The reliability of evidence about psychiatric diagnosis after serious crime: Part I. Agreement between experts.

The purpose of this study was to assess the extent of agreement on psychiatric diagnosis in written evidence provided by experts in serious criminal matters in Australia. We found good or very good inter-rater agreement on the diagnoses of acquired brain injury, schizophrenia-spectrum psychosis, substance-induced psychotic disorder, and intellectual disability. There was moderate agreement on the diagnosis of depressive and personality disorders. Agreement on anxiety disorders, in particular post-traumatic stress disorder, was poor. Agreement on the principal Axis I diagnosis was moderate, and there was a similar probability of agreement within pairs of experts engaged by the same side and those engaged by opposite sides. Concern about bias in expert psychiatric opinion in criminal cases appears to have been overstated. There was little evidence to suggest that experts' adversarial roles influenced their opinions on psychiatric diagnosis.