Are Mock-Jurors Sensitive to the Benefits of Collective Decision-Making?

Abstract

Jurors are often presented with forensic expert testimony and tasked with understanding and making decisions about the evidence. Collective decision-making such as blind verification is used due to the benefits of aggregating independent decisions to increase accuracy and reduce potential biases. The current study is the first to investigate how mock jurors interpret the credibility of collective decision-making evidence. We used a 2x4 between-subjects factorial design to test if the number of experts or the independence of their decision affects mock jurors’ credibility ratings of the testimony. It was predicted that credibility ratings would increase with group size for both groups, but the independent group would be rated higher in credibility. A student sample and an experienced jury sample were collected to test if this had any effect on the results, then an exploratory meta-analysis was run with the combined sample. Generalised linear models with polynomial contrasts found no significant effects for independence, while only the combined sample showed a significant effect for crowd size on credibility ratings. Results suggest that mock jurors are not sensitive to the benefits of independence in collective decision-making, while they may be sensitive to the number of experts. Further research is required to understand the relationship between these variables and credibility ratings. The use of collective decision-making in forensic science may need to be used with caution if jurors are not as sensitive to the increases and decreases in accuracy that come with collective decision-making as expected.