Courts increasingly use neuroscience and genetic evidence (neurogenetic evidence) to shed light on various aspects of a defendant's mental state and behavior. The evidence is particularly prevalent in cases involving defendants with mental illnesses and is used to determine issues of mental capacity, personal responsibility, and treatability. However, using neurogenetic evidence risks framing mental illness through a narrow explanatory model — one relying solely on biological causes. Such evidence elicits both stigma-reducing and stigma-enhancing implicit biases against mental illness, which can manifest themselves in beliefs that a person with mental illness is less blameworthy for his condition, but also more dangerous and less receptive to treatment. These implicit biases affect jurors (and potentially judges) and may influence sentencing decisions in cases involving defendants with mental illnesses, including ultimate sentencing decisions in capital cases.

While there has been vast literature on (1) the merging fields of neurogenetics and the law, (2) sentencing decisions in cases involving defendants with mental illnesses, and (3) implicit bias against mental illness, no article has connected the literature to provide an interdisciplinary account of these processes. This Note argues that the use of neurogenetic evidence in the courtroom may harm defendants with mental illnesses because the nature of the evidence primes negative implicit biases against mental illness. This Note then explores how this dynamic plays out during the sentencing phase in capital cases involving defendants with mental illnesses.