SAN ANTONIO -- The murder weapons that mentally ill defendants are alleged to have used vary greatly depending on the defendant's psychiatric diagnosis, Dr. Richard Frierson said at the annual meeting of the American Academy of Psychiatry and the Law.
Dr. Frierson of the department of psychiatry at the University of South Carolina, Columbia, and his colleagues performed a retrospective review of the records of 270 pretrial murder defendants who were admitted to a local psychiatric institute over a 5-year period for court-ordered evaluation. The records included a diagnostic interview, a social history, psychological tests, a neurological evaluation, MRI or CT scans, an EEG, and an assessment of the patient's competency, criminal responsibility, or capacity to conform his or her behavior to the law, depending on the reason for admission.
The researchers found that one-third of the patients had been diagnosed with mood or anxiety disorders, while an additional 30% had either borderline intelligence or were mentally retarded. About 14% of the patients had either a psychotic disorder or dementia, and the rest had a variety of other disorders--including antisocial personality disorder and borderline personality disorder--or were malingering.
When the researchers looked at the various diagnoses and the murder weapons used, they found that dementia patients used guns 81% of the time. But Dr. Frierson said this finding might be partly attributable to the fact that these patients were older and frailer and may not have had the strength to use a weapon such as a knife, which requires force.
Psychotic patients were more evenly divided, with 36% using a knife, 31% using a gun, and 32% using some other weapon. …