Research has shown that confirmation bias plays a role in legal and forensic decision-making processes and, more specifically, child interviews. However, previous studies often examine confirmation bias in child interviews using non-abuse-related events. We enrich the literature by examining interviewers’ behaviours in simulated child sexual abuse (CSA) cases.

In the present study, we used data from a series of experiments in which participants interviewed child avatars to examine how an assumption of abuse based on preliminary information influenced decision-making and interviewing style. Interview training data (N _interview = 2084) from eight studies with students, psychologists and police officers (N = 377) were included in the analyses.

We found that interviewers’ preliminary assumption of sexual abuse having taken place predicted 1) a conclusion of abuse by the interviewers after the interview; 2) higher confidence in their judgement; 3) more frequent use of not recommended question types and 4) a decreased likelihood of reaching a correct conclusion given the same number of available relevant details.

The importance of considering how preliminary assumptions of abuse affect interview behaviour and outcomes and the implications for the training of investigative interviewers were discussed.