Katrina Sifferd, William Hirstein, and Tyler Fagan
Under review to be included in The Insanity Defense: Multidisciplinary Views on Its History, Trends, and Controversies (Mark D. White, Ed.) Praeger (expected Nov. 2016)
1. The cognitive capacities relevant to legal insanity
Legal insanity is a legal concept rather than a medical one. This may seem an obvious point, but it is worth reflecting on the divergent purposes and motivations for legal, as opposed to medical, concepts. Medical categories of disease are shaped by the medical professions’ aims of understanding, diagnosing, and treating illness. Categories of legal excuse, on the other hand, serve the aims of determining criminal guilt and punishment.
A theory of legal responsibility and its criteria should exhibit symmetry between the capacities it posits as necessary for moral, and more specifically, legal agency, and the capacities that, when dysfunctional or compromised, qualify a defendant for an excuse. To put this point more strongly, the capacities necessary for legal agency should necessarily disqualify one from legal culpability when sufficiently compromised. Thus one’s view of legal insanity ought to reflect whatever one thinks are the overall purposes of the criminal law. If the purpose of criminal punishment is social order, then legal agency entails the capacity to be law-abiding such that one does not undermine the social order. If the purpose is institutionalized moral blame for wrongful acts, then legal agency entails the capacities for moral agency. If a criminal code embraces a hybrid theory of criminal law, then all of these capacities are relevant to legal agency.
In this chapter we will argue that the capacities necessary to moral and legal agency can be understood as executive functions in the brain.
The chapter is here.