Secondary Confessions, Expert Testimony, and Unreliable Testimony
Two experiments examined two potential safeguards intended to protect accused persons against unreliable testimony from cooperating witnesses. Participants in both experiments read a trial transcript where secondary confession evidence was presented from either a jailhouse informant (Experiment 1 and 2) or an accomplice witness (Experiment 2). In Experiment 1, testimony history was manipulated so that participants were informed that the jailhouse informant had testified as an informant in 0, 5, or 20 previous cases. In Experiment 2, participants were exposed to an expert who testified about the unreliable nature of testimony from cooperating witnesses. The results of both experiments demonstrated that participants who were exposed to secondary confession evidence were significantly more likely to vote guilty than were participants in the no secondary confession control group. Contrary to expectations, the percentage of guilty verdicts did not vary with incentive, testimony history, or expert testimony. Explanations for these results are discussed, as are the practical challenges of using testimony from cooperating witnesses.