The role of ulterior motives, inconsistencies, and details in unreliable jailhouse informant testimony

The present study explored whether the successful detection of a jailhouse informant's ulterior motives, inconsistencies in testimony, and knowledge of privileged crime details would influence verdict decisions. Undergraduate participants (N = 381, 218 females) listened to a trial transcript in which a jailhouse informant's testimony was manipulated such that (1) the ulterior motive to provide false testimony was made salient or not, (2) an inconsistency was pointed out between the informant's testimony and a prior statement or not, and (3) an alternative explanation for how the informant learned the privileged crime details was suggested or not. Results showed both inconsistency and alternative explanation reduced conviction rates, though this was mediated by motive attributions. Participants appeared to interpret evidence differently depending on their motive attribution of the jailhouse informant. Participants who attributed the informant's behaviors to situational factors (i.e. reduced sentence) were more likely to vote not guilty and were more persuaded by the inconsistency and alternative explanation than participants who made dispositional attributions (i.e. he felt bad for the family, it's the right thing to do).