Moral Foundations and Prejudicial Evidence: Helping Jurors Adhere to Jury Instructions

Across three studies and two robust pilot studies, this project addressed issues surrounding prejudicial evidence and jury instructions to disregard inadmissible evidence. Specifically, this project examined a new framework for understanding how people vary in their response to prejudicial evidence, based on the morals they value, and tested the effectiveness of a novel way to phrase jury instructions to debias jurors inspired by moral foundations theory. In two experimental studies, participants read a transcript of a sexual assault (Study 1: n = 544) or an assault and battery criminal case (Study 2: n = 509). In each experiment, participants were randomly assigned to read either a case with or without prejudicial evidence. Participants exposed to prejudicial evidence were either given standard jury instructions to disregard the evidence, no instructions, or novel jury instructions inspired by moral foundations theory. Individual differences in moral foundations affected how susceptible people were to prejudicial evidence and case facts in general. This pattern emerged regardless of the type of jury instructions in most cases, suggesting that the moral foundation inspired instructions failed to help jurors disregard prejudicial evidence. The impact of people’s moral foundation endorsement has direct implications for how attorneys may phrase evidence to cater towards these moral biases and select ideal jurors during the voir dire process. To further advance people’s understanding of the effects of prejudicial evidence and jury instructions in legal settings, a third study looked at how attorneys (n = 138) perceived the prevalence and impact of prejudicial evidence in real cases and the effectiveness of jury instructions. Over three quarters of the sample (77.54%) reported having experienced prejudicial evidence in their cases and expressed concern that prejudicial evidence is influential to jurors with jury instructions being ineffective. Taken altogether, the results of this project show the potential impact moral foundation endorsement can have on case judgments and how jurors are differently influenced by prejudicial evidence. In addition, data from attorneys showing the perceived prevalent and impact of prejudicial evidence in real cases further justifies the need to continue researching safeguards against prejudicial evidence.