for any decision-maker to have all the available facts before him so that he can make the correct, or just, decision. However, some evidence is inherently misleading, unreliable and prejudicial. The individual rights of the parties and the demands of justice in the Anglo-American system mean that this evidence is excluded so that in effect the decision-maker makes his deliberations on all the ‘best evidence’ available at the time. The Adversarial trial system is the best way of eliciting this information from the available sources such as witnesses and real evidence. This is the prosaic understanding that underlies to a large degree the modern day criminal justice system.

However, the situation becomes more difficult when evidence doesn’t neatly fall into the reliable / unreliable category. Furthermore it can cause confusion where generally unreliable evidence is admitted in certain cases because of unique concerns. Expert Evidence is precisely one of these types. We will discuss these issues in greater detail below however we will give a brief overview at this point. The reasons for including expert evidence are self-evident to a point, it is a rare judge who believes he understands absolutely every piece of information that he may be presented with. The average judge may have very little grasp of the scientific probability ratio’s that underlie DNA evidence or the minutiae of the refractive index of glass. However, these issues can be central in a trial and it is thus essential if justice is to be done that a judge understands the evidence. The problem is that much of scientific advice will be opinion based, furthermore science is generally accumulative and thus inevitably there will be a degree of reliance on the work of academic peers. These attributes cause all expert evidence to fall foul of two large exclusionary rules of evidence: Hearsay and Opinion evidence. The situation thus becomes highly complex because there is an inherent tension between the principles that state such evidence is unreliable and the perhaps more fundamental principles that require any decision that may deprive an individual of liberty or property to be based on a rational and cogent basis. As we continue we will see that these principles are the guiding principles for the judiciary and that the substantive law that govern the admissibility of expert evidence embody such principles. However, their position as an exception to the rule also place an inherently contra proferentem approach whereby the courts are likely to construe the meaning of such exceptions narrowly. The inconsistency between the rules highlights a further dimension; that overall the philosophy that is guiding the growth and formation of law in this respect is far from clear.

Opinion Evidence and Its relationship to Expert Evidence

Mr Smeaton understands the construction of harbours, the causes of their destruction and how remedied … I have myself received the opinion of Mr Smeaton respecting mills, as a matter of science. The cause of the decay of the harbour is also a matter of science … Of this, such men as Mr Smeaton alone can judge. Therefore, we are of the opinion that his judgment, formed on facts, was proper evidence

  • Lord Mansfield, Folkes v. Chard (1782) 3 Doug KB 157

The issue of expert evidence is fundamentally based on practicality and common sense, unfortunately it suffers from the common deficiency of such concepts; it is incredibly difficult to translate such a nebulous concept into prescriptive rules of law. The problems associated with the concept will become apparent as we continue this discussion but just as this point I want to make clear the critical model that I’m using to assess the law in this area as it makes a large impact to the direction of the whole work. Lord Mansfield above pointed out that the evidence was taken as science and therefore as objective, these criteria for why we accept evidence are not exhaustive and as we shall it is a highly varied concept.

Frederick Schauer has written on a particularly interesting aspect of legal rules that examines the correlation between the background moral, social &c… and their translation into law. Schauer hypothesises that in a society where all the people agreed on the content of moral principles there would still be a problem over the conversion of these moral principles into coercive and authoritative social rules i.e. Law[9]. This is because for such rules to be authoritative they must be formal and strictly applicable and actually supplant moral principles[10]. However because these rules are…

‘…promulgated by human beings of finite reasoning & informational capacities & that are meant to improve the moral condition of human beings of finite reasoning and Informational capacities will always fail to capture precisely the requirements of morality

It is this so called ‘asymmetry of authority’ that this work is going to be sensitive to for the first section, the distinctive needs and justifications for expert evidence as compared to the letter of the law. It is, as stated above, highly improbable that given our finite reasoning that the law is wholly satisfactory therefore the aim is merely to assess whether the rules are under or over-inclusive as regards the justifications that we will discuss in this work. I mention this here so that the reader is fully aware of my aims at the outset.

The common law ban on opinion evidence except in the case of experts is generally traced to Lord Mansfield’s dicta in the Folkes case, above, however the recognition by society that in some cases the use of experts can be an aid to the arbitration of justice dates to significantly earlier. Hodgkinson[11] cites the 14th century case about mayhem which is mentioned in Buckley v. Rice Thomas[12] as an early authority whereby surgeons where summoned to assist the court as to whether particular wounds constituted mayhem or not because the judges lacked the requisite skill to reach a conclusion. In Buckley Saunders J made an obiter dicta remark which summed up one of the main justifications for admitting expert evidence at the time:

If matters arise in our law which concern other sciences or faculties, we commonly apply for the aid of that science or faculty which it concerns, which is an honourable and commendable thing in our law[13]

However, at the same time as this the law was woefully inept to cope with some of the more subtle distinctions that exist within our modern day legal framework. When we realise that certain evidential rules developed much later, for example at the time of Buckley an accused was not even allowed to have witnesses or even a proper defence to a murder trial. These rules developed over time and the eminent evidence scholar John Wigmore has argued that importantly for the issue of expert evidence the willingness of the courts to rely on expert evidence was very much unguided by any formal principles until the distinction between opinion and factual evidence became more formed[14]. The understanding of the interrelationship between expert evidence and the exclusionary rules on hearsay and opinion evidence becomes at this point, the early nineteenth century according to Wigmore, vital.

