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  Experts and the ultimate issue

The rule against an expert giving an opinion on a matter that is for the jury or the judge to determine is becoming very strained

It had long been a rule of evidence at common law that a witness – and that included expert witnesses – should not give evidence in relation to what is termed the ‘ultimate issue’ (i.e. any fact in issue) in a case. The rule applied in both the civil and criminal courts, and was based upon the principle that a matter that is for the jury (or the judge) to decide should not be usurped by a witness.

So, for example, a fingerprint expert witness could state, with varying degrees of certainty, whether fingerprints found on a murder weapon were a match for those of the accused. He was not, however, permitted to go beyond this and say that, in his opinion, the accused was the murderer. Guilt or innocence was a matter for the jury to decide, and the prohibition on expert witnesses addressing the ultimate issue was designed to prevent trial by jury being supplanted by trial by expert.

In DPP -v- A and BC Chewing Gum1, Lord Parker CJ said that, while an expert in child psychiatry was competent to give an opinion on the effect of battle scenes on children, it would be wrong for the expert witness to give his opinion on whether any of the defendant company’s products containing such images actually tended to corrupt or deprave ‘... because that final stage was a matter which was entirely for the justices’.

This basic premise of the ultimate issue rule was also outlined by Cresswell J in the Ikarian Reefer2 in 1993. The expert should only give evidence in relation to matters within his expertise and on issues not within the ordinary experience of the jury. If the jury is capable of forming an opinion without the assistance of an expert because the matter is within their own experience or knowledge, then expert opinion is not necessary.

Weakening of the rule

For some time there has been an ongoing and steady weakening of the rule against expert opinion on the ultimate issue. The 1972 Civil Evidence Act made expert opinion on the ultimate issue admissible in civil cases, giving effect to the 1970 Report of the Law Reform Committee on Evidence of Opinion and Expert Evidence. This report recommended that ‘... a statement by an expert witness... shall not be inadmissible upon the ground only that it expressed his opinion on the issue in the proceedings...’. In criminal cases, the abolition of the rule was recommended by the Criminal Law Revision Committee in its Eleventh Report (Cmnd 4991 (1972) p. 155), but this recommendation was never put into effect.

However, even in civil cases, there remained definite limits on the extent to which opinion on the ultimate issue would be admissible, and the common law rule continued to exert pressure in determining the line between what was acceptable and what was not.

In Pride Valley Foods Ltd -v- Hall and Partners3, an expert witness in a construction law case gave an opinion on what he would have done if he had been in a similar position to the defendant. In doing so, he was directly addressing questions relating to the ultimate issue. Toumlin J said that these were not questions for expert witnesses but were matters for the court to decide. The expert, he said, purported to make findings of fact on matters that are for the judge, and that his report offended against the established basis on which experts should give their evidence.

Complexity rules

However, with increasingly complex areas of evidence, and particularly those involving medical malpractice, fraud or forensic science, the boundaries between acceptable expert opinion and opinion that addresses the ultimate issue have become blurred. In fraud cases, for example, expert accountants have given opinions which effectively state that there can be no rational, honest explanation for the transactions under consideration, thus inferring that the only remaining explanation is one of fraud.

In the same year as the Ikarian Reefer case, Lord Taylor stated, as an aside, that:

‘... 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’.

For example, in a medical malpractice case an expert witness cannot be asked to state, outright, whether a doctor’s behaviour has fallen short of that expected by a professional doctor. However, it is easy to see how a particular line of questioning by an advocate might elicit an inference from an expert that is not too far removed from an opinion on the ultimate issue.

In 2006 we reported on cases that dealt with the emerging science of human memory research, particularly the reliability or otherwise of childhood recollection (see Your Witness 45). In R -v- S:R -v- W 4, the appellants sought to adduce fresh evidence from an expert in human memory. Both had been convicted of sexual offences against children. The two children in question had been aged between 6 and 8 and 3 and 11 years at the time of the offences, but were aged 20 and 27 years at the time of trial.

