Empirical Research on the Insanity Defense

In contrast to the jurisprudential history of the insanity defense, significant empirical research on its use and effects has emerged only in the past decade. The research is organized here around six major questions closely related to the public policy questions that have gained much currency in the wake of the John Hinckley trial. In many instances, the research data sharply conflict with popular notions of who are acquitted by reason of insanity and how long they are hospitalized after acquittal. There is considerable consistency across jurisdictions on the characteristics of acquittees and their recidivism rates, but substantial differences on the length of their detention both across jurisdictions and in different time periods within jurisdictions. Future research, to be productive for both policy and substantive purposes, requires multistate designs with a systemic approach.