On a reading of the older sources prior to the advent of this distinction the courts have no clear principles guiding them. This is not per se a bad thing because it is arguable that later distinctions, particularly driven by the scientific approach to law taken by enlightenment scholars such as Bentham and Wigmore have, in the light of modern day post-modernist and realist critiques, lost much of their poignancy. However, the distinction between opinion and fact is dominant in the jurisprudence of the courts and is a very traditional part of the law of evidence. The justifications given for this ban on opinion evidence are traditionally four fold[15]; primarily the opinion of non-expert usurps the function of the jury and could lead to an undue influence being exerted by the witness on the jury members, this was pointed out by Vaughan CJ in Bushell’s Case[16]:

The Verdict of a Jury and Evidence of a witness are very different things…a witness swears but to what he hath heard or seen, generally or more largely, to what hath fallen under his senses. But a Juryman swears to what he can infer and conclude…’[17]

Another reason is that opinion evidence is largely irrelevant, which makes common sense when we think about the situations in which the rule operates. It is irrelevant if a non-expert opinion is given on an area requiring expertise as that person simply does not have the substantive knowledge to back-up an assertion of opinion. Furthermore if an opinion is given where no expertise is needed, quite apart from the prejudicial effect it may have, it is irrelevant as the decision maker is perfectly capable of forming their own opinion on the facts. Thirdly, a witness cannot be prosecuted for perjury as regards their opinion, or liable in tort for negligence[18], the law therefore doesn’t provide for any safeguards on the veracity of witness opinions. Finally, there is an established fear that the proffering of an opinion might circumvent other exclusionary rules such as relevance, hearsay and the findings of other tribunals[19]. The last justification appears to lack a degree of poignancy because the other exclusionary rules are widely known and therefore an opinion can be treated just like any other item of evidence and be excluded if it falls under those exclusions.

The impact of this distinction was revolutionary when it started to infuse legal practice in the 19th century[20] because before the fact / opinion divide was understood and substantive laws developed to represent such concerns, the use of expert witnesses was an ‘aid’ to the court that was where the reflection ended. The opinion / fact divide means that expert witnesses become an exception in their own right and thus identifiable as a particular class of evidence. This subtle change in perception means that the internal justifications of exception evidence come into play. They are an exception to a general rule and therefore the admittance of expert opinion has to be more strictly understood and that is why we see a lot of case law, in the late nineteenth century and twentieth century, that begins to flesh out the jurisprudential and substantive dimensions of the exception as awareness of the competing concerns in this area begin to infuse the judiciary.

In discussing the justifications for the expert witness exception Hall & Smith describe the overall approach that the court takes to the exception as being a rule that ‘opinion of scientific men upon proven facts may be given by men of science within their own science[21]. However the tension between expert evidence and opinion evidence is exhibited in how that overarching principle is translated into law. The purpose of the following sections is to show how the basic tensions that exist in the above internal justification give rise to different problems. An understanding of the basic justification given for using experts is immeasurably useful and ought to be borne in mind; we may well be critical in the way that the need for experts is translated into substantive law but at no point are we critical of the de facto use of experts.

1. Contradiction of Expert Evidence Law

Hodgkinson refers to there being a contradiction at the centre of expert evidence which can be clearly understood when we think out the problem logically[22]. Opinion evidence is predominantly excluded for its prejudicial effect and usurpation of the role of judge and jury, as we shall see below. The various exceptions for experts are complicated but they represent a mix between the common law reservations over opinion evidence and the need for aid in fields of expertise that it is impossible for judges and juries to make an informed decision upon. However when contradictory expert evidence is placed before the court, both of which have equal validity because of their backgrounds, the court is back in square one, as the great American judge and jurist Judge Learned Hand stated:

How can the jury judge between two statements each founded upon an experience confessedly foreign in kind to their own? It is just because they are incompetent for such a task that an expert is necessary at all[23]

The main culprit in these circumstances is the adversarial system as Davies points out:

If we were to…to design a system for the resolution of questions involving expertise, we would probably start with the idea that an expert, or a panel of experts, should decide such questions. If someone were to suggest to us…a person who had no expertise would decide such questions after hearing competing arguments from opposing experts, we would dismiss it as bizarre[24]

