Are symptoms assessed differently for schizophrenia and other psychoses in legal insanity evaluations of violent crimes?

Background Forensic evaluations of legal insanity include the experts’ assessment of symptoms present at the mental state examination (MSE) and the mental state at the time of offense (MSO). Delusions and hallucinations are most important. We explored how often symptoms were recorded in written forensic reports. Design This exploratory, cross-sectional study included 500 reports of legal insanity written in 2009–2018 from cases of violent crimes in Norway. The first author read all reports and coded symptoms recorded from the experts’ assessments of the offenders. Two co-authors repeated this procedure for 50 randomly selected reports. Interrater reliability was calculated with Gwet’s AC 1 . Generalized Linear Mixed Models with Wald tests for fixed effects and Risk Ratios as effect sizes were used for the statistical analyses. Results Legal insanity was the main conclusion in 23.6% of the reports; 71.2% of these were diagnosed with schizophrenia while 22.9% had other psychotic disorders. Experts recorded few symptoms from MSO, but more from MSE, although MSO is important for insanity. We found a significant association between delusions and hallucinations recorded present in the MSO and legal insanity for defendants with other psychotic disorders, but no association for defendants with schizophrenia. The differences in symptom recordings between diagnoses were significant. Conclusion Few symptoms were recorded from the MSO. We found no association between presence of delusions or hallucinations and legal insanity for defendants with schizophrenia. This may indicate that a schizophrenia diagnosis is more important to the forensic conclusion than the symptoms recorded in the MSO.