How substantial must the impairment be?

R v Golds^[2] 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).

Diminished responsibility and voluntary intoxication

Voluntary intoxication will not satisfy the criterion that there must be an abnormality of mental functioning arising from a recognised medical condition (s.2(1)(a) Homicide Act 1957) and therefore cannot be relied upon as grounds for the partial defence.^[3] However a person suffering from alcoholism that has led to an abnormality of mental function may have access to the partial defence.^[4] In R v Gittens^[5] a defendant who suffered from depression killed his wife and stepdaughter after drinking and taking drugs for medication. The direction to a jury facing both diminished responsibility and drunkenness should be:

• Would the defendant have killed as he did if he had not been drunk?

and if the answer to that is yes,

• Was he suffering from diminished responsibility when he did so?

The more chronic forms of alcoholism and the long-term use of heroin and cocaine (see R v Sanderson^[6]) can become a relevant factor where a craving for drink or drugs causes an abnormality of mind. This must be distinguished from the situation in which the abnormality of mind causes a craving for drink or drugs . R v Tandy^[7] held that where a defendant could show that she was suffering from an abnormality of the mind, that it was induced by disease (namely alcoholism), and that it substantially impaired her responsibility for her actions, then the defence of diminished responsibility would be made out. In the actual case, the craving for alcohol did not render the use of alcohol involuntary. The defendant was in control when she began drinking, and the state of mind in which she killed her daughter was merely induced by the alcohol. In R v Dietschmann,^[8] the House of Lords held that where a defendant suffers from an abnormality of mind within s2(1) also consumes alcohol before the killing, the jury should find him or her guilty of manslaughter if they are satisfied that, notwithstanding the alcohol consumed and its effect, the abnormality of mind substantially impaired the mental responsibility for the fatal acts. The sub-section does not require the abnormality of mind to be the sole cause of the defendant’s acts; even if the defendant would not have killed if he had not consumed alcohol, the causative effect of the alcohol does not prevent an abnormality of mind suffered by the defendant from substantially impairing his mental responsibility for the fatal acts. Dietschmann was later applied by the Court of Appeal in R v Hendy.^[9]