The effects of forensic mental health reports on decisions about guilt in the Netherlands: An experimental approach

In the Netherlands, in approximately 30% of the more serious criminal cases, a pretrial forensic mental health report (FMHR) is requested to inform the court whether a mental disorder was present at the time of alleged crime, whether this disorder affected behavior and decision-making at the time of the offense and how this disorder may affect future (criminal) behavior. While informative for sentencing decisions, information about mental disorders or risk is irrelevant for the question whether the defendant committed the alleged crime. Yet based on cognitive psychological theory of evidence evaluation and integration, we hypothesized that information in an FMHR would affect the evaluation of evidence as well as the ultimate decision about guilt. Using an experimental vignette study among 200 law and criminology students with manipulation of the presence and content of an FMHR, we found a main effect of the presence of an FMHR report on decisions about guilt. The proportion of guilty verdicts increased with almost 20% when an FMHR was present compared to when this report was absent, irrespective of the type of disorder (schizophrenia or personality disorder) or level of recidivism risk (low or high) present in the report. We did not find support for our hypothesis that this effect could be explained by assimilation of other available evidence. Implications for further research and practice are discussed.