Behavioral psychologists have been studying the informant phenomenon, especially the thorny question of why jurors believe unreliable informants even when they know that the informants have strong incentives to fabricate evidence. Some of those studies can be found here in the Resources & Scholarship section.
A group of researchers recently published this study finding that information from an informant can affect other witnesses in a case. Specifically, the study found that eyewitnesses who identified suspects in a line-up actually changed their identifications after learning that a jailhouse informant had implicated a different suspect. Here is the abstract:
“Prior research has shown that primary confession evidence can alter eyewitnesses’ identifications and self-reported confidence. The present study investigated whether secondary confession evidence from a jailhouse informant could have the same effect. Participants (N = 368) watched a video of an armed robbery and made an identification decision from a photo lineup. Except for those in the no-feedback conditions, all participants then read that certain lineup members either confessed to the crime, denied involvement, or were implicated by a jailhouse informant. Jailhouse informant testimony implicating the identified lineup member led participants to have significantly higher confidence in their identification. In contrast, jailhouse informant testimony that implicated a lineup member other than the identified led participants to have significantly lower confidence in their initial identification, and 80% of these witnesses changed their identification. These results indicate that jailhouse informant testimony can influence eyewitnesses’ confidence and their identification decisions.”
Preston M. Mote & Jeffrey S. Neuschatz & Brian H. Bornstein & Stacy A. Wetmore & Kylie N. Key, Secondary Confessions as Post-identification Feedback: How Jailhouse Informant Testimony Can Alter Eyewitnesses’ Identification Decisions, Journal of Police and Criminal Psychology (2018).