Defences become relevant when the actus reus of an offence has been committed with the aplicable mens rea.
The defence of insanity is too narrow to inclue menay of the mental problems from which people can suffer - this is why the Homicide Act 1957 introduced the partial defence of diminished responsibility. The verdict given when a person successfully pleads insanity is 'not guilty by insanity'.
The defence of automatism requires an external factor - which distinguishes is from insanity. However the defence will not be available if the defendant was responsibile for ceating the automatism.
The defence of intoxication is sometimes said not to be a defence at all, but the incapacity to form the mens rea of the crime. A defendant will be committed whilst intoxicated, but being drunk or under the influence of drugs may mean that the necessary intent could not be formed for crimes such as murder.
Self defence/prvention of crime are a mixture of defences that largely apply to crimes involving violence.
The defence of insanity:
D must prove on balance of probabilities that hee was insane at the time of the offence
'not guity by defence of insanity'
M'Naghten test - defect of reason, diease of mind, D doesnt know natue or wuality of his act or does not know that what he was doing was wrong.
Defect of reason - inability to use power of reason - Clarke - absent mindness isn't insanity
Caused by disease of the mind - legal term not medical one. mus be a physcial disease (internal) not brought on by an external factor - can be a permanent or temporary state. Kemp - arteriosclerosis caused occasional lapses - killed his wife during which and was treated as insanity. Bratty - phsychomotor epileptic it can ammount to insanity rather than automatism - automatism requires external factor. Burgees - sleepwalking can be a disease of the mind if caused by internal factor.
D doesn't know quality of his act/what he was doing was wrong - didn't know what he was doing, didn't appreciate consequences, didn't appreciate circumstances.Windle - D didi know the nature and quality of his act and what he was doing was wrong so couldn't plead insanity.
The defence of automatism:
D needs to show that his act was…