The fresh evidence concerned childhood amnesia. It sought to show that the detail contained in the witness statements was such that it could not be consistent with normal childhood memories and was consequently unreliable. In considering whether such evidence should be admitted, the court was concerned that the nature of the evidence spoke to the ultimate issue in the cases. If the expert witness evidence was accepted, it would tend to suggest that the victims’ statements could not have been based in fact but, instead, were likely to have been fabricated, whether consciously or otherwise. The truthfulness of the victims’ statements was a question for the jury and not for expert evidence. Accordingly, the appeal was dismissed and the fresh evidence was not allowed.

Facing facts

Facial mapping is another area where the courts have considered the admissibility of expert evidence on the ultimate issue.

In R -v- Gray5, the Court of Appeal held that, because there was no evidence of a national database of facial characteristics, or any accepted statistical formula for determining the probable occurrence of a particular characteristic or combination of characteristics, an expert witness should not go further than to say that the accused and the offender shared certain facial characteristics; he should not seek to opine on whether the evidence provided ‘strong support’ of identification of the accused. The cogency of the expert opinion in relation to identification was a matter for the jury.

However, more recently in R -v- Mitchell 6, it was accepted that a facial mapping expert can give an opinion on the likelihood that the accused is the offender if the jury is shown (and provided with) high-quality images and has the matches pointed out to them. This is particularly so if the judge gives an adequate direction on the evidence.

Mitchell was followed by the court in the case of  R -v- Atkins 7, where the judge allowed a facial mapping expert to provide an assessment of the likelihood that the accused was the offender, notwithstanding the absence of a national database of facial characteristics. It was held that the limit imposed by Gray could actually result in the jury giving too much weight to the evidence – a result the judgment had been designed to avoid.

The only safeguard for the accused is that the trial judge must explain to the jury in clear terms that a facial mapping expert’s opinion is not based upon a database but is a subjective opinion founded on experience.

Learned opinion is against the rule

Academic lawyers have commented unfavourably on the continued existence of the rule. It has been said to be wholly antithetical to the underlying justification for having expert witnesses, namely that ‘the drawing of inferences from the facts in question calls for an expertise which the tribunal of fact does not possess’.

The sort of quasi-existence of the rule brings its own problems. In R -v- Stockwell 8, the Court of Appeal accepted that if there was a rule prohibiting experts from giving an opinion on an ultimate issue, ‘... it has long been more honoured in the breach than the observance’. Indeed, in the light of recent case law, there can no longer be any doubt that an expert witness is able to give his opinion on an ‘ultimate issue’ in criminal proceedings, so long as that opinion is within the area of his expertise and the judge makes it clear that it is for the jury to decide the issue. In other words, the jury can hear the expert’s view but choose to ignore it.

The leading authorities on evidence, too, have suggested that the rule is effectively dead. Archbold (2004, 10–66, p.1287) states that:

‘... an expert is now permitted to give his opinion on what has been called ‘the ultimate issue’, but the judge should make it clear to the jury that they are not bound by the expert’s opinion, and that the issue is for them to decide’.

This is echoed in Keane on Evidence at pp. 507–508, which notes that:

‘... the prohibition against ultimate issue testimony has become largely irrelevant.’

The rule has, however, been a fairly tenacious one and is still capable of exerting some residual force. Mark Twain said, upon learning that his obituary had been published in the New York Journal, ‘... the reports of my death have been greatly exaggerated’. One is left to wonder whether the same might be said for the ultimate issue rule.


1 DPP -v- A and BC Chewing Gum [1967] 3 WLR 493 (DC)

2 National Justice Compania Naviera SA -v- Prudential Assurance Co Ltd (the Ikarian Reefer) [1993] 2 Lloyds Law Reports 68

3 Pride Valley Foods Ltd -v- Hall and Partners [2000] ABC LR 05/04

4 R -v- S:R -v- W [2006] EWCA Crim 1404

5 R -v- Gray [2003] EWCA Crim 1001

6 R -v- Mitchell [2005] EWCA Crim 731

7 R -v- Atkins [2009] EWCA Crim 1876

8 R -v- Stockwell [1993] 97 Cr App R 260



Issue 70
July 2011

In all likelihood
Experts and the ultimate issue
Conference notice

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June 2018

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