Despite that possibility, Nelson said the numbers are very small for cases in which legitimate differences of opinion may arise, because prosecutors will have already winnowed out those cases of moderate or severe mental retardation at the competency phase. "I've done 150 capital murder cases and have put forward mental retardation as a mitigating factor in only three of them," Nelson said. "And that's not a surprise...Mental retardation is [present in] only about 1% of the general population, so even if it's 3% of capital murder defendants, that's still a small percentage."
But even that small percentage is too high for Abraham L. Halpern, M.D., professor emeritus of psychiatry at New York Medical College, past president of the American Academy of Psychiatry and the Law, and past president of the International Academy of Law and Mental Health. He insists that participation in the evaluation process when it comes to death penalty cases violates ethical strictures against harming patients.
In addition to artificial battles that occur over IQ level, he also believes that assessments of adaptive function can create problems, particularly when someone has worked to make adjustments despite a low IQ. These machinations, particularly when a life is at stake, are an abuse of psychiatry, according to Halpern.
"The criteria [for evaluating who is mentally retarded] from my perspective? Psychiatrists should not be involved in examining people for competency to be executed," Halpern told PT. "The whole system is doomed to failure and it's just a matter of misusing psychiatry. The people who want to execute will simply get a psychiatrist to give an opinion that conforms with their desire."
That view may not be far off the mark, according to Richard G. Rappaport, M.D., a forensic psychiatrist and associate clinical professor of psychiatry at the University of California, San Diego, School of Medicine. Confirmatory bias, an inclination to perceive in ways that support one's point of view, pervades every aspect of criminal proceedings and affects all participants. It is a phenomenon that will not change, he said, and it will have an impact on assessments of those individuals who are in the gray zone of mental retardation.
"One of the things I experience the most as a forensic psychiatrist is the criticism that it's not a science, that it's an art, and that's why there are people testifying on both sides, there are different opinions, and there's no objective truth," Rappaport told PT. "I usually respond that there are gray areas in every science."
In an amicus curiae brief filed jointly by the APA and the American Psychological Association, the groups explained to the Supreme Court that most of the time the issue of whether someone is mentally retarded is not controversial, said Jeffrey L. Metzner, M.D., clinical professor of psychiatry at the University of Colorado Health Sciences Center in Denver and chair of the APA's Council on Psychiatry and the Law. Although he does not agree with Justice Scalia's statement that mental retardation is easily feigned, he understands what may have generated the comment.
"I can understand why the dissent might have said what he said when he looks at transcripts where you have professionals arguing about whether someone is mentally retarded or not," Metzner told PT. "But I think more often than not there is no controversy in making that diagnosis."