Abstract
Legal “capacity” is a concept used by lawyers and mental health professionals working in the criminal justice system to either excuse their clients’ actions or mitigate punishment for committing illegal acts. This paper defines legal capacity, identifies its applications within the state and federal criminal justice arenas, and examines the impact mental health professionals and/or neuroscience has had, may have, or hopes to have in the near future on informing the courts precisely about defendants’ legal capacity. Legal capacity, which for terms of this paper is defined as the “ability to form a certain state of mind or motive, understand or evaluate one’s actions, or control them” (Clark v. Arizona, 2006, p. 749, n. 7), is discussed in terms of juveniles, the intellectually disabled, and the insane. In addition to discussing the Constitutional parameters and legal significance of capacity, the paper also discusses the mental health and neuroscience fields’ roles in helping to identify those who possess or lack the requisite legal capacity to commit crimes. The laws pertaining to each of these categories of defendants, i.e., juveniles, intellectually disabled, and, insane, are labyrinths with tangles of individual state and federal statutes and court decisions interpreting those statutes. The mental health and neuroscience research concerning these categories is still in its infancy and the maze of research has not produced a consensus. Moreover, it is unlikely that the states or courts will ever abdicate their responsibilities to decide these issues and leave such decisions to the mental health and neuroscience practitioners.