Forensic mental health expert testimony and judicial decision-making: A systematic literature review

Forensic mental health expertise (FMHE) is an important source of information for decision-makers in the criminal justice system. This expertise can be used in various decisions in a criminal trial, such as criminal responsibility and sentencing decisions. Despite an increasing body of empirical literature concerning FMHE, it remains largely unknown how and to what extent this expertise affects judicial decisions. The aim of this review was therefore to provide insight in the relationship between FMHE and different judicial decisions by synthesizing published, quantitative empirical studies. Based on a systematic literature search using multiple online databases and selection criteria, a total of 27 studies are included in this review. The majority of studies were experiments conducted in the US among mock jurors. Most studies focused on criminal responsibility or sentencing decisions. Studies concerning criminal responsibility found consistent results in which psychotic defendants of serious, violent crimes were considered not guilty by reason of insanity more often than defendants with psychopathic disorders. Results for length and type of sanctions were less consistent and were often affected by perceived behavioral control, recidivism risk and treatability. Studies on possible prejudicial effects of FMHE are almost non-existent. Evaluation of findings, limitations and implications for future research and practice are discussed.