Testimony on the brain activity of a convicted murderer may have saved him from the death penalty.
Earlier this month, a jury in Miami rejected the death penalty and chose life in prison for Grady Nelson, who in 2005 stabbed his wife 61 times, killing her, and stabbed and raped her 11-year-old, mentally handicapped daughter. A report in The Miami Herald last weekend suggests that measurements of Nelson's brain activity may have influenced some members of the jury, who viewed the results as evidence of a brain injury that would partially explain his behavior. But some scientists are critical of the way this technology was used in the case. During the sentencing phase of the trial, the court heard testimony from Robert Thatcher, a neuroscientist and president of by Applied Neuroscience Inc. of St. Petersburg, Florida. Thatcher's company examined Nelson using a method called quantitative electroencephalography (QEEG). As in standard EEG, technicians place electrodes on the skull to record electrical activity in the brain. In QEEG, a computer program analyzes these recordings to locate regions of abnormal activity. In Nelson's case, there was an obvious abnormality in the left frontal lobe, Thatcher says.
Thatcher also testified that Nelson exhibited "sharp waves" originating from this region. These large spikes in the EEG trace are typically seen in people with epilepsy. Grady is not epileptic, but he does have a history of at least three traumatic brain injuries, Thatcher said yesterday in an interview.
In court, Thatcher testified that the head injuries Nelson suffered could cause this type of EEG abnormality. He also told the court that the frontal lobes are important for controlling behavior. "When the frontal lobes are damaged, people have difficulty suppressing actions ... and don't understand the consequences of their actions," Thatcher told ScienceInsider.
The QEEG data Thatcher presented were riddled with artifacts, and his analysis was undermined by serious statistical flaws, says Charles Epstein, a neurologist at Emory University in Atlanta, who testified for the prosecution. Epstein adds that the sharp waves Thatcher reported looked more like blips caused by the contraction of muscles in the head. "I treat people with head trauma all the time," he says. "I never see this in people with head trauma."
But at least some members of the jury may have been swayed by Thatcher's testimony. Six jurors voted for the death penalty. But two of those who voted against it told The Miami Herald that the QEEG evidence was influential:
Delores Cannon, a hospital secretary, said she leaned toward death until the technology was presented. "But then when it came in, the facts about the QEEG, some of us changed our mind," she said.
John Howard, an airport fleet services worker, said he, too, was ready to recommend death. "It turned my decision all the way around," Howard said the QEEG [sic]. "The technology really swayed me . . . After seing the brain scans, I was convinced this guy had some sort of brain problem."
Nelson's lawyer certainly thinks so. "This may be the first time in any United States criminal courtroom where QEEG analysis has been ruled admissible and respected for its ability to provide vital information on brain injury and impairment," defense attorney Terence Lenamon said in a press release that appears to have been issued on Nelson's behalf.
That may be a stretch. In an affidavit submitted to the court, Thatcher provided a "partial list" of 18 previous cases in which QEEG was used to establish that someone had suffered traumatic brain injury. (There are also cases in which judges have ruled that QEEG evidence is not admissible.)
In Nelson's case, however, QEEG was used to explain his behavior. That kind of application is a lot more problematic than using it to establish an injury, says Andrew Leuchter, a neurologist at the University of California, Los Angeles, who was not involved with the case.
Leuchter uses QEEG for research and says it has several valid clinical uses—such as distinguishing Alzheimer's disease from other types of dementia. "You can certainly say with a high degree of confidence from this kind of test that someone's brain is not functioning properly, and you can sometimes say what caused it," Leuchter says. "The one thing you can't do is link someone's actions to their brain function abnormality. That is well beyond anything we're capable of doing at the present time."