R v Gavin Lee McNaughton

Where the prosecution invites a jury to infer a causal connection between alleged conduct and a medical condition outside ordinary knowledge, it must provide a credible forensic foundation, ordinarily through expert evidence. A judge must not invite jurors to supply specialist knowledge, speculate about causation, or express a non-expert personal view.

In summing up, a judge may fairly comment on evidence that assists or undermines either case. The judge must nevertheless remain, and be seen to remain, impartial. Directions that the facts are for the jury do not cure comments that trespass on the jury’s fact-finding role or appear to advocate for the prosecution.

The appellant was convicted at the Crown Court at Norwich of historical sexual offences concerning a child with whom he lived. He accepted limited vaginal touching during an earlier period but denied digital penetration and the more extensive conduct alleged.

The complainant and her mother gave evidence that the complainant had recurrent thrush and a sore, red vagina. No medical expert gave evidence about the condition, its incidence, or its possible causes, although the prosecution held medical records. In summing up, the judge invited the jury to consider whether a seven-year-old could have severe and recurrent thrush and whether digital penetration was the likely cause.

The appeal concerned whether those comments, and the absence of a proper evidential basis for the causal inference, rendered the convictions unsafe.

1. The appeal against conviction was allowed. The convictions after trial on counts 2 to 4 were unsafe, were quashed, and a retrial was ordered.

2. The suggested connection between recurrent thrush and digital penetration required expert evidence if the prosecution wished to rely on it. There was no credible forensic foundation for the jury to infer causation. The judge’s questions instead invited jurors to assume medical expertise that was not common knowledge, or to speculate. The correct direction was that no causal conclusion could legitimately be drawn from that evidence.

3. The court applied the impartiality principles reviewed in R v L [2020] EWCA Crim 332, Reynolds [2019] EWCA Crim 2145, and Haddon [2020] EWCA Crim 887. A judge may comment on the evidence and need not redress a weak case or reduce a strong one. However, the judge must remain above the fray, must not take factual conclusions from the jury, and must not express a view that appears to advocate for the prosecution. A general instruction that facts are for the jury does not necessarily cure such a defect.

4. The present case was not merely a case of partial summing-up of the kind considered in Digby [2020] EWCA Crim 1815. The jury had no proper evidential basis for the inference in the first place. Further, the summing-up presented digital penetration as the likely explanation for the condition without a balanced evidential basis. The resulting taint extended to all the trial convictions.

5. Despite the time already served, the seriousness of the allegations and the remaining admissible evidence made a retrial in the public interest. The court ordered a fresh indictment under CrimPR 10.8(2), re-arraignment within the specified period, determination of venue by the presiding judge, and the appellant’s release on bail. The appeal against sentence relating to the plea was adjourned.

• Court of Appeal (Criminal Division) — allowed the appeal against conviction, quashed the trial convictions on counts 2 to 4, and ordered a retrial: [2024] EWCA Crim 1129. The appeal against sentence relating to the plea was adjourned.

• Crown Court at Norwich — the appellant was convicted on 24 August 2023 of the historical sexual offences tried before His Honour Judge Shaw and received a total sentence of 28 months’ imprisonment.