16 The Neurobiology of Individual Decision Making , Dualism , and Legal Accountability

Over the course of the last decade there has been an increasing interest in neurobiological analyses of the causes of behavior among many practitioners of criminal law. In some institutional circles this has crystallized as an interest in providing a physical method for classifying the actions of human agents according to preexisting social–legal categories. The impetus driving this search for neurobiological classifi cation tools stems from both the longstanding Western legal requirement that actors be held accountable only for those voluntary actions which are preceded by what is termed a culpable mental state (those for which mens rea can be established) and the longstanding legal diffi culty in establishing culpable mental state at trial. Thus a pressing question for many legal practitioners is whether existing neurobiological techniques or data can be used to identify the socially defi ned categories that guide law and punishment. If neurobiological measurements did suggest a division of the physical causes of behavior into biological categories closely aligned with social categories, then neuroscience might indeed be very useful for making this legal distinction. In contrast, if neurobiological data suggested that (at a physical rather than a social level) no fundamental division of behavior into these categories could be supported, then we would face a social dilemma of sorts. We would have to decide whether the social consensus that supports differentially