The reliability of evidence about psychiatric diagnosis after serious crime: part II. Agreement between experts and treating practitioners.

In this second part of our study, we examined the extent of agreement between treating practitioners and expert witnesses on psychiatric diagnoses in evidence presented in criminal proceedings. We found good agreement on diagnoses of acquired brain injury, schizophrenia-spectrum psychoses, depressive disorders, intellectual disability, substance abuse, and personality disorders; fair agreement on substance-induced psychotic disorder; and poor agreement on the presence of anxiety disorders. A proportion of defendants with diagnosis by experts of substance-induced psychotic disorder also had a diagnosis of schizophrenia-spectrum psychosis by treating practitioners. Treating practitioners and experts engaged by the prosecution rarely made the diagnosis of post-traumatic stress disorder. Overall, there was moderate agreement between experts and treating practitioners on the principal Axis I disorder, and the evidence for psychiatric diagnoses presented by treating practitioners in criminal cases was found to be generally reliable.