In some cases there is a statutory requirement for a witness to be formally qualified; such as those that involve the defence of insanity, where a jury cannot reach the special verdict of, 'not guilty by reason of insanity,' except on the evidence of two or more registered medical practitioners, at least one of whom is approved by the Secretary of State as having special experience in the diagnosis or treatment of mental disorder.
On the issue of diminished responsibility,17 "… while s. 2(1) of the Homicide Act 1957, does not require that medical evidence be adduced, it makes it a practical necessity if the defence is to begin to run at all. " 18 It is not essential that in all cases the expert possesses formal qualifications in the relevant field of expertise. Commonly, if there are some credentials, the evidence is likely to be admitted and the rest would be a matter of weight. In R v. Silverlock,19 opinion evidence from a solicitor was admitted with respect to hand writing, even though he did not posses any formal qualifications in that field but merely studied it as a hobby.
Expert opinion evidence is not admissible per se in all criminal trials. Where the issue is one for which the jury is able to decide and form their own opinion without the assistance of experts, the matter being within its own experience and knowledge, such evidence is inadmissible. The reason is because such evidence is usually unnecessary and irrelevant. 20 "… trial by psychiatrists would be likely to take the place of trial by jury and magistrates. We do not find that prospect attractive and the law does not at present provide for it". 21 In R v.
Chard,22 evidence from an expert with regard to the alleged inability of the accused to form the necessary mens rea of the offence was disallowed by the Court of Appeal. The Court emphasised that where there was no issue of mental instability or illness, it is inappropriate to allow evidence from a medical witness as to the state of the accused's mind. 23 Likewise in R v. Turner,24 where the accused's defence was one of provocation. The Court of Appeal excluded evidence from a psychiatrist because there was no issue regarding his mental state.
The issue of provocation was one which the jury could decide. Lawton LJ stated in Turner, "… the fact that an expert witness possessed impressive scientific qualifications did not necessarily make his opinions on matters of human nature any more helpful. These were matters for which the jury was competent to decide". 25 These cases are interesting when one considers the nature of the 'expert' testimony on voice identification given by the witness in, Robb! The Privy Council in Lowery v.
The Queen,26 held that the restriction on the admissibility of expert evidence, includes a restriction on the credibility of a witness or the accused, save in exceptional circumstances. Turner can be reconciled with this decision since, in the circumstances of Lowery, it appears that the jury needed expert assistance in relation to the relative aggression of the two accused. Moreover, irrespective of this, Lowery had testified on his own behalf and had already mentioned his own good character. The psychologist's evidence was admissible in rebuttal.
Although such evidence was admitted in Lowery, some commentators regard this decision as applying only to the specific facts of the case rather than establishing any general principle. 27 This approach appears to be correct in the light of R v. Rimmer,28 where the trial judge refused to allow the evidence of an expert on the basis that this related only to the credibility of the accused. At one time there was also the rule that expert opinion evidence was inadmissible on the ultimate issue in the case.
Traditionally, this rule prevented the expression of opinion on the very point that the trier of fact was to decide; primarily this was seen as a usurpation of the function of the jury. 29 In many civil trials, the rule was evaded and the expert was able to express an opinion on the final issue so long as it was couched in different language to that employed by the court. Finally, the rule was abolished by Parliament in 1972. 30 This was followed by calls for a similar reformulation in respect of criminal trials31 and Professor Murphy suggests that, '…
the English common law should now permit expressions of opinion by experts on ultimate issues, subject to the power of the judge in a jury trial to limit testimony in any case where there is a danger of the jury according the testimony undue weight… '32 It is clear that whilst the rule still exists, in practice expert evidence on the ultimate issue is allowed in many cases. Subject to the earlier civil evidence rule: 'so long as, the diction employed is not noticeably the same as that which will be used when the matter is subsequently considered by the court. '33
Thus the rule has become 'a matter of form rather than substance'. 34 In DPP v. A & BC Chewing Gum Ltd. 35 Lord Parker CJ stated that, "Those who practice in the criminal courts see every day cases of experts being called on the question of diminished responsibility, and although technically the final question, 'Do you think he was suffering from diminished responsibility? ' is strictly inadmissible, it is allowed time and time again without objection. "36 The difficulty with expert opinion evidence is that sometimes the expert relies on the work of other individuals.
