Experts' decision-making processes in Swedish forensic psychiatric investigations: A case vignette study

It has previously been demonstrated that decisions made by forensic experts can suffer from issues with both bias and poor reliability. The outcome of Swedish forensic psychiatric investigations can have a major impact on the courts' choice of sanction for a mentally disordered offender. These investigations are performed by multi-professional teams of experts, where each expert is obliged to state their opinion on whether the client has a severe mental disorder (SMD) or not. In the present study, a case vignette design was used to simulate the decision-making process of forensic psychiatric investigations. Of the 73 Swedish experts working with forensic psychiatric investigations, a total of 27 (37%) participated in the study. The results showed that the Swedish experts formulated multiple diagnostic hypotheses about cases throughout the process and revised these hypotheses when presented with new information. There was substantial variation between the experts in which hypotheses were seen as most relevant. While the experts grew more certain of their opinions on SMD during the simulated investigation, there was considerable variation in their opinions both throughout and at the end of the process. Although low statistical power and the sample not being randomized limit generalizations, the results indicate no idiosyncratic patterns in the decision-making processes of Swedish experts or signs of confirmation bias. If used properly, the variation in both process and outcome could be used to safeguard and possibly increase the reliability and validity of the final decision of Swedish forensic psychiatric investigations.