Court cases across America often feature expert testimony that offers conflicting conclusions. When this happens in cases involving psychiatric expertise, does it mean that one side or the other is necessarily being less than honest?
A new study from the University of Cincinnati College of Law says the answer is no, and, for the first time, offers up mathematical modeling methods to back up that conclusion.
The study - led by Douglas Mossman, MD, director of the UC College of Law's Glenn M. Weaver Institute of Law and Psychiatry and the forensic psychiatry fellowship at the UC College of Medicine - showed that a group of psychiatrists who evaluated mental competence from case files of 156 criminal defendants performed at a strikingly high level of accuracy.
In an average of 29 out of every 30 cases, the psychiatrists could distinguish competent defendants from incompetent defendants. That's a level of performance that exceeds standard diagnostic performance in other areas of medicine, such as spotting breast cancer in mammograms or using advanced imaging methods to detect Alzheimer's disease.
It also points out one of the basic truths of the justice system, even when dealing with a topic as definitive as expert testimony: ultimate decisions still come down to judgment calls.
"These results help us see how courtroom experts can be quite accurate in distinguishing competence from incompetence, but still reach different conclusions," says Mossman of the study, which was published online in "Law and Human Behavior," the journal of the American Psychology-Law Society. "It's a matter of where experts draw the line on the issue of competence."
Continues Mossman: "Experts may disagree with each other even though they are very good at making all the right distinctions. You're apt to get disagreement when you ask experts for a 'yes' or 'no' answer, as the courts do, on issues that can have gray areas, like competence to stand trial."
Many people assume that when experts disagree, it's because they are merely "hired guns" who testify to whatever opinion they are paid to advance. The methods used in the new study dispute that assumption, and may also provide clear evidence supporting the abilities and skills of mental health experts.
"When opposing experts disagree, courtroom cross-examination often becomes an intensive effort to question the integrity of psychiatric diagnoses and to discredit all mental health expertise," says Mossman, who worked with colleagues from Wright State University's Boonshoft School of Medicine and the University of Wisconsin School of Medicine and Public Health on the study.
The problem is there is no independent, infallible "gold standard" to establish conclusions in forensic psychiatry, as there is in most other areas of medicine.