Dissociation and the insanity defense: A review of U.S. Federal appellate case law

Pathological dissociation is relatively common in the United States and may be associated with violent or criminal behavior. Dissociative Disorders, especially Dissociative Identity Disorder, are considered controversial diagnoses by some in the psychiatric and legal professions. Individuals who offend during dissociative states may not be criminally responsible if they meet the legal standard for insanity, however, insanity pleas based on dissociative symptoms are rare. This review examined Federal appellate case law for potential legal barriers to the insanity defense for dissociative conditions and any restrictions imposed on related expert evidence. Few rulings directly addressed these questions but there do not appear to be any unique barriers for dissociation-related insanity pleas. Some cases provided valuable insights regarding the admission of expert evidence, effective expert testimony, and the role of defense counsel.