Incentivized to Testify: Informant Witnesses

Abstract

This chapter explores an emerging area of psychology and law: informant witnesses. Since the introduction of plea-bargained testimony, informant witnesses have come forward with information that has led to wrongful convictions. An informant witness can be an accomplice witness, who, through their own admission, has participated in a crime and is willing to testify regarding the role of a co-conspirator, or a jailhouse informant who provides testimony about a crime based on information obtained while incarcerated. The first 250 DNA exoneration cases were examined and found that 21% involved false informant testimony. Despite its pervasiveness and contribution to wrongful convictions, the use of informants is largely unregulated. Courts traditionally have assumed that jurors appreciate the inherent unreliability of informant testimony; however, psychological research has found that informant testimony is extremely persuasive when compared to other evidence and can even effect eyewitness decisions. Existing trial mechanisms—namely jury instructions and cross-examination—are meant to sensitize jurors to view informant testimony with skepticism, but thus far, neither jury instructions nor cross-examinations have been successful. In order to understand why jurors may be unable to accurately evaluate informant testimony, we discuss how the fundamental attribution error, prosecutorial vouching, and reliance on heuristic thinking may influence these evaluations. Lastly, we address other possible legal safeguards that may prevent wrongful convictions based on informant testimony.