Genetics and Responsibility: To Know the Criminal from the Crime

Abstract

This article discusses the use of behavioral genetics in criminal cases and argues, contrary to the conventional view, that criminal responsibility theory limits the role behavioral predisposition testimony should play in assessing criminal responsibility. We proceed by reviewing criminal cases in which behavioral genetics and neurological evidence has been introduced - including claims that a defendant acted involuntarily, lacked the requisite mens rea, satisfied the mental defect element of an insanity defense, or was entitled to differential sentencing. This review reveals that courts have rejected the majority of these claims, but primarily because of the inadequacy of the science thereby leaving open the door for the introduction of such evidence in future criminal cases as the science further develops. The article then offers a more robust rationale for rejecting behavioral predisposition evidence when assessing a defendant's criminal responsibility. Using behavioral genetics as a tool, we explain why criminal responsibility theory clashes with defenses based on behavioral predispositions. We argue that the two components of criminal responsibility - liability and justifications and excuses to liability - operate with little regard to the infirmities of a criminal defendant. In so doing, we elucidate the fundamental characteristics underlying these components including the assumptions of legal free will and human agency, the voluntary act requirement, mens rea, and the reasonable person standard. We explain why seemingly anomalous defenses such as provocation and battered woman syndrome do not meaningfully challenge whether criminal responsibility operates without regard to a defendant's unique mental infirmities. Because liability and justifications and excuses to liability do not turn on individual infirmities, we conclude that behavioral genetics should not inform criminal responsibility.

Keywords: Criminal law, responsibility, genetics, behavioral genetics, behavioral predispositions, neurology, neuroscience, frontal lobe damage, addiction, actus reus, voluntary act, mens rea, insanity defense, mitigating evidence, aggravating evidence, sentencing, liability, justifications, excuses, reasonab