Where expert evidence of a mental condition (such as dissociation from PTSD) is relevant both to a defence of insanity and to the separate question of whether a specific intent was formed, the trial judge's directions must make clear to the jury the relevance of that evidence to the intent question, not merely in the context of intoxication or the insanity defence. However, the proviso may apply where the expert opinion is based on scant evidence and is contradicted by abundant contemporaneous evidence of the accused's coherent and purposeful conduct.
The full text is available to signed-in members, including the 1 later case that cites this judgment.