Insanity

The law recognises the mental state of the offender as important in a criminal defense. Criminal law holds people always accountable for their behavior, and responsible for a crime unless they have acted under severe and external duress (e.g. in self-defense, with a gun pointed at the head of the person) or they suffer a serious defect of rationality (e.g. being unable to distinguish right from wrong). The Model Penal Code (American Law Institute, 1962) requires the capacity for rationality: the defendant must be proved to have committed the crime whilst having a guilty state of mind. The physical elements that constitute a crime are called the actus reus (guilty act). The accompanied mental state is mens rea (guilty mind). Under the McNaughton Rule “every man is to be presumed to be sane”. To establish a defense on the ground of insanity, it must be clearly proved that, at the time of the crime, “the party accused was labouring under such a defect of reason, from disease of the mind, as not to know the nature and the quality of the act he was doing; or if he did know it, that he did not know he was doing what was wrong” (McNaughton Case, 1843).