There are a number of reasons why the contradiction in expert evidence is symptomatic of the flaws of the adversarial system. Primarily the dichotic straightjacket that such a system forces on the presentation of evidence, especially in criminal procedure, is not suited to the presentation of scientific arguments, many do not admit of conclusive answers and cannot be wholly presented as supporting one party’s narrative. Nevertheless a retained expert may suffer from what is called the adversarial bias[25] whereby they’re encouraged to expand on the evidence that supports one side’s narrative. This practice in itself exacerbates the contradiction of expert evidence, Davies quotes an Australian judge who referred to two cases where scientific knowledge was required and two diametrically opposed scientific opinions were given[26], the quandary this leaves for the judge is two-fold. The judge or jury must assess to what extent the evidence being presented is the result of adversarial bias and what is the whole picture, the more complicated the problem the more difficult this inevitably becomes. Secondly, the judge has to come to a decision which is right and therefore requires more than anything an independent expert to help them again the need will be greater in situations of greater complexity. When we consider the general demographic of the judiciary in most cases being those well into middle-age and consider that, especially in cases of Intellectual Property, they may fall to consider some advanced technological concepts which would be wholly alien to their general education then we can see how difficult the situation may become.

There are a large number of potential solutions to these problems none of them are ideal however for our purpose the mere realisation of the dimensions of this problem are what is important. The justifications and competing arguments that we will discuss regarding prejudicial effect, aid, justice &c…which inform the main common law principles of expert evidence all have problems or distortions when they are translated into practice. This problem is one of many with the expert witness system because it means that the very reason for the exception to the exclusionary rule on opinion and hearsay is undermined. If the adversarial system causes expertise to be cancelled out then given the time, expense and potential injustices that can arise perhaps they are not the aid to the courts that they once were. If their opinion is known to be diametrically opposed by a similar expert then their opinion is as good as the judges’ or jury members’ and as they can be no aid, consequently they are frivolous and potentially prejudicial.

2. Ultimate Issue & Information in the Public Domain

The Expert Opinion must be based upon the facts, if there is an error as to the facts then the Expert may not, however skilled, give his opinion on the issue[27]. The opinion is considered to be ‘valueless[28] in the same ways as normal opinion evidence. The opinion proffered also has to be necessary in order to aid the understanding of the decision-maker in a particular case. A good comparison can be made in this respect between DPP v. Jordan[29] and DPP v. AB & C Chewing Gum Limited[30] because these cases both revolved around the impact of obscene publications on people. In the Jordan case the court upheld the ideology that jurors were able to make up their own minds and did not need expert psychological evidence as to the effect of obscene materials:

They cannot be told by the psychologist or anyone else what the effects of the material might be…since the decision has been given to the jury as representing the ordinary man, it follows that, as matters affecting the ordinary man, the jury, as such, must make it[31]

This approach has debarred certain types of evidence, one such type of evidence, which was paradigmatic until recently[32], is that of expert evidence as to witness credibility. This approach is not unanimously supported for example in Scotland there are a number of cases and articles on the issue. Raitt[33] has suggested that in certain cases there is considerable doubt over whether or not a typical juror or judge can understand the issues that may effect witness credibility. The examples that she gives is victims of domestic abuse and victims of child abuse, the nature of these crimes and the potential psychological effects on a witness are potentially completely alien to the experience of most jurors and judges[34]. In R v. Turner the court laid down the reasons why such evidence ought not to be admitted:

authority for the proposition that in all cases psychologists and psychiatrists can be called to prove the probability of the accused's veracity. If any such rule was applied in our courts, trial by psychiatrists would be likely to take the place of trial by jury and magistrates[35]

The courts have now reconsidered that the science is now stable enough and as we shall see the intermingling between this issue and the issue of reliability is quite large. The development of this rule in comparison to some of the continental jurisdictions gives us an interesting comparison of the underlying motivations in the UK system. The judge in both South Africa and other civil law jurisdictions posit the judge as the ultimate trier of fact so the test laid out in Turner as to the admissibility turning on the helpfulness is treated more literally. The judge asks whether this or that piece of expert evidence would truly be of use to him in coming to a decision in the particular case. However, as we have seen above the concern of English law is not so much on a strictly ‘helpful’ basis because it is interpreted to have more to do with the Ultimate Issue rule that we will discuss below. This means that there is an emphasis on the normal / abnormal sphere divide[36] and the judges sit as arbiters of that divide. The arbitrary nature of this divide has been questioned using similar studies to that of Raitt, above, and the point has been made that ‘much common behaviour is 'demonstratively counter intuitive in the sense that "ordinary men and women" generally misunderstand [it][37].

