Can Jurors Disregard Inadmissible Evidence? Testing Interventions Derived from Cognitive and Social Psychological Theories

For decades, researchers have found that jurors are consistently unable - or unwilling - to disregard inadmissible evidence when instructed to do so by a judge. The legal system ignores the problem entirely: judges have repeatedly affirmed that a judge’s instructions to disregard are a sufficient safeguard of defendants’ constitutional rights, regardless of whether the jury actually disregards the inadmissible evidence. This study tested four interventions derived from psychological research to identify the combination that most effectively helped jurors disregard inadmissible evidence (operationalized by lower conviction rates). It was hypothesized that the most effective interventions identified in Study 1 would yield significantly lower conviction rates when compared to traditional instructions to disregard in Study 2. The interventions were tested in Study 1 using Multiphase Optimization Strategy (MOST) methodology to identify the optimized intervention package through regression analysis. Study 2 served as a randomized controlled trial in which treatment as usual (a judge’s instructions to disregard) was compared to the optimized intervention package. Participants were randomly assigned to either (1) be exposed to no inadmissible evidence, (2) receive inadmissible evidence and treatment as usual, (3) receive inadmissible evidence, treatment as usual and the optimized intervention package, or (4) receive the inadmissible evidence without objection. Logistic regression revealed that jurors who were given an instruction to disregard produced lower conviction rates when they also received the optimized intervention package. Interpretation, limitations, and calls to action are discussed.