R v Golds [2016] UKSC 61

Golds attacked his partner with a knife at their home, inflicting some 22 knife wounds together with blunt-impact internal injuries. He was tried for murder and relied on diminished responsibility under section 2 of the Homicide Act 1957, as amended. Expert psychiatric evidence was called about an abnormality of mental functioning, but the jury rejected the partial defence and convicted him. On appeal, Golds argued that the judge should have defined 'substantial' impairment and that any impairment beyond merely trivial was sufficient. The Court of Appeal dismissed the appeal but certified questions about the correct meaning of substantial impairment and whether judges must routinely define the term for juries. The Supreme Court considered the statutory language and earlier diminished-responsibility authorities.

What level of impairment counts as 'substantial' under section 2 of the Homicide Act 1957, and must a trial judge give the jury a detailed definition of that ordinary word?

The Supreme Court unanimously dismissed the appeal. 'Substantial' carries its ordinary meaning and denotes an impairment that is important or weighty. It is more than merely trivial or minimal, but the fact that an impairment crosses that low threshold does not necessarily make it substantial. The question is one of degree for the jury, considering the medical evidence and all the circumstances. A judge should not ordinarily burden the jury with elaborate synonyms. Where assistance is needed, the judge may explain that a substantial impairment lies between a merely trivial impairment and a total impairment, while stressing that the jury must make the evaluative judgment. The trial judge was not required to define the ordinary statutory word, and his direction disclosed no error.

For diminished responsibility, a substantial impairment of the relevant abilities means an impairment that is important or weighty, not merely one that is more than trivial. The assessment is a matter of degree for the jury, and the ordinary statutory word usually requires little judicial elaboration.

The case is the leading interpretation of the modern diminished-responsibility threshold in section 2 of the Homicide Act 1957 following amendment by the Coroners and Justice Act 2009. It rejects a formulation that would make almost any non-trivial impairment sufficient and preserves the jury's evaluative role. The defendant must still prove on the balance of probabilities an abnormality of mental functioning arising from a recognised medical condition, substantial impairment of a specified ability and an explanation for the killing. Success reduces murder to manslaughter; it does not provide a complete acquittal.