Beyond a reasonable doubt: ordinary people’s views of an extraordinary concept

Beyond a reasonable doubt (BRD) is the standard of proof required for conviction in criminal trials in Anglo-American legal systems. We examined how lay people (N = 220) define BRD in qualitative terms, and quantitatively measured their perceptions of existing definitions of this standard of proof as well as the grounds they believe create ‘a reasonable doubt’. The qualitative data suggests that although individuals used relevant synonyms for BRD (i.e., degree of doubt present, certainty or probability required, amount and strength of proof provided, and alternative explanations beyond the defendant being guilty), the concept is vague in individuals’ minds, has variable meanings across people, and its interpretation can increase or reduce the threshold for conviction. There was no significant difference between the sure and firmly convinced definitions of BRD (used in England and Wales, and the US Federal courts, respectively) in terms of self-reported understanding, confidence in application, and judged likelihood of wrongful conviction or wrongful acquittal. However, for each of these two definitions, greater self-reported understanding was significantly positively associated with greater confidence in applying the standard of proof, and both self-reported understanding and confidence were significantly negatively associated with judged likelihood of wrongful conviction and wrongful acquittal. Finally, a weak prosecution case and strong defence case were each rated as creating significantly greater grounds for a reasonable doubt than either victim and offender behavior or the punitive impact of a guilty verdict. The present findings have implications for jury instructions.

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