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  1. The law expects jurors to weigh the facts and evidence of a case to inform the decision with which they are charged. However, evidence in legal cases is becoming increasingly complicated, and studies have raised questions about laypeople’s abilities to understand and use complex evidence to inform decisions. Compared to other studies that have looked at general evidence comprehension and expert credibility (e.g. Schweitzer & Saks, 2012), this experimental study investigated whether jurors can appropriately weigh strong vs. weak DNA evidence without special assistance. That is, without help to understand when DNA evidence is relatively weak, are jurors sensitive to the strength of weak DNA evidence as compared to strong DNA evidence? Responses from jury-eligible participants (N=346) were collected from Amazon Mechanical Turk (MTurk). Participants were presented with a summary of a robbery case before being asked a short questionnaire related to verdict preference and evidence comprehension. (Data is from the pilot of experiment 2 for the grant project). We hypothesized participants would not be able to distinguish high- from low-quality DNA evidence. We analyzed the data using Bayes Factors, which allows for directly testing the null hypothesis (Zyphur & Oswald, 2013). A Bayes Factor of 4-8 (depending on the priors used) was found supporting the null for participants’ rating of low vs. high quality scientific evidence. A Bayes Factor of 4 means that the null is four times as probable as an alternative hypothesis. Participants tended to rate the DNA evidence as “high quality” no matter the condition they were in. The Bayes Factor of 4-8 in this case gives good reason to believe that jury members are unable to discern what constitutes low quality DNA evidence without assistance. If jurors are unable to distinguish between different qualities of evidence, or if they are unaware that they may have to, they could give greater weight to low quality scientific evidence than is warranted. The current study supports the hypothesis that jurors have trouble distinguishing between complicated high vs. low quality evidence without help. Further attempts will be made to discover ways of presenting DNA evidence that could better calibrate jurors in their decisions. These future directions involve larger sample sizes in which jury-eligible participants will complete the study in person. Instead of reading about the evidence, they will watch a filmed mock jury trial. This plan also involves jury deliberation which will provide additional knowledge about how jurors come to conclusions as a group about different qualities of evidence. Acknowledging the potential issues in jury trials and working to solve these problems is a vital step in improving our justice system. 
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