Reasonable medical certainty, diagnostic thresholds, and definitions of mental illness in the legal context.

The treating psychiatrist can change his initial clinical impression as a result of his ongoing relationship with the patient and his evaluation of response to treatment. Such monitoring is difficult. if not impossible, in the usual practice of forensic psychiatry. Also, the legal consequences of judicial decisions based on psychiatric opinion may be quite serious. If the psychiatric opinion is to be influential in determining the final decision, it should be offered with as high a level of confidence as possible.