Strength of Evidence,Extraevidentiary Influence,and the Liberation Hypothesis: Data from the Field

To examine relationships between strength of evidence (SOE) and extraevidentiary variables in the context of Kalven and Zeisel’s (The American Jury, 1966) liberation hypothesis, post-trial questionnaire data were collected from judges, attorneys, and jurors associated with 179 criminal jury trials. SOE ratings were strongly correlated with jury verdicts on the three most serious charges against the defendant, and several extraevidentiary variables (i.e., pretrial publicity, trial complexity, charge severity, and foreperson demographics) were moderately correlated with verdicts. Extraevidentiary-verdict relationships remained significant when SOE was controlled, although extraevidentiary variables yielded only modest improvement in classification accuracy beyond SOE. In partial support of the liberation hypothesis, several case-related extraevidentiary variables were significantly related to jury verdicts only when the prosecution’s evidence was rated as moderately strong.