The insanity defense1 is deeply rooted in Anglo-American law. Although the specific standard by which legal insanity is determined has varied over time and across jurisdictions, the insanity defense has always been grounded in the belief that there are defendants whose mental conditions are so impaired at the time of the crime that it would be unfair to punish them for their acts.
Recognizing that the insanity defense plays a critical role in the administration of criminal justice in the United States, the American Psychiatric Association endorses the following positions:
1) Serious mental disorders2 can substantially impair an individual’s capacities to reason rationally and to inhibit behavior that violates the law. The APA strongly supports the insanity defense because it offers our criminal justice system a mechanism for recognizing the unfairness of punishing persons who exhibit substantial impairment of mental function at the time of their actions.
2) The APA does not favor any particular legal standard for the insanity defense over another, so long as the standard is broad enough to allow meaningful consideration of the impact of serious mental disorders on individual culpability.
1By the term “insanity defense,” we include verdicts of “not guilty by reason of insanity,” “guilty but not criminally responsible,” and related formulations.
2“Serious mental disorder” is meant to encompass not only major psychiatric disorders, but also developmental disabilities and other causes of impaired mental function (e.g., severe head trauma) that otherwise meet the legal criteria for the insanity defense.