Unqualified Acquittal versus Insanity: Mental Disorder as an Evidentiary Issue, Not an Affirmative Defense

Abstract

Although the insanity defense has been present in our criminal justice system for centuries, this paper discusses the utility of the defense as compared with that of an evidentiary attack on the mental elements of the crime itself. By reviewing insanity acquittal data and analyzing the substantive insanity defense and rules of evidence along with the progeny case law, we conclude that the insanity defense does not always provide the greater criminal defense option when mental health is in issue. There exists what this article refers to as “element negation,” which enables a criminal defendant to achieve complete acquittal based on a lack of the requisite mens rea in any charged crime. Because element negation is a viable defense to any crime, and it encompasses any evidence that would be used to proffer an insanity argument, mental disorder as evidence can be governed by the rules of criminal procedure and evidence, which may render the affirmative insanity defense a less appealing option.