Demonstrations of a link between genetic variants and criminal behavior have stimulated increasing use of genetic evidence to reduce perceptions of defendants’ responsibility for criminal behavior and to mitigate punishment. However, because only limited data exist regarding the impact of such evidence on decision makers and the public at large, we recruited a representative sample of the U.S. adult population (n=960) for a web-based survey. Participants were presented with descriptions of three legal cases and were asked to: determine the length of incarceration for a convicted murderer; adjudicate an insanity defense; and decide whether a defendant should receive the death penalty. A fully crossed, between-participants, factorial design was used, varying the type of evidence (none, genetic, neuroimaging, both), heinousness of the crime, and past criminal record, with sentence or verdict as the primary outcome. Also assessed were participants’ apprehension of the defendant, belief in free will, political ideology, and genetic knowledge. Across all three cases, genetic evidence had no significant effects on outcomes. Neuroimaging data showed an inconsistent effect in one of the two cases in which it was introduced. In contrast, heinousness of the offense and past criminal record were strongly related to participants’ decisions. Moreover, participants’ beliefs about the controllability of criminal behavior and political orientations were significantly associated with their choices. Our findings suggest that neither hopes that genetic evidence will modify judgments of culpability and punishment nor fears about the impact of genetic evidence on decision makers are likely to come to fruition.

Background: Behavioral genetic research is beginning to elucidate some of the genetic contributions to human behaviors - including criminal and other problematic behaviors - and their interactions with environmental influences. One of the most studied of these interactions involves low-activity alleles of the monoamine oxidase A (MAOA) gene, which appear to increase the risk of antisocial behavior among males in the wake of childhood maltreatment. Some scholars have suggested that decisions about disposition of child abuse victims should be shaped by these findings, but the extent of public support for such approaches has not been assessed. Methods: In this study, a representative sample of the US population (n = 250) was presented with a vignette about a child, physically abused by his mother, who was tested for the presence of an allele that increases the risk of future impulsive violent behavior. Participants were asked about their views regarding the child's disposition, including return to his mother, and medical or psychological treatment. Results: Although participants thought that genetic data should be taken into account, the presence of an allele that increases the risk of impulsive violent behavior did not affect views regarding the child's return to his mother. However, it did increase respondents' willingness to provide the child with medical treatment and their view of the child as dangerous to other children. Conclusions: The findings suggest that behavioral genetic evidence has effects on perceptions of dangerousness and tendencies to view problems as medical but that the public is cautious about the use of genetic findings in child abuse adjudications.