Information integration in juror decision making

Research applying information integration theory to jury decision making has long assumed that people average informational scale values when making legal judgments. Although often consistent with research results, this hypothesis has never been tested in a legal context against a more general additive rule. The present paper describes two studies conducted as a critical test between these two models. Incriminating evidence and eyewitness confidence were varied in a full-factorial, within-subjects design involving a total of 131 subjects acting as mock jurors. Subject responses included eyewitness accuracy and defendant-guilt probability estimates, as well as final verdict decisions. Results strongly support an averaging model of legal decision making. Additional results concerning the influence of initial attitudes and the interrelationships between the variables considered are reported and their implications are discussed.