Confirmation Bias and the Burden of Proof in Criminal Jury Trials

Lowes, Duncan (2014). Confirmation Bias and the Burden of Proof in Criminal Jury Trials Honours Thesis, School of Psychology, The University of Queensland.

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Author Lowes, Duncan
Thesis Title Confirmation Bias and the Burden of Proof in Criminal Jury Trials
School, Centre or Institute School of Psychology
Institution The University of Queensland
Publication date 2014-10-08
Thesis type Honours Thesis
Supervisor Blake McKimmie
Total pages 133
Language eng
Subjects 1701 Psychology
Abstract/Summary This research investigated whether the burden of proof instruction in criminal jury trials introduces a confirmation bias. The burden of proof instruction is one of two instructions intended to ensure the presumption of innocence and protect the defendant by placing the burden of proof of guilt entirely on the prosecution. Previous studies on jury instructions have found evidence of backfire effects with some instructions having unintended effects on jurors’ decision-making. To date most research on instructions has also focussed on comprehension rather than application of instructions. Therefore, this study investigated whether the application of the standard burden of proof instruction would have an unintended effect by placing jurors in a confirming frame of mind. Student mock jurors (N = 161) listened to a simulated trial with a between-subjects manipulation of burden of proof (standard or none) and case strength (strong or weak). Jurors gave a verdict and completed a questionnaire on their perceptions of the case. It was hypothesised that verdict, guilt likelihood, and elaboration about evidence would be less sensitive to case strength in the standard burden condition than the no burden condition. Results showed that verdict, perception of guilt likelihood, and level of elaboration were explained by evidence strength alone with no significant effects of burden of proof or differences in sensitivity to case strength. Therefore the hypothesis of a confirmation bias was not supported. This confirmed some previous findings in the literature that jurors use evidence more than instructions in decision-making. Findings are discussed in terms of the jurors’ lack of apparent bias and their limited attention to or comprehension of the burden of proof instruction.
Keyword Confirmation bias
burden of proof

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Created: Wed, 29 Apr 2015, 10:54:31 EST by Anita Whybrow on behalf of School of Psychology