Trust but verify: The biasing effects of witness opinions and background knowledge in workplace investigations

Abstract

Introduction: A unique feature of workplace investigations is the familiarity that investigators and witnesses have with the factors involved in the adverse incident. Familiarity creates expectations that can shape investigators' and witnesses' assumptions and opinions. The current research examined the biasing effect of non-factual witness claims on investigators' judgments. These claims, which we call 'uncheckable', included opinions about factors involved in the event and the future. We also examined how participants' a priori knowledge of an employee's history influenced their judgments.Method: This experiment used a 2 (background information: control or unsafe) x 2 (uncheckable content: neutral or unsafe) between-subjects design. Participants were provided with background information about a worker (control or unsafe history) and a witness statement about a workplace event that contained uncheckable claims (neutral or worker as unsafe). We tested how our manipulations biased participants' judgments of (i) the cause of the event, (ii) the witness's confidence and credibility, and (iii) the diagnosticity of the witness's account. We also tested if biasing background information affected how factual participants found the witness’s statement.Results: Biasing uncheckable information (i.e., opinions) affected participants' judgments of event cause (ηp2 = .033) and increased their ratings of witness confidence (ηp2 = .074). Biasing background information about a worker affected participants' judgments of the cause of the event (ηp2 = .088), the diagnostic value of the witness statement (ηp2 = .054), and the number of factual claims in the witness statement, resulting in more uncheckable claims being misclassified as potential facts (ηp2 = .18). Conclusion: This experiment demonstrated the significant effect that non-factual witness statements and irrelevant background information can have on the interpretation of evidence and judgments about the cause of events.Practical Application: Understanding how contextual information can bias investigative judgment helps workplace investigators manage its influence in their judgment practices.