Lord Parker CJ observed at p165:
‘[W]ith the advance of science more and more inroads have been made into the old common law principles. Those who practise 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 any objection.’

Another case, like Clark, involving multiple sudden infant deaths.

Where expert opinion was seriously divided about the causes of the multiple infant deaths and there was no evidence other than the fact of the deaths to suggest murder, the prosecution should not be brought.

At C’s trial for murder, his counsel sought to adduce the report of a prison doctor to the effect that C had no mental disorder but had had no intention to kill. The judge’s decision to exclude the doctor’s report was upheld on appeal.

Where there was no evidence of any mental disorder and the defendant was entirely normal, there was no room for expert medical evidence on the defendant’s intent. That was a matter for the jury to decide.

Both her children having suffered cot deaths, the defendant was convicted of murder. Evidence suggesting that the deaths were natural was not disclosed and a leading paediatrician testified that the odds of two such deaths by accident was greater than those of tipping the Grand National winner four years in a row. The Court of Appeal overturned the conviction.

Although the appeal turned on non-disclosure of prosecution medical evidence the Court of Appeal expressed concern about the use of statistical evidence. Before admitting statistical generalizations in evidence, the court should examine the evidence carefully to make sure the jury are not misled. See also R v Cannings (2004), another case involving multiple cot deaths.

G’s wife was found hanging in the garage of the family home. He maintained she had committed suicide, but he was convicted of her murder. On appeal he sought to adduce expert psychiatric evidence to cast light on the deceased’s state of mind. The court refused to admit the evidence.

An expert’s opinion was admissible to provide the court with scientific information that was likely to be outside the jury’s experience. But the jury could form an opinion unaided on the proven facts. Expert evidence of how someone’s mind operated at the time of an offence was inadmissible unless there was an issue of insanity or diminished responsibility.

The appellants (H, B, and O) in joined cases involving shaken baby syndrome, appealed against their convictions for manslaughter, causing grievous bodily harm, and cruelty; and for murder. They sought to adduce new expert medical evidence.
B’s conviction was overturned based on the new evidence but the other convictions were held to be safe.

The Court of Appeal gave detailed case management guidance for situations where expert evidence was the only evidence of guilt. The evidence should be properly organised before it is presented to them. The problem for the court was how to manage expert evidence so that a jury could be directed in a way which would, so far as possible, ensure that any verdict they reached was justified on a logical basis.

At his trial for drug dealing, a police officer was allowed to give evidence that the quantity of drugs found was more than would be required for H’s own use—allowing the jury to infer that he was a dealer. The admission of the police officer’s evidence was upheld on appeal.

An experienced police officer could act as an expert witness, particularly as he could be cross-examined and evidence could be called to rebut his evidence.

Two men were accused of murdering a girl. Each maintained that the other had done the killing. L’s co-defendant called a psychiatrist to give evidence that L’s personality made it more likely he was the killer. The Privy Council held the evidence had been rightly admitted.

The psychiatrist’s evidence was relevant to show that the co-defendant’s version of the facts was more likely than L’s and to negative L’s case. This is an exception to the usual rule that expert evidence is not admissible on matters for which the jury requires no assistance.

The appellants were convicted of cruelty to their foster children. Evidence was admitted from a counsellor of one of the victims (RP), supporting factually the chronology of the reporting of the history of the abuse. In the summing up the prosecution claimed RP was an expert witness, although this had not been claimed in the trial proceedings. The defendants appealed.

The prosecution was wrong in the claim, although the conviction was upheld, RP’s evidence went to fact. The Court held that only rarely would expert evidence from a counsellor be relevant or admissible but it did not pronounce on the nature of counselling expertise.

T admitted having killed his girlfriend; but claimed he had been provoked by her saying he was not the father of her expected child. He sought to call a psychiatrist to say that he was not violent by nature but that his personality was such that he could have been provoked in the circumstances and that he was likely to be telling the truth. The Court of Appeal upheld the exclusion of the psychiatric evidence.

The evidence was irrelevant because T’s mental health was not in issue. There was no general rule that psychiatric evidence was admissible to prove that a defendant was likely to be telling the truth. His veracity and the likelihood of his being provoked were matters for the jury.