Judicial directions and the criminal standard of proof: Improving juror comprehension

Misunderstandings by jurors of the standard of proof beyond reasonable doubt can result in miscarriages of justice. Judicial directions on the standard of proof and structured decision aids in the form of a question trail have been proposed to enhance juror understanding and application of the criminal standard of proof. Limited empirical testing exists for both. An experimental study tested the effectiveness of definitions of beyond reasonable doubt (New South Wales Criminal Courts Bench Book vs sure of guilt) and a question trail in reducing variability in the threshold to convict and jurors' cognitive load. A total of 215 jurors recruited from the Downing Centre Court in Sydney, New South Wales watched a video trial of a child sexual assault case and rendered a verdict. Exposure to instructions on the meaning of beyond reasonable doubt improved jurors' understanding of the degree of certainty required to convict. Absent this guidance, many jurors erroneously interpreted the standard to require proof beyond all doubt. Significant reductions in cognitive load were reported pre to post-verdict in all experimental conditions, including those without a question trail. In this single charge case, the question trail did not significantly improve jurors' comprehension. Substantive guidance on the meaning of beyond reasonable doubt appeared promising as a strategy to enhance juror understanding and application of the criminal standard of proof.