Diminished responsibility in English law

In English law, diminished responsibility is one of the partial defences that reduce the offence from murder to manslaughter if successful (termed "voluntary" manslaughter for these purposes). This allows the judge sentencing discretion, e.g. to impose a hospital order under section 37 of the Mental Health Act 1983 to ensure treatment rather than punishment in appropriate cases. Thus, when the actus reus (Latin for "guilty act") of death is accompanied by an objective or constructive version of mens rea (Latin for "guilty mind"), the subjective evidence that the defendant did intend to kill or cause grievous bodily harm because of a mental incapacity will partially excuse his conduct. Under s.2(2) of the Homicide Act 1957 the burden of proof is on the defendant to the balance of probabilities. The M'Naghten Rules lack a volitional limb of "irresistible impulse"; diminished responsibility is the volitional mental condition defence in English criminal law.

Section 2 of the Homicide Act 1957 states: (1) Where a person kills or is party to a killing of another, he shall not be convicted of murder if he was suffering from an abnormality of mental functioning which -

(1A) Those things are -

(1B) For the purposes of subsection (1)(c), an abnormality of mental functioning provides and explanation of D's conduct if it causes, or is a significant contributory factor in causing, D to carry out that conduct.

The defence has recently been amended by s. 52 of the Coroners and Justice Act 2009, which came into force on 4 October 2010.

R v Golds provides a recent authority from the Court of Appeal Criminal Division on how the courts will interpret the term 'substantial'. At paragraph [55] of Elias LJ's judgment (following the paragraphing from the neutral citation given below) two senses of the word 'substantial' are identified: (i) something substantial is more than something which is merely trivial or minimal owing to the fact that it has "substance", or (ii) something substantial is big or large (e.g. in the sense that a substantial salary is a large one). At paragraph [72] Elias LJ concludes by opining that the court should (i) leave interpretation of the word 'substantial' to the jury, but if asked for further help should (ii) direct them under the second meaning of the term (i.e. substantial meaning big).

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