The partial defence that reduces murder to voluntary manslaughter where an abnormality of mental functioning substantially impaired the defendant's responsibility for the killing.
A murder conviction carries a mandatory life sentence, so whether this defence succeeds can change everything that follows. This chapter begins with the nature and effect of diminished responsibility, the legislation governing it, the burden and standard of proof, and the four cumulative elements the defendant must establish. It then works through those elements: the abnormality of mental functioning arising from a recognised medical condition, the substantial impairment of the defendant's abilities, and the causal link between the abnormality and the killing. It closes with the trickier territory — how intoxication interacts with a recognised condition, the role of expert medical evidence, what remains a question for the jury, and how the defence differs from insanity.
