Importance of insanity has been reduced, mainly in murder due to the abolition of the death penalty and DR.
M'Naghten (1843).
D believed he was being persecuted by the Tories who were to blame for misfortunes. He intended to kill the prime minister himself but killed the secretary instead. Medical witnesses testified that he was insane. He was found not guilty on the grounds of insanity. A defence of insanity must follow the M'Naghten rules; D was under such a defect of reason, from a disease of the mind, as to not know the nature and quality of the act he was doing' and if he did know it, he did not know that it was wrong. .
Insanity can only be used for crimes that require mens rea.
DPP v H (1997) .
D charged with driving with excess alcohol- (strict liability). Magistrates acquitted him on the grounds that he was suffering from depression, a plea of insanity. The divisional courts held that the magistrates should have convicted.
Defect of reason.
It is not enough that D fails to use his powers of reasoning; his powers of reasoning must be impaired. .
Clarke (1972) (likely to come up in Unit 5).
D left without paying for goods she took form a supermarket. She claimed she did not have the mens rea of theft (intention to permanently deprive and dishonesty) because of absent-mindedness. Trial judge said this was a plea of insanity, at which point she pleaded guilty. On appeal her conviction was quashed by the divisional courts because she was not deprived of her powers of reasoning but simply failed to use them, therefore the trial judge was wrong. The lack of mens rea of Theft was the correct defence, i.e. no intention to permanently deprive and no dishonesty.
Disease of the mind.
This is a legal, not a medical term.
Kemp (1957) (likely to come up in Unit 4).
D made a motiveless attack on his wife with a hammer, for which he was charged with GBH. He was suffering from arteriosclerosis, where there is a congestion of blood on the brain.