The mental disability requirement in the insanity defense

This paper offers a discussion of some of the nuances of mental disease or defect as required for the insanity defense in criminal law. It also compares and contrasts the mental disease or defect definitions of criminal law with those definitions used in clinical practice. It points out a general pattern of vagueness and dispute regarding the proper interpretation of the mental disability requirement in the insanity defense and in other legal provisions. It reports a variety of interpretations by courts and commentators regarding the meaning of these phrases, and it reports attempts by state legislatures to narrow the range of applicable conditions by excluding various mental or emotional states.