The link between suspect verbosity during investigative interviews and observer-rapport

Purpose: Rapport enhances both the quantity and quality of information in investigative interviews and is recommended by multiple frameworks and training manuals. As interviewers are trained to associate rapport with more detailed responses, they are likely to assess rapport based on the amount of information provided. However, this evaluation can be skewed by the suspect’s verbosity—more elaborate accounts by the suspect may be mistaken for interview success, even when no useful information is shared. With this study, we tested whether suspect verbosity influenced observer-rapport, and judgement of perceived suspect guilt. Methods: Participants (N = 184) listened to one of three audio recordings of a mock police interview, within a between-groups design (Suspect verbosity: Low vs. Medium vs. High), and afterwards were asked to rate rapport between the suspect and the interviewer, and suspect guilt.Results: Our results show that rapport ratings statistically significantly differ between the Low and High verbosity-conditions. Participant’s also perceived suspects as being less likely to be guilty if they spoke more words, even when this speech does not provide investigation relevant information. Conclusion: If individuals base rapport and guilt judgements on verbosity rather than an objective assessment of the evidence, it may lead to sub-optimal investigative outcomes. Therefore, it is important to further investigate how interviewer training may impact our findings.