Criminal Law In Daryl Derek Richardson v R [2026] EWCA Crim 1131, handed down on 28 August 2026, the Court of Appeal (Criminal Division) refused an application for leave to appeal against a murder conviction arising from the fatal stabbing of Muhammed Jassey in Brighton in April 2020. Richardson had been convicted alongside a co-defendant, Bobby Smith, following a trial at Lewes Crown Court, and was sentenced to life imprisonment with a minimum term of just under 25 years. His case on appeal rested squarely on psychological and psychiatric evidence that had not been before the jury.
A chartered clinical psychologist, Dr Alexandra Antonesei, had assessed Richardson using the Wechsler Adult Intelligence Scale, finding an average full-scale IQ of 105 but a Verbal Comprehension Index at only the 7th percentile, alongside a diagnosis of severe ADHD. A consultant forensic psychiatrist, Dr Philip Huckle, gave supporting evidence directed at diminished responsibility. Richardson argued that this evidence should have prompted the appointment of an intermediary at trial, and that the jury should have heard how his cognitive profile bore on his decision not to give evidence and on his culpability generally.
The Court rejected every ground. It held that diminished responsibility could not assist a defendant whose case at trial was that he had played no active role in the stabbing at all — the defence requires evidence about how a defendant’s mental processes affected his own conduct, and Richardson had never advanced an account of his conduct capable of being explained by impairment. For the same reason, the ADHD evidence could not have assisted the jury: as the Court put it, they “could not have been assisted by any evidence about ADHD and its effects on Mr Richardson” when his defence was that he had nothing to do with the stabbing itself. The Court also found that experienced leading counsel had already given him clear, accessible advice about testifying, so no intermediary was required either at trial or, retrospectively, on appeal.
For psychologists and psychiatrists instructed in criminal appeals, the judgment is a clean illustration of a recurring trap: an otherwise credible cognitive or psychiatric assessment cannot repair a case theory it was never designed to support. Expert evidence on impairment only assists where the defendant’s own account leaves room for it — a point worth flagging to instructing solicitors before, not after, the report is commissioned.
