The case of Teresa Lewis is one of dozens of skirmishes in U.S. death penalty states spawned by the Supreme Court's 2002 decision outlawing capital punishment for the mentally retarded. In the years since the Atkins ruling, an estimated 7 percent of condemned prisoners have filed claims on the basis of mental retardation, with about 40 percent succeeding in getting their death sentences overturned.
Central to these battles are opposing experts in forensic psychology. Their role illustrates the fundamental problem with science in court. The law asks a simple, black-and-white question: Is this person's IQ above or below the magic threshold for mental retardation (typically, an IQ score of 70)? Lewis scored 73 and 70 on IQ tests administered since her trial. Such minimal score differences are within the range of random fluctuations and are practically meaningless in a clinical context. But in the legal context, they can be the difference between life and death.
Psychology, in contrast to the law, sees nuances and shades of gray. An IQ score is only one data point, and must be combined with other relevant information to give a meaningful picture of a person's functional capacities. Here, a central issue is Lewis's personality style.
Lewis was sentenced to die under the theory that she masterminded the killing of her husband and stepson for a $350,000 life insurance policy. Although both triggermen received life sentences, Judge Charles Strauss gave Lewis the death penalty, reasoning that she was "clearly the head of this serpent," according to an account in yesterday's Huffington Post.
But new evidence suggests Lewis may have been manipulated into the crime. In a letter written before he killed himself in prison, gunman Matthew Shallenberger said the crime was entirely his idea, and he deliberately manipulated Lewis because he needed money and she "was an easy target."
Three forensic psychology experts have diagnosed Lewis with a dependent personality disorder. She is reportedly so dependent on others that she cannot make even simple decisions such as what to buy at the grocery store. Lewis's chaplain at Fluvanna Correctional Center for Women similarly described Lewis in a Newsweek essay appealing for clemency as "slow and overly eager to please -- an easy mark, in other words, for a con."
The state Supreme Court, a U.S. District Court, and, most recently, a U.S. Court of Appeals, have all upheld the death sentence. The execution, which will be Virginia's first killing of a woman in almost a century, is set for Sept. 23. She gets to choose between the electric chair or lethal injection.
Perhaps she should choose the latter; Kentucky, Oklahoma, and some other states may have to delay executions due to a shortage of one of the drugs in their lethal cocktails.
Related blog post (with additional links to resources):
- Atkins claims: Did Texas psychologist skew data for death? (Jan. 10, 2010)