Diverging from the shadows: explaining individual deviation from plea bargaining in the “shadow of the trial”

Objectives The “shadow of the trial” (SOT) theory posits that plea decisions result from mathematical predictions of probability of conviction (POC) at trial and potential trial sentence (TS). Tests of the SOT model often find support in the aggregate, but not at the individual level. This study examines the factors that account for adherence to, or deviation from, the SOT model, such as mathematical competence, a factor not previously examined in tests of the SOT model. Methods Participants were randomly assigned to one of nine conditions corresponding to manipulations of probability of conviction (10%, 50%, 90%) and potential trial sentence (5, 15, 25 months). After reading a case description, participants were asked whether they would accept a plea offer and how much time in jail they would be willing to spend; a subset of participants was offered a counter plea offer. Participants then answered questions assessing numeracy and about their legal opinions and personal characteristics. Results Results showed that probability of conviction, but not trial sentence, influenced shadow model adherence. Participants assigned to 50% and 90% POC conditions were significantly less likely to deviate from the SOT model than participants assigned to 10% conditions. This effect did not interact with TS. Additionally, the odds of fitting the SOT model increased significantly as participants’ numeracy scores increased. Conclusions Our results raise questions about the validity of the SOT model at low POCs and challenge its assumption that defendants are capable of conducting the mathematical calculations required to fit the model.