The Insanity Defense: Five Years of Research (1993–1997)

Abstract

One of the fundamental presumptions of our criminal justice system is that legal responsibility entails both actus reus and mens rea ; that is, to be held criminally responsible a person must have freely chosen to commit a criminal act, knowing that this act was criminal. As the presence of a mental disorder is seen by some as rendering a person unable to form criminal intent, the insanity defense was instituted, with the effect of offering mentally disordered persons potential exemption from criminal responsibility. However, because the insanity defense “purports to draw a line between those who are morally responsible and those who are not, those who are blameworthy and those who are not, those who have free will and those who do not, those who should be punished and those who should not” (Stone, 1975, p. 218), it has been subject to more debate and criticism than any other criminal law (e.g., Perlin, 1996). Surprisingly, despite the fact that these controversies have been played out extensively in philosophical and theoretical debates, empirical research on the insanity defense is relatively limited in quantity. The present article reviews research on the insanity defense in the 5-year period spanning 1993 to 1997. Publications used in this review were obtained through a search of Psychinfo and MedLine. An initial review of abstracts was undertaken by the first author to exclude any of the literature that did not include empirical data. 1 No effort was made to search for relevant articles in legal periodicals, nor was any effort made to obtain translations of articles published in languages other than English. In addition, some articles were later excluded, as they included the insanity defense only at the most peripheral