Proceedings of the Annual Meeting of the Cognitive Science Society

Jurors operate as legal fact-finders, incorporating multiple pieces of evidence into their decisions. Prior work suggestsjurors may not be able to distinguish flaws in scientific evidence (Schweitzer & Saks, 2012) or properly assess the relia-bility of evidence (Thompson, 1989; Kaasa et al., 2007). However, it remains unclear how much probative value is givento individual evidence types. What prior weights do jurors place on different types of evidence and how do these predicttheir decisions? We built a Bayesian model of how people weigh individual pieces of evidence and used this to predictguilt ratings. Consistent with previous work, we found people have trouble distinguishing differences in quality amongevidence, and assign similar probative value to even flimsy types of evidence. The model also revealed individual weight-ing of evidence can exert large, and sometimes problematic effects on decisions to convict. We discuss the implications ofour findings for legal decision-making.