This research examines the role of confirmation bias in prosecutorial decisions before, during and after the prosecution. It also evaluates whether confirmation bias is reduced by changing the decision maker between arrest and prosecution. In Experiment 1, Swedish prosecutors (N = 40) assessed 8 scenarios where they either decided themselves or were informed about a colleague's decision to arrest or not arrest a suspect. Participants then rated how trustworthy the suspect's statement was as well as the strength of new ambiguous evidence and the total evidence. They also decided whether to prosecute and what additional investigative measures to undertake. In Experiment 2 the same method was used with Law and Psychology students (N = 60). Overall, prosecutors' assessments before the prosecution indicated that they were able to act as their own devil's advocate. Also, their assessments while deciding about whether to prosecute were reasonably balanced. However, after pressing charges, they displayed a more guilt-confirming mindset, suggesting they then took on the role as crime fighters. This differed from the student sample in which higher levels of guilt confirmation was displayed in relation to arrested suspects consistently before, during and after a prosecution decision. The role of prosecutors' working experience is discussed.

This research tests whether a police officer's decision to apprehend a suspect triggers confirmation bias during an interrogation. The study also tests two strategies to reduce confirmation bias: (1) decoupling decision to apprehend from interrogation and (2) reducing cognitive load for the interrogating police officer. In Experiment 1, Swedish police officers ( = 60) were faced with 12 scenarios in which they either had to decide for themselves whether to apprehend a suspect or were informed about the corresponding decision by another police officer or a prosecutor. Participants then prepared questions for a suspect interrogation and evaluated the trustworthiness of the suspect's denial or confession. The same method was used in Experiment 2 but with law and psychology students ( = 60) as participants. In Experiment 3, psychology students ( = 60) prepared interrogation questions either by freely producing their own or by choosing questions from a preset list. Overall, apprehended suspects were interrogated in a more guilt presumptive way and rated as less trustworthy than non apprehended suspects. However, the tested debiasing techniques, primarily reducing cognitive load for the interrogating police officer, hold some potential in mitigating this bias. (PsycINFO Database Record

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Confirmation bias is a tendency to search selectively for and emphasize information that is consistent with a hypothesis or preferred conclusion. At the same time, opposing information is ignored or interpreted in ways that do not threaten the predetermined conclusion. Importantly, confirmation bias is a more or less subconscious phenomenon. Hence, legal actors and criminal practitioners who are expected to be objective, who may make genuine efforts to be objective, and who also perceive of themselves as objective, may still display a confirmation bias. This includes police officers, crime scene investigators, forensic analysts, pathologists, prosecutors, and judges, and the range of distinct decision-making tasks that these actors undertake; for example, interviews with suspects, witnesses, plaintiffs, crime scene investigations, autopsies, decisions about whether to press charges, and whether to convict. Since confirmation bias can be present at all stages of criminal investigations and proceedings, it constitutes a serious risk of error, for example resulting in wrongful convictions and wrongful acquittals. It is therefore essential to find and use bias mitigation measures, and a good starting point is the explanations of this bias provided in cognitive, emotional and motivational, social and organizational psychology. This includes measures such as changing decision-maker, contextual information management, linear sequential unmasking, and structured evaluations of the evidence.