R v Marvin Samuels

For diminished responsibility, a diagnosis of a recognised medical condition is insufficient by itself. The defence must prove, on the balance of probabilities, that an abnormality of mental functioning substantially impaired at least one statutory capacity and caused or significantly contributed to the killing. The jury must assess all the evidence, including the defendant’s conduct, rather than expert opinion alone.

Fresh expert evidence on appeal is admitted only where the interests of justice make it necessary or expedient. A later opinion based on longer observation may be admissible, but a repetition or near-repetition of trial evidence will rarely justify reopening a conviction. Evidence which cannot realistically undermine the safety of the conviction affords no ground for appeal.

The applicant was convicted at the Central Criminal Court in 2013 of murdering Sharlana Diedrick. He had pleaded guilty to rape and causing grievous bodily harm with intent against another woman, referred to as V. He was sentenced to life imprisonment, with a minimum term of 33 years for murder.

Nearly a decade later, he sought an extension of time and leave to appeal against conviction and sentence. He relied on fresh psychiatric evidence from Dr Murray, who diagnosed paranoid schizophrenia and disputed the earlier diagnosis of antisocial personality disorder. The Crown relied on evidence from Dr Blackwood. The central issues were whether the fresh evidence should be admitted under the Criminal Appeal Act 1968 and whether it could render the murder conviction unsafe.

The applications were refused. The court declined to receive the proposed fresh evidence, refused an extension of time, refused leave to appeal against conviction, and held that the application concerning sentence therefore fell away.

1. Under section 2 of the Homicide Act 1957, the defence had to prove that an abnormality of mental functioning arose from a recognised medical condition, substantially impaired one or more statutory capacities, and caused or significantly contributed to the killing. A diagnosis of paranoid schizophrenia, or exclusion of a personality disorder, would not by itself establish diminished responsibility.
2. The power under section 23 of the Criminal Appeal Act 1968 is wide and must be exercised in the interests of justice. The court accepted that Dr Murray’s evidence was capable of belief, would have been admissible at trial, and had at least a strongly arguable explanation for not having been called earlier. However, it did not consider that the evidence might afford a ground for allowing the appeal.
3. The principle in R v Kai-Whitewind [2005] EWCA Crim 1092 applied. Fresh expert evidence which merely adds another opinion on an issue already considered at trial will rarely justify reopening the case, particularly given the public interest in finality. R v Petrolini [2012] EWCA Crim 2055 recognised that later observation may permit a clearer assessment, but the facts there were materially different.
4. The later period of observation occurred in a closely controlled hospital environment, and Dr Murray relied significantly on the applicant’s changing accounts. The court was not persuaded that his opinion could displace the assessments of three psychiatrists who had examined the applicant shortly after the killing. In any event, the jury had to consider all the evidence, including the attacks on V, the applicant’s preparation before meeting Ms Diedrick, and his conduct during and after the killing. There was compelling evidence that any abnormality did not substantially impair his understanding, rational judgment or self-control.

• Court of Appeal (Criminal Division): On 27 July 2023, after referral by the single judge, the full court refused to receive fresh evidence, refused an extension of time and refused leave to appeal against conviction under Criminal Appeal Act 1968.
• Central Criminal Court: In 2013, the applicant was convicted of murder after trial, having pleaded guilty to rape and causing grievous bodily harm with intent. He received life sentences, including a minimum term of 33 years for murder.