In A,B &C the court considered another prosecution under the Obscene Publications Act 1959 similar to Jordan however as the target audience was children rather than adults, psychological evidence was allowed because ‘any jury and any justices need all the help they can get[38] when it comes to children. Lord Wilberforce commenting on the nature of the distinction in Jordan stated:

‘To this general rule there may be an exception in a case where the likely readers are a special class, such that a jury cannot be expected to understand the likely impact of the material upon its members without assistance. In such a case evidence from persons qualified by study or experience of that class may be admissible’[39]

This kind of distinction is seen across the board as regards expert evidence and forms a wider rule that the opinion of an expert is not necessary or helpful where there is not some identifiable body of science which is not considered to be understandable by the average person[40]. In R v. Masih[41] the court specifically stated ‘in order to enlighten the jury upon a matter which is abnormal and therefore, ex hypothesi, presumably outside their experience’ then expert evidence will be allowed. The decision is one of pure discretion and a systematic study of what is allowable would be almost obsolete by the time it was written because of the variation in what is considered in the public domain. Zuckerman specifically states on this issue:

A judge deciding whether expert opinion should be accepted as an arbiter of a certain matter has to consider the state of public opinion on the point. If the community has come to defer to professional standards on the matters in question, the courts will normally follow suit[42]

This issue will become more pertinent later on when we discuss the courts attitude to new technologies and medical evidence. The law has exhibited a degree of incoherence and particularism in its application of the normal / abnormal divide which is, as we stated, inherently likely to occur because of its discretionary basis. In R v. Lowery[43] which allowed psychological evidence in the case of two adults, on the face of it this seems to be contrary to the decision in Jordan above and the general rule against having expert evidence on an area considered in the public domain. In that case Lord Morris justified his admittance of such evidence by stating ‘When an accused person put his character in issue, he is in effect asking a jury to take the view that he is not one who would be disposed to have committed or would be likely to have committed the crime in question… if an accused person is not of good character, the law has been firm’[44]. This tenet of the law has become one that centrally justifies the existence of the rule, the expert’s role has always been one of ‘aid’ since its very inception however that aid is circumscribed to fall only in those categories which the court decides it requires such aid. However, the tension between the aid an expert opinion can give the court and the perceived potential prejudices of such aid mean that the law goes onto circumscribe the role of an expert.

The distinction that Lord Wilberforce was making in Jordan is significantly related to the more fundamental rule that Expert Witnesses cannot give evidence on the ‘ultimate issue’. This concept is very vague but is a product of both the tension I mentioned above between the expert evidence exception and the general rules of evidence as well as the potentially determinative weight that will be given by a lay person to such evidence. The basic premise of the ultimate issue rule is that the expert shouldn’t give an opinion on any issues which it is for the judge or jury to decide, the classical position was outlined by Cresswell J in National Justice Compania Naviera SA v. Prudential Assurance Co Ltd[45] where he remarked that ‘An expert witness should provide independent assistance to the Court by way of objective unbiased opinion in relation to matters within his expertise’[46]. The idea of ultimate issue is perhaps best understood by use of an example. It would be inappropriate to ask a medical expert in a medical malpractice case whether the accused’s behaviour fell short of that required by a professional doctor. However, Lord Taylor, in a separate case in the same year as National Justice, made an obiter dicta remark about the practical operation of the rule:

‘The rationale behind the supposed prohibition is that the expert should not usurp the functions of the jury. 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’[47]

Thus, in our malpractice situation we can see how a skilled advocate might ask questions which have obvious inferences on the standard of the accused’s behaviour by directing the expert to explain what common medical practice in the particular situation is. As an ancillary issue to those started here it is worth pointing out that the courts have made it quite clear that they need not accept the experts advice, as was stated in Re B (a minor) (care: expert witness) ‘the parties have invoked the decision of a judicial tribunal and not an oracular pronouncement by an expert’[48]. This situation was discussed in Liddell v. Middleton[49] where the judges were highly critical of the parties in bringing expert witnesses in a road traffic accident where there were eyewitness accounts and they specifically stated:

There has been a regrettable tendency in recent years in personal injury cases, both road traffic and industrial accidents, for parties to enlist the services of experts whether they are necessary or not. When they are not necessary, they simply add to the already high cost of litigation and the length of the trial[50]

However the judge must not simply substitute his decision for the expert’s where there is nothing to contradict unanimous expert evidence in favour of the accused[51]. In Bolitho v. City and Hackney Health Authority[52] Lord Browne-Wilkinson discussed the role of the judiciary and whether it was one of deference or education, primarily he laid town a test that where in certain cases ‘it cannot be demonstrated to the judge’s satisfaction that the body of opinion relied on is reasonable or responsible’[53] furthermore he went on to state his opinion on the level of deference a judge ought to pay to an expert:

‘In my view, it will very seldom be right for judge to reach the conclusion that views genuinely held by a competent medical expert are unreasonable. The assessment of medical risks and benefits is a matter of clinical judgement which a judge would not normally…make’[54]

