Impact of in-depth information and multimedia presentation on mock jurors’ comprehension of mitochondrial DNA evidence

In the courtroom, jurors are often faced with the task of evaluating complex scientific evidence. However, research suggests that jurors' understanding of complex scientific evidence and its reliability can be prone to error. Therefore, it is important to explore how jurors' comprehension of such evidence can be improved. The present study examined mock jurors' (N = 162) understanding of mitochondrial DNA (mtDNA) and its reliability using a 3 (evidence presentation: basic information vs. in-depth information vs. multimedia information) x 2 (evidence strength: stronger vs. weaker) factorial design. The basic information condition was kept short and served as a baseline measure of participants' knowledge on the subject. Participants read an expert witness testimony about mtDNA evidence in a robbery case and then answered 18 true/false questions to assess their understanding of the mtDNA evidence and its reliability. The strength of evidence did not have a statistically significant effect on jurors' understanding of the evidence or its reliability, and no interaction effects were observed. For the presentation of evidence, by contrast, providing in-depth information on mtDNA evidence significantly improved mock jurors' understanding of both the mtDNA evidence and its reliability. Additional illustrations presented together with the in-depth information did not further improve jurors' scores, although exploratory post-hoc analyses suggested that the multimedia information may have facilitated jurors’ understanding of some aspects of the mtDNA evidence. Theoretical and practical implications of the findings are discussed.