Developing a Model of Guilty Plea Decision-Making: Fuzzy-Trace Theory, Gist, and Categorical Boundaries

Objectives: To date, most research on plea bargaining has used some form of the shadow of the trial (SOT) model to frame defendant decisions. In this research, we proposed and tested a new conceptual model of plea decision-making, based on fuzzy-trace theory (FTT), for the context in which a nondetained, guilty defendant chooses between a guilty plea or trial, where both the plea and potential trial sentence entail incarceration. Hypotheses: We predicted that plea decisions would be affected by (a) meaningful, categorical changes in conviction probability (e.g., low to moderate, moderate to high), as opposed to more granular changes within categories and (b) the presence and magnitude of categorical distinctions between plea offer and potential trial sentence rather than fine-grained differences between individual offers. Method: We conducted three vignette-based experiments (Study 1: N = 1,701, Study 2: N = 1,098, Study 3: N = 1,232), using Mechanical Turk participants. In Studies 1 and 2, we manipulated potential trial sentence and conviction probability, asking participants to indicate either the maximum plea sentence they would accept (Study 1) or whether they would plead guilty to a specific offer (Study 2). In Study 3, we manipulated plea discount and potential trial sentence and measured plea acceptance. Results: Maximum acceptable plea sentences were similar within and different between "groupings" of meaningfully similar conviction probabilities (Study 1). Plea rates were similar within and different between groupings that comprised plea offers of similarly meaningful distance from the potential trial sentence (Study 3). The results also provide insight into the plea rates that might be expected under different combinations of the independent variables (Studies 2 and 3). Conclusions: These results support a new conceptual model of plea decision-making that may be better suited to explaining case-level differences in plea outcomes than the SOT model and suggest that future research extending this model to a wider range of contexts would be fruitful. Public Significance Statement In this research, we proposed and tested a psychologically informed model of guilty plea decision-making in factually guilty (mock) defendants. In three studies, we found support for the model, which suggests that defendants make decisions on the basis of broad categorical representations of perceived probability of conviction and magnitude of the differences between plea a