The application of the concept of multiple personality disorder (MPD) is one of the most complex and controversial issues facing forensic psychiatrists. The case presented is one in which a diagnosis of multiple personality disorder is not only well documented, but was so diagnosed at least 10 years before the ultimate homicide. Nonetheless, consideration of the legal issues was difficult. Other cases, particularly the Bianchi case, reflect the clinical difficulties in diagnosis. Subsequent cases have reflected a judicial review of the issues and a trend to disallow the concept of MPD as a defense; the author suggests that forensic psychiatrists incorporate these opinions in their future judgments.