The rule on ultimate issue may well be under threat if we are to believe the dicta of Lord Taylor above however there are definite limits. The ultimate issue rule does still exert a certain pressure in determining the line between what is acceptable and what is unacceptable in actually giving evidence[55] for example the courts have been quite clear that an expert should not under any circumstances opine what he would have done if he was in similar circumstances to that of the accused[56]. One of the more recent decisions on this issue was in Pride Valley Foods Ltd v. Hall & Partners (Project Managers)[57] where Toumlin J was very emphatic in his condemnation of the reports prepared in that case, he specifically relied on Pozzolanic Lytag Ltd v Bryan Hobson Associates[58] and the judgement of Dyson J in that case, Toumlin J in particular stated:

Many of these are questions for the court and not questions for the experts… He purports to make many findings of fact on questions which are matters for the judge…His report offends against the established basis on which experts should give evidence[59]

It must be remembered that these cases are civil cases and as such the rules are slightly distinct however as regards the rule on ultimate issue both the civil and criminal seem to have identical tests.

The academic commentary on this rule has also been unfavourable and it is claimed that the rule is open to a very large degree of criticism. The main justification of the rule is premised on a belief that the jury might be overly influenced by an expert which is a false assumption in the case where it is a professional judge sitting alone. It has been said to in fact be wholly antithetical to the whole underlying justification for having experts namely that ‘the drawing of inferences from the facts in question calls for an expertise which the tribunal of fact does not possess’[60]. A final reason why this rule is considered to be inconsistent is that there is a high frequency of disagreements between experts in the case law in any case so it will be very rarely that there is unilateral incontrovertible expert evidence in favour of one party. Therefore the prejudicial effect of this rule has to be questioned, reinforced by its absence from the Civil Law of procedure and its almost complete invisibility from day to day Criminal law procedure[61]. The problem with such an approach of quasi-existence is clearly undesirable and offends against principles such as the rule of law.

The law has always recognised that experts have a role to play however what was described by Wigmore as the fact / opinion divide was part of a whole movement in philosophical, jurisprudential and evidence scholarship which insisted on the use of exclusionary rules of evidence. Holdsworth in discussing this development identified that these exclusionary rules of evidence were the work of the sixteenth and seventeenth century[62] and in particular the rise of the belief that ‘law of evidence…is distinct from the logical processes of reasoning; but it is based upon and assumes the existence of these processes’[63]. Holdsworth is making an interesting point here, which is related to our exercise, in that many of modern day evidential rules such as burden of proof and exclusion of certain facts as inadmissible flow directly from instinctive reasoning processes and the application of logic in a system of relative free proof:

‘Thus the rules which flow obviously from the principles of reasoning have been overlaid by a mass of technical rules, which represent the ideas and needs of many different periods in the law of procedure’[64]

Twining again referring to this sort of overlapping and intermingling progression of the rules of evidence identifies that there are many competing concerns[65]. He identifies the rule of Hearsay as starting around the sixteenth century, so we may reasonably infer awareness of the issues of opinion evidence and experts as an exception to that point. The issues we raised in this section regarding the role of expert as an aid and also the restrictions on testimony as to the ultimate issue show these competing concerns. Clearly the dominant concern in excluding opinion evidence is that the evidence could potentially be considered by a decision-maker despite its potentially unreliable nature[66] however, in some cases an informed opinion will not be unreliable and thus in those situations an expert will be allowed to aid the court.

The concerns regarding experts only being called in cases where there is a genuine area of expertise not in the public domain were exemplified in R v. Turner, above, where it was stated that the existence of scientific qualifications and use of scientific jargon on matters of normal human behaviour may not be ‘any more helpful than that of jurors themselves; but there is a danger that they may think it does[67]. The danger of overemphasis on pre-ordained unreliable evidence is one of the central motivations for the exclusionary rules of evidence and we can see it playing a large role here. The rule on no evidence on the ultimate issue furthermore exhibits such a sensitivity to background principles and the courts’ approach is clearly motivated by the desire to avoid trial by expert. However, the obvious artificiality of this test, as recognised in Stockwell, has forced reconsideration in the logic which motivates this rule. Robertson & Vignaux[68] point out that an expert in expressing an opinion as to the ultimate issue may well make certain assumptions about prior odds. The main example would be where a forensic expert giving evidence as to the match between the accused’s blood and that found at the crime scene expresses an opinion as to the accused’s guilt. There are certain assumptions that an expert may be making which may be invalid and it is wise to bear in mind that an expert may well only be operating from a more limited set of facts than the court has available to itself[69].

The understanding of these various competing concerns is interesting because to a degree the problems in the rules that we identified cut both ways. The background principles are translated into rules that in some sense are both under and over inclusive. The need to rely on experts but the desire to limit their privileged position in giving an opinion to the court appear to war against each other.

