PHILOSOPHICAL PRESUPPOSITIONS OF THE DEFENSE OF INSANITY IN ANGLO-AMERICAN LAW: THE FORMULATION, JUSTIFICATION, AND MEANING OF LEGAL INSANIT

The legal defense of insanity raises questions about the nature of moral responsibility and the justification for the imposition of punishment for violation of the criminal law. Punishment involves blame and condemnation and, in turn, presupposes that those subject to its imposition are capable of responsible action.;Through the influence of canon law and rediscovered Roman law sources, the excuse of insanity came to be recognized by the twelfth century. A lack of understanding was central to this excuse which denied capacity for responsible action. The impairment of understanding was traced through the will. The defense provided that a person was not culpable if he lacked capacity for conforming conduct. By the middle of the nineteenth century, the defense was formulated in terms of a capacity to know right from wrong or know the nature of one's action.;Underlying the insanity defense is a conept of voluntariness which distinguishes action from mere movement. More fundamentally, where punishment is properly understood as imposition of deprivation accompanied by condemnation, it is necessary to show that the subject is responsible in order to be properly regarded as blameworthy. This is in turn requires that an agent be capable of free choice, in terms of being able to act otherwise. Such a concept of free choice implies a capacity for self control.;Punishment is imposed by the legal system for the commission of crimes. Punishment implies blame. A criminal violation involves a moral breach in that it consists of action which violates norms established for the protection of society or realization of social goals. Such a violation consists of three elements relevant to the establishment of responsibility: act, defined mental state, and a general capacity for conforming behavior. The first two elements are specified in a positive manner and may be defeated by a showing of mental illness; the third requirement involves a presumption of responsibility which is negated by a recognized excuse such as legal insanity.;A formulation of the legal defense of insanity should be consistent with a view of man as rational; consistent with a concept of integration human personality; require a determination of the existence and effect of mental disease on the understanding and the volitional phase of personality. A formulation which satisfies these criteria can be stated in the following terms: The Legal Defense of Insanity is established when it is shown that a person, accused of a crime, is suffering from a mental disease as the result of which his understanding is so impaired that he lacks the capacity for conforming conduct. Such impairment of understanding is established when it is shown that an accused lacked the capacity to appreciate the physical nature and consequences of his act, or lacked the capacity to appreciate that it was morally wrong to commit the act in question.;Without the legal defense of insanity, the criminal law would be deprived of an essential instrument for determining those who are properly subject to its jurisdiction. There is an absolutely crucial distinction between the individual who has freely and knowingly undertaken to inflict violence or harm on another person, and the individual who has brought about exactly identical harmful consequences while being in the grip of mental conditions which preclude appreciation and control of his action. The legal defense of insanity captures this critical distinction. Ultimately principles of fairness and morality lie at the foundation of the legal defense of insanity, and are its final justification.