Abstract

There are legitimate worries about gaps between scientific evidence of brain states and function (for example, as evidenced by fMRI data) and legal criteria for determining criminal culpability. In this paper I argue that behavioral evidence of capacity, motive and intent appears easier for judges and juries to use for purposes of determining criminal liability because such evidence triggers the application of commonsense psychological (CSP) concepts that guide and structure criminal responsibility. In contrast, scientific evidence of neurological processes and function – such as evidence that the defendant has a large brain tumor – will not generally lead a judge or jury to directly infer anything that is relevant to the legal determination of criminal culpability . (Vincent 2008) In these cases, an expert witness will be required to indicate to the fact-finder what this evidence means with regard to mental capacity; and then another inference will have to be made from this possible lack of capacity to the legal criteria for guilt, cast in CSP terms.<br><br>To reliably link evidence of brain function and structure and assessment of criminal responsibility, we need to re-conceptualize the mental capacities necessary for responsibility, particularly those that are recognized as missing or compromised by the doctrines of “legal capacity” (Hart 1968) and “diminished capacity.” I argue that formulating these capacities as executive functions within the brain can provide this link. I further claim that it would be extremely useful to consider evidence of executive function as related to the diminished capacity doctrine at sentencing. This is because it is primarily at this stage in criminal proceedings where the use of the diminished capacity doctrine is most prevalent, as evidenced by the recent Supreme Court cases of Atkins v. Virginia (536 U.S. 304 (2002)) and Roper v. Simmons (543 U.S. 551 (2005)).<br>.