3. Peritus and Role of the Expert Witness

Another basic common law rule which tells us a lot about the way that the law treats expert opinion is the fact that an expert witness need not have any formal qualifications as such but the judge will determine whether he exhibits a sufficient degree of expertise. The leading case in this area is R v. Silverlock[70] where a solicitor who had gained expertise in handwriting comparison through an amateur interest in the area which had been put into practice. Lord Russell CJ stated that there was no test of expertise rather the correct approach was for the judge to ask ‘is he peritus? Is he skilled? Has he an adequate knowledge? Looking at the matter practically, if a witness is not skilled the Judge will tell the jury to disregard his evidence’[71]. In more modern times the law has upheld ‘informal’ experts in various situations such as a police officer’s experience in traffic accidents qualified him as an expert[72]. In Westminster City Council v. McDonald[73] the court held that expert opinion as to noise was admissible even in the absence of sophisticated technology or techniques. The best summing up of the law was given by Tyrwitt Drake CCJ in R v. Bunnis[74]:

‘The test of expertness, so far as the law of evidence is concerned, is skill, and skill alone, in the field of which is sought to have the witness’s opinion…It is not necessary, for a person to give opinion evidence of a question of human physiology, that he be a doctor of medicine’[75]

The interesting thing about the approach of the courts here is that it uncovers a more liberal approach in the courts thinking, a willingness to treat expertise at face value and not debar certain origins of those expertise. The common law rules we examined in the previous section were borne of a tension between the competing concerns of the court. Commentators have questioned this approach, especially in light of the ‘obvious dangers’ of relying on expert testimony of a ‘questionable reliability’[76]. The approach is also not precisely harmonious as ss 1(1) and 2 of the Criminal Procedure (Insanity and Unfitness to Plead) Act 1991 require specifically qualified experts before an acquittal based on the defence of Insanity only on the basis of two or more registered doctors, at least one of whom is approved by the Secretary of State as having appropriate expertise. However it is clear that this is an accepted approach given that an identical test is administered in other jurisdictions[77] . This seems to be adequate evidence that there is scope for variation on this point.

The role of the expert witness is also an interesting position, unlike other witnesses who although sworn to tell the truth do not owe a duty to the court above that of the party calling them. An expert witness does and Lord Wilberforce commented on this aspect in Whitehouse v. Jordan[78] stating that ‘whilst some degree of consultation between experts and legal advisers is entirely proper it is necessary that expert evidence…should be…the independent product of the expert, uninfluenced as to form or content by the exigencies of litigation’. The somewhat nebulous definition was given considerable judicial attention in the case of National Justice Compania Naviera SA v. Prudential Assurance Company Ltd[79] where the court set out a number of key aspects of the role of the expert witness:

  • Objective unbiased opinion to matters within his expertise
  • State the facts upon which assumptions are based
  • Make it clear when an issue falls outwith their expertise
  • If there is insufficient data then he should inform the court that opinion is provisional
  • Any change of views after an exchange of reports should be communicated to the other side.
  • Any real evidence upon which opinion is based should also be provided.[80]

This is summarised by Swann as boiling down to a general duty for the expert to ‘advise the judge, to undertake assessment, to give an opinion and consult with other experts’[81] this was all to be done in a spirit of ‘integrity and objectivity’[82].

An interesting set of facts occurred in Liverpool Roman Catholic Archdiocesan Trustees Inc v. Goldberg (No 3)[83] where it was admitted by the expert that he had a personal relationship with the defendant. The judge felt that it was just as important that justice is seen to be done and therefore the lack of independence on the part of the expert making him more favourable to one party made his evidence inadmissible. This case highlights the tension between the judiciary’s commitment to having the aid of an expert to understand the full facts of a case and in turn upholding the ideology that certain evidence ought to be excluded because of its potentially prejudicial effect. Although not directly concerned with the role of the expert it is a further limit upon their ability to appear in a court of law. It has been stressed by many commentators that fundamentally the right of an expert to appear in the court and not to be subject to the strictures of normal evidence law is to be treated as a privilege[84]. This privilege has been extended in a haphazard and often incoherent manner and it is not altogether unsurprising that academic attempts at rationalisation will generally fail to capture the entire nature of the courts approach.

