Inherited proclivity: When should neurogenetics mitigate moral culpability for purposes of sentencing?

Certain genes and neurobiology ('neurogenetics') may predispose some people to violent behavior. Increasingly, defendants introduce neurogenetic evidence as a mitigating factor during criminal sentencing. Identifying the cause of a criminal act, biological or otherwise, does not necessarily preclude moral or legal liability. However, valid scientific evidence of an inherited proclivity sometimes should be considered when evaluating whether a defendant is less morally culpable for a crime and perhaps less deserving of punishment. This Note proposes a two-pronged test to understand whether and when neurogenetic evidence should be considered to potentially mitigate an individual's culpability for criminal behavior. The first prong normatively assesses whether a defendant meets a threshold of having meaningfully managed his risk of harming others based on what he knew, or should have known, about his own proclivities to violence. The second prong considers the admissibility of the evidence based on whether the specific neurogenetic proclivity claimed by the defendant is relevant and adequately supported by science so as to be reliable. This proposed two-pronged test, beginning with an ethical threshold and followed by a scientific hurdle, can help judges and juries establish when to accept arguments for neurogenetic mitigation at sentencing, and when to reject them.