Scientific evidence is increasingly being presented in criminal courts to explain criminal behavior. While psychological evaluations have long been part of the criminal sentencing process, more recently attorneys have also begun presenting evidence on defendants' genetics or on innate mental disorders, with mixed results on sentencing outcomes. This study examines how judges assess and understand scientific evidence during sentencing decision-making. We interviewed 34 judges that have presided over criminal cases and asked them to make sentencing decisions for fictional defendants that suffered from either a genetic or an acquired brain disorder. We further asked judges to rate the importance of various legal concepts and standards in cases where defendants put forward scientific evidence to explain their behavior. Interviews were analyzed using both quantitative and qualitative methods. The results of this study provide unique insights into the ways in which judges assess and decide cases when they are presented with scientific information to explain defendants' behavior. We propose several ways forward that may help better integrate biology and genetics research into the criminal justice process.