The role of the Expert witness in the legal arena has been an area of great controversy for the last decade ever since the ‘Access to Justice’ reports in the mid-1990, also known as the Woolf Reports[85]. The focus of Lord Woolf was the prohibitive cost of litigation which was in part contributed to by the ‘multi-million pound fee income[86] industry that pervaded professions as wide and varied as Accountancy and Architecture. In addressing one of the major problems that this presented for both the Criminal and Civil Justice system Lord Woolf considered the main problem was that the adversarial system had a distortive effect on the role of the Expert:

There is wide agreement that the expert's role should be that of an independent adviser to the court, and that lack of objectivity can be a serious problem…The present system has the effect of exaggerating the adversarial role of experts, and this helps neither the court nor the parties[87]

The tragic miscarriages of justice in the cases of Angela Cannings, Sally Clark and Trupti Patel show that even the limited reforms that flowed from the Woolf Reports have not improved the situation, at least not in the Criminal Justice system[88]. There are numerous medical and legal articles detailing the fact that experts feel an inherent pressure from a solicitor in presenting evidence and there is a great deal of cynicism, as shown by the observation that ‘it is quite surprising to see with what facility and to what extent, their views can be made to correspond with the wishes or the interests of the parties who call them[89]. A leading report was published in 2004, in the wake of the criticism of Sir Roy Meadow’s evidence in the Clark and Cannings trials, by the Royal College of Pathologists and the Royal College of Paediatrics and Child Health Care which again highlighted that medical experts in trials were falling prey to the pressure of giving evidence in support of their ‘side’ and furthermore they were relying a lot more on ‘medical belief rather than scientific evidence[90]. The adversarial bias was hoped to be solved by the Woolf report with reference to a prescriptive duty on the expert witness that ‘provide[s] that when an expert is preparing evidence for potential use in court proceedings, or is giving evidence in court, his responsibility is to help the court impartially on the matters within his expertise. This responsibility will override any duty to the client[91].

Whilst, as I have mentioned above, we have to be careful about drawing analogies from the civil sphere[92] given that there are quite distinctive approaches to expert evidence, in this issue like the rule on evidence as to the ultimate issue there is a significant degree of overlap. In Cala Homes (South) Ltd and Others v. Alfred McAlpine Homes East Ltd[93] there was a lesson for any budding expert witness to take on board as Laddie J ripped an experts evidence to shreds because of an attitude displayed in an article he had published where he intimated that his opinion was that an expert should treat a judge as a ‘rustic’ who could be susceptible to a Three Card Trick by presenting an argument wholly favourable to the side instructing the expert. Laddie J stated in this issue:

Most witnesses would not be prepared to admit at the beginning of cross examination, as Mr Goodall [the expert], effectively did that he was approaching the drafting of his report as a partisan hired gun. The result is that the expert’s report and then his oral evidence will be contaminated by this attempted sleight of mind[94]

Laddie J had admitted that Mr Goodall was an eminent Architect in his area but as a result of this tendency to completely ignore his duty to the court and present a wholly one sided argument the judge stated that in coming to a conclusion on the issues at hand in the case he had effectively ignored Mr Goodall’s advice. This is obviously an extreme example of somebody who tempted the wrath of the court by espousing a highly derogatory opinion that judges could be deceived by the trickster expert. Nevertheless, the question that begs itself is how many people read the article by Mr Goodall and accepted his advice? These people can go undetected and their prejudicial advice could have a serious impact on the direction of the case[95]. Furthermore this problem is undoubtedly exacerbated by the pressures from clients on solicitors to produce partisan expert witnesses. It is clear that this pressure will be of the utmost in a criminal case where the stakes for the client are his liberty. The adversarial culture which reveres the art of advocacy and persuasion undoubtedly has its own inimical pressures to win which it is hard to see being dissipated whilst the decision to call experts rests in the hands of the respective parties. The solutions that have been suggested by reports such as Woolf have had little impact so far and there are still reports of adversarial bias that surface regularly[96]

The idea of imposing a duty of neutrality on an expert witness in an ironic manner exhibits the precise ignorance of the true nature of science in the courts that causes so many problems in relation to expert evidence. There is an unchallenged assumption that in relation to experts that somehow forensic science and pure science are the same thing or at least share common principles. The main one for our purposes is the assumption that they conceive all science as the ‘disinterested pursuit of the truth under ideal conditions of inquiry[97] however in general most crimes do not start with ideal preconditions such as uncontaminated environments and unlimited source material. The realisation of the extent to which ‘behind this apparently objective, definitive conclusion lies a succession of more subjective and equivocal judgements[98] impacts considerably on the status we attach to experts. The problems is that as a general rule the answer ‘I don’t know’ is rarely seen as an acceptable answer and any attempt to highlight these numerous subjective steps may well be flawed and reduce the evidence to incomprehensible. It will be flawed primarily because many of the subjective leaps may be subconscious.

