INNOCENT OR GUILTY: What factors affect jurors’ comprehension of DNA evidence, and does comprehension effect their verdict?

Abstract

BACKGROUND AND AIMS The impact of DNA evidence on juror decision making is critical. Jurors find DNA evidence the most reliable form of forensic evidence, and cases where DNA is presented by the prosecution are more likely to lead to a conviction. However, the way DNA is presented in court is often complex and difficult for jurors to understand. This study aimed to explore how comprehension of DNA evidence effects conviction rates, as well as confidence that the right verdict was reached. We also investigated how levels of education effect both comprehension and rates of conviction. METHOD 270 participants read a summary of a crime where DNA evidence was found. Participants were then presented with expert witness testimony explaining the DNA evidence and how it was analysed. The ‘complex’ condition testimony had a Flesch readability score of 38 (University reading level). The ‘simple’ condition had a Flesch readability score of 62 (approximately year 10 reading level). Participants were then asked questions to test their comprehension of the testimony, if they found the defendant guilty or innocent, and how confident they were in the verdict. RESULTS The data showed that participants in the simple condition had higher comprehension scores than in the complex condition, and there was a higher rate of conviction in the simple condition. Data also showed that participants with a bachelor’s degree were more likely to convict than those who completed year 12.