The effect of research-informed jury instructions on potential jurors' verdicts in eyewitness case vignettes

Some of the most compelling evidence against a defendant, aside from a defendant actually confessing, comes from eyewitness testimony (Yarmey, 2001). Eyewitness testimony, however, has been found to be the number one cause of wrongful convictions (Yarmey, 2001). Jurors are powerfully influenced by eyewitness testimony but are unaware and uninformed regarding the problems associated with eyewitness factors. Utilizing expert witnesses to inform jurors of eyewitness factors and developing relevant jury instructions have been identified as two ways in which jurors can make well-informed decisions in determining the guilt or innocence of a criminal suspect.;Participants (N=486) in the current study read vignettes depicting a crime and determined the likelihood that the suspect, identified as the perpetrator by an eyewitness, was guilty. Participants were randomly assigned to one of three groups. Two groups received a "facts sheet" containing evidence of the primary problems associated with eyewitness identification and testimony. Group 1 received the facts sheet prior to reading the vignette, Group 2 did not receive a facts sheet, and Group 3 received the facts sheet after reading the vignette.;It was hypothesized that participants in Group 1 would be most likely to return a not guilty verdict. In contrast to this hypothesis, results of a between-groups analysis indicated that Group 3 was significantly more likely to return a not guilty verdict than Groups 1 and 2 combined, t(483) = 4.91, p < .001. Therefore, people provided with the facts sheet after hearing the facts of the case are less likely to return a guilty verdict (based on evidence solely provided by an eyewitness) than those who receive such information before hearing the facts of the case.;As predicted, a within-groups analysis revealed that participants provided with a facts sheet on research associated with eyewitness identification and testimony were significantly less likely to return a guilty verdict than those not provided such information, t(161) = 7.23, p < .001.