A further dynamic that ought to be considered in marrying the role of the expert to that of the courts is the simple fact that the system of criminal justice is not an out and out search for the truth[99]. The complaint sheet, which is served on an accused in a criminal case will usually see a summary of the facts of the case, the case then proceeds on the truth of the allegation and not on the truth of the whole circumstances. Positing an expert as an independent advisor to the court doesn’t sit well with this position because it is inimical to the position of the parties. If it goes to trial then the accused is pleading not guilty, in effect denying the allegation, the defence are not going to call an expert witness who may give prejudicial evidence for their side. An interesting judgement was handed down in the case of Manchester City Council v. B[100] by Justice Bracewell because it dealt with two medical experts who were declared to have exhibited a considerable degree of disagreement[101]. In this case there was no discussion of adversarial bias however the judge did refer valuably to her thought process. She felt that the distinctive conclusions that the scientists came to in this case where not as different as they first appeared because:

Each expert draws on their own clinical experience together with the research evidence. It is not, and cannot be, an exact science because assumptions frequently have to be made by medical experts as to the basic underlying and background facts and any differential diagnoses

Justice Bracewell seems here to be making a point which goes directly to the heart of the issue in this case which is that adversarial bias is one factor but the nature of forensic science is another. This case is not overly reported and I only found reference to it in one article[102] and even then it was fleeting. However, I think that as we begin to build up a healthier understanding of the controversies that the role of the expert evidence can raise, this dicta suggests taking a novel and simplistic approach[103] to expert evidence which is to take as a pre-requisite that scientific differences can be weighed in an ordinary judicial manner with reference to underlying assumptions that experts may have made. The recognition of scientific conclusions being sensitive to their initial conditions is hardly revolutionary[104] but laid down in some form of statutory or informal guidance to the judiciary this kind of approach could significantly impact on the coherence and unanimity of decisions on expert evidence.

A different approach was suggested in the case of Re C[105] where the judge was of the opinion that there ought to be collaboration between all the experts brought before the court before they presented evidence. The advice presented ought to be in the form of two conclusions on each of the two competing allegations. This approach whilst in some ways beneficial also has to be criticised given that these conclusions are discussed out of the courtroom and opinions may harden where before they were more flexible.

The Criminal Justice Act 2003 now requires the defence to disclose any medical reports that it may commission in the preparation of the case, whether presented in evidence or not. The problem with this situation is that it is far from clear that this will somehow help overcome any adversarial bias on the behalf of experts or deal with the problem of the nature of the adversarial system. It will merely suppress the use of experts by defence agents, even in cases where expert evidence could be of vital importance. The rationale for such a change is difficult to accept as ‘the only people who would take such a blind risk are those with nothing to lose. Perhaps those in authority take the view that the innocent have nothing to fear[106]. Any proponents of that particular view should ask Sally Clark if she feels the innocent have nothing to fear from the use of experts.

The issue of the role of the expert is one which is fraught with difficulty and contradictions. Science is not suited to give definitive advice on one side of the problem, therefore different scientists will come to varying conclusions; the judiciary has no such luxury it must come to one definitive solution. The adversarial system prima facie would seem to be the best forum for such differences of opinion to be resolved in. The classical notion of two opposing sides evincing the most cogent evidence on their side putting all the evidence before an independent judge in theory seems ideal. However, the adversarial bias and the tendency of experts to overstate their science or present their conclusions as definitive are unhelpful and could lead to serious miscarriages of justice. The issue certainly seems to fit the colloquial saying ‘damned if you do and damned if you don’t’.

4. Daubert & The Extent to which we utilise Expert Evidence

This is the final section of our discussion of the general principles of Expert evidence and touches on a number of the issues that we have discussed before in regards the admittance of expert witnesses. In the American case of Daubert v. Merrell Dow Pharmaceuticals Inc.[107] the United States Supreme Court discussed when the courts generally ought to admit expert evidence and the test that they formulated has controversially been used around the globe. This subject matter more than any has churned out a library worth of resources, the full breadth of which it is not possible to give here. This issue is particularly controversial in the U.S.A however, whilst this issue is extremely important and raises a lot of insightful points we must avoid becoming blinkered and realise that the sociological pressures of the world of Expert evidence can be particularly demanding on any expert in particular the lack of suitability for the presentation of scientific hypothesis in determinative statements of fact in the trial setting[108].

The simple wording of the judgement belies its effect on the role of the judge in allowing expert evidence the court stated that ‘the trial judge must ensure that any and all scientific testimony or evidence admitted is not only relevant, but reliable[109]. The concept of reliability has lead to the casting of the judiciary as the gatekeepers in this respect and the Daubert court emphasised three factors which would generally guide the judiciary in coming to a decision over the reliability of an expert[110]. The first was whether proper methods of hypothesis testing were used, flowing from this the judge ought to be able to tell whether the result was falsifiable. Furthermore they need to consider the failure rate of the method and the standards controlling the technique in question. Thirdly, they ought to consider the level of peer-review and acceptance that such techniques generally attract in the scientific sphere that the work is concerned with. The court in Daubert summed up by stating that their may well be a place for the test of general acceptance:

Widespread acceptance can be an important factor in ruling particular evidence admissible, and 'a known technique which has been able to attract only minimal support within

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