Evidence Evaluation in Complex Decision Making

This study investigates the role of representation of evidence in a juror's decision process. A model is presented that includes an initial stage of processing in which cognitive representations of the evidence in the form of stories are produced. This is followed by a computation of the decision by evaluating the goodness-of-fit of the evidence representation (story) to the verdict categories. Subjects, drawn from jury pools, made individual decisions on the verdicts for a filmed murder trial. Extensive interviews provided the data for analysis of their cognitive representations of the evidence in the case, the verdict categories presented in the trial judge's instructions, and the procedures they were to follow according to law to reach a verdict. We found, as hypothesized, that the trial evidence was represented in a story form. Furthermore, differences among jurors in cognitive representations of evidence were correlated with their verdicts, although other aspects of the decision process (verdict category representations, application of the standard of proof procedural instruction) were not. We conclude that adequate theories of decision making must emphasize cognitive aspects of performance, such as the representation of evidence.