For example, a pathologist might well rely on an analyses of stomach contents or body tissues which was carried out by others. Thus the expert witness, the pathologist, has no first hand knowledge and this, if retailed to the court, would offend against the rule of hearsay. In R v. Bradshaw,37 the Court of Appeal held that the evidence of the psychiatrists, on the condition of the accused, was hearsay and inadmissible as this had been entirely based on the fact that the accused had told them that he was, 'in a state of unreality and confusion'.
The court found that the doctors could not testify to such statements as proof of their truth, but they could testify to them in order to explain the basis on which they arrived at their conclusions about the defendant's mental condition. By way of contrast to Bradshaw, in R v. Abadom,38 the Court of Appeal held that the primary facts, upon which the expert opinion was based, (the refractive index of the glass), was direct admissible evidence, although the expert had relied on secondary information, the statistics supplied by the Home Office Central Research Establishment.
The court decided that the expert was entitled to rely on this research in forming his opinion and that this did not violate the rule against hearsay. They did however, go on to say that, "these are in our judgement the limits of the hearsay rule in relation to evidence of opinion given by experts, both in principle and on the authorities". In civil proceedings prior to 1995, expert testimony was a legitimate technique to circumscribe the hearsay rule. However, since the Civil Evidence Act 1995 came into force, no evidence can be excluded on the ground that it is hearsay, of whatever level.
Although at one time there was no statutory provision covering the admissibility of expert reports in criminal cases, s. 30 of the Criminal Justice Act 1988 has now changed that. By virtue of s. 30(1) of the Act, an expert report is to be admissible as evidence in criminal proceedings whether or not the person making it intends to give oral evidence in those proceedings. However, by s. 30(2), where the expert does not testify in court, the written report would be admissible only with leave of the court. In deciding whether to grant leave, the court is directed to consider the various matters listed out in s. 30(3), including the risk that the admission of the report will result in unfairness to the accused.
Given that an expert report is admissible evidence in its own right, unlike a witness statement, it is worthy of note that there is no reason why the jury should not take the report with them when they retire to consider their verdict. It ought to be remembered however, that studies have shown that juries often find expert evidence compelling and when that evidence is in black and white and sitting in front of 'twelve ordinary members of the public,' its effect may be increased substantially.
40 Professor Murphy feels that, 'the courts have not always accorded to expert evidence the recognition it deserves, perhaps because of the risk that a witness who usually receives a fee for his appearance may, with less than true scientific objectivity, render an opinion unduly favourable to the party calling him'. 41 This, it is submitted, is perhaps a little cynical given the general standing of most expert witnesses. It has recently been reiterated in the Court of Appeal, that an expert witness should be objective and should not attempt to be an advocate for the party calling him.
42 It is suggested that although it can still be said in general, that opinion evidence is not usually admissible, in situations where it is, the courts have put in place vigorous safeguards to ensure that it is admitted only in appropriate circumstances. Furthermore, putting the issue of independence to one side, it is submitted that expert opinion is hugely preferable to a dogged adherence to direct evidence which can produce perverse results such as was seen in Bowden v.
Bowden,43 where the direct evidence of a mother in a paternity case, that she gave birth more than ten months after conception, was preferred over the opinion of several doctors to the contrary!
Books Andrews, J. A. Criminal Evidence Statutes & Materials Waterlow, London 1990 Keane, The Modern Law of Evidence 3rd Ed. Butterworths, London: 1994 Lane, B. The Encyclopaedia of Forensic Science Headline, London: 1992 Lewis, G. R. Illustrations of Phrenology 1 (1840) 1 July 6 & Phrenological Journal No. XCIV (1892) December Lombroso, C. L'Uomo Delinquente 1876