Testing the Forensic Confirmation Bias: How Jailhouse Informants Violate Evidentiary Independence

Research has demonstrated that primary confessions corrupt perceptions of forensic evidence, such as handwriting evidence. Additionally, research on secondary confessions indicates that statements made by jailhouse informants influence juror decision making to the same degree as primary confessions. The goal of the current study was to investigate whether jailhouse informant statements bias perceptions of forensic evidence. Participants were presented with a brief case summary about a bank robbery along with confession evidence from a jailhouse informant, in which both reliability and incentive presence were manipulated. Participants were then asked to examine a pair of either matching or mismatching handwriting samples before making case-relevant judgments. Results indicated that participants exposed to the reliable jailhouse informant were more likely to believe the samples were matching as well as rate them higher in similarity. These findings suggest that participants fell prey to the forensic confirmation bias.