The first thing one observes when 'insanity ' and 'diminished responsibility' are juxtaposed to one another is that 'insanity' is extremely narrow in scope. It excludes any other form of mental aberration such as somnambulism, epilepsy, imbecility. The Scottish Law Commission suggests that it should be termed instead as "mental disorder" (1).
abnormality of the mind ( R v Byrne ); drug personality disorder (Celebici Trial); involuntary intoxication ( R v Galbraith) ; mental weakness and low intelligence ( Lord Dea's decision ) ; minority ( R v Raven ); physical deformities such as blindness and being a deaf-mute ( R v Pritchard). In the treatise "Partial Defences To Murder" more mitigating factors are added i.e. sufficient provocation by the offended party ( R v Smith ); immediate vindication of a grave offence to himself or his relatives (Table 7); Incomplete self-defence where there is no reasonable necessity of the means employed by the culprit (R v Martin); passion or obfuscation (Case 113); disease or injury (Note 17); jealousy, mercy killing, depression, relationship of victim to the accused (Table 7). The list goes on and on.
Insanity is a plea or defence by which the accused at the time of the commission of the act, "was laboring under such a defect of reason, arising from a disease of the mind, as not to know the nature and quality of the act he was doing or, if he did know it, that he did not know that what he was doing was wrong (The M'Naghten Rules). Insanity totally exempts the culprit from criminal liability unless he does it during a lucid interval. If so, he is wholly liable for the crime unless there are mitigating factors attending the crime.
Diminished Respons ...