Jurors’ Subjective Certainty and Standards of Proof: The Role of Emotion and Severity of Charge in Subjective Probability Judgment

Recent empirical research suggests that jurors struggle to understand and correctly apply the standard of proof. Many researchers have focused on methods to re-write jury instructions so that standards of proof are clearer and easier for jurors to understand. This dissertation suggests the fundamental cause of jurors’ confusion concerning standards of proof is that jurors may use different decision processes (intuitive decision processing or systematic decision processing) and decision indices (objective probabilistic judgment or subjective confidence) depending upon their transient emotions or the seriousness of charge. Study 1 assessed whether experiencing particular emotions (sadness or anger) could change mock jurors’ decision styles and their application of the standard of proof. Study 2 examined whether the severity of the charge against the defendant and the order of questionnaire administration could influence mock jurors’ fact processing and final verdicts. Results of study 1 showed that mock jurors induced to feel incidental sadness used rational decision processing, employed standards of proof, and made use of strength of evidence (objective probability information) as the law intended. In contrast, mock jurors induced to feel incidental anger relied on intuitive processing, and failed to make appropriate use of standards of proof and the strength of the evidence. Results of study 2 indicated that the order of questionnaire administration influenced mock jurors’ decision styles. When mock jurors assessed case arguments before reaching verdicts, they used rational decision processing and followed the order of questionnaires. In contrast, when mock jurors decided verdicts first, they relied on intuitive processing. However, contrary to expectations, the severity of charges did not influence mock jurors’ decision styles. The results of these studies suggest that jurors’ misunderstanding of the standard of proof may arise from the different types of fact-finding processes they use. Trial characteristics (i.e., severity of charge) or incidental emotion might contribute varied styles of processing that characterizes jurors’ decision-making. Implications of these results and possible future studies are discussed. Advisor: Richard L. Wiene