Comparing Fact-Based and Traditional Jury Instructions with Judge and Jury Verdict Agreement: A Trans-Tasman Field Study

Objective: Before juries deliberate, judges are tasked with instructing juries on the legal matters to be decided. It is common for jurors to experience difficulties understanding and applying jury instructions given the novel nature of the task and complexity of the law. Research indicates that instructions embedded with facts from the case may help improve jurors’ abilities to apply the law to the facts of the case. This study tested whether fact-based instructions improved the accuracy of juries’ verdicts by comparing the level of verdict agreement between judges and juries from jurisdictions that do or do not employ the fact-based approach. Hypotheses: Trials where the jury received fact-based instructions would have higher rates of judge and jury verdict agreement compared to those where the jury received standard instructions. Increased rates of verdict agreement associated with the fact-based approach would be highest amongst guilty verdicts. Methods: As part of a field trial, the rates of judge and jury verdict agreement between n = 45 cases from New Zealand (fact-based instructions) to n = 41 matched trials in Australia (traditional instructions) were compared. Analyses controlled for trial and juror characteristics, and several juror deliberation perceptions. Results: Fact-based instructions did not improve rates of judge-jury verdict agreement. However, fact-based instructions were associated with significantly higher ratings of jurors’ understanding of the judge’s instructions which in turn predicted higher rates of judge-jury verdict agreement. The results suggest that the jury’s understanding of the judge’s instructions and the extent to which the jury follows the judge’s instructions are associated with the juries accurate understanding and application of the law in real trials.