A re-examination of the acquittal biasing effect of offence seriousness

The justice system should operate free of bias, and jurors’ judgements of a defendant's guilt should be based on evidential factors alone. However, research suggests that this is not always the case. The aim of this study is to investigate the biasing effect of offence seriousness – a case-related, extralegal factor – on juror decision-making. An experiment was conducted to examine the effect of this extralegal factor on 118 members of the jury-eligible public’s interpretations of ‘beyond reasonable doubt’ (BRD), probability of commission, verdict and confidence in verdict. It was found that defendants charged with more serious offences were judged to be less likely to have committed the crime. However, offence seriousness was not found to have a significant effect on interpretations of BRD and verdict. The present findings suggest a need to instruct jurors on the application of legal (probative) factors alone.