A New Normal: Testing Cumulative Prospect Theory in Defendant Plea Decision-Making

Plea-bargaining is a common and necessary part of the American criminal justice system and though psycholegal scholars have made great advancements in our understanding of defendant plea behavior, the field generalcy lacks a sufficient theoretical model of plea-bargain decision-making. Across two experiments, this dissertation empirically tests Cumulative Prospect Theory (CPT; Tversky & Kahneman, 1992) as a potential model of defendant plea decisions. In Experiment 1, participants completed two risk aversion tasks, one economic and one adapted into a plea domain, to assess the presence of loss aversion and risk aversion in both domains. Findings suggest that, in a plea context, loss aversion may manifest in overweighting gains (rather than losses), significantly predicting plea decisions, Additionally, CPT outperformed SOT in all tests of predicting plea behavior. In Experiment 2, participants received a plea-bargaining vignette which manipulated guilt status, sentence type (probation vs. jail) and sentence magnitude (2 years vs. 11 years). Similar to Experiment 1, results from Experiment 2 suggest that CPT can better encapsulate plea decision-making than SOT, in part due to its ability to adjust for reference point and marginal utility. Overall, these experiments suggest that or understanding of defendant plea behavior improves when adapting a CPT framework. Future directions and implications for researchers are discussed.