The influence of genetic information and crime-type on juror decision making

The Monoamine Oxidase A (MAOA) gene, paired with a traumatic childhood background, can predispose an individual to behave impulsively and aggressively. Defence lawyers see this genetic link as a way to reduce a defendant's sentence. This study endeavoured to establish whether mock jurors see this evidence as grounds for reducing a sentence, or, as the literature indicates, likely to increase it, on the basis of dangerousness. The influence of genetic evidence on crime-type differences (i.e., assault compared to bank fraud) was also investigated. A total of 217 participants (148 females) between 18‚Äö-75 years of age (M = 31.35, SD = 14.18) were randomly allocated to one of four conditions detailing a crime (white-collar or blue-collar) and additional expert evidence regarding the possession of the MAOA gene (with a control group). Participants, acting as mock jurors, completed questions regarding judgements of the defendant's level of culpability, level of dangerousness, and how severe the sentence should be. Findings demonstrated that mock jurors who received additional genetic evidence viewed the defendant as less culpable for the crime and more dangerous, but overall, provided a less harsh sentence than those who were not presented with such evidence. Crime-type differences were found only for perceptions of dangerousness, showing that blue-collar criminals with the MAOA gene were seen as more dangerous than white-collar criminals with the gene. These findings suggest that while perceptions of dangerousness are heightened, jurors believe a mitigated sentence is warranted for a defendant who possesses the MAOA gene. This has implications for defence lawyers who can utilise this form of evidence to mitigate their defendants' sentences.