Brain scans of convicted Pittsburgh synagogue shooter Robert Bowers show abnormalities that could have affected his behavior and functions during the 2018 attack on Jewish worshipers, a defense expert witness testified Monday.
Erin Bigler, a clinical neuropsychologist and retired Brigham Young University professor of psychology and neuroscience, reviewed Bowers’ brain scans and psychological data collected by two other experts. Though Bigler noted that neither tests nor scans can definitively diagnose schizophrenia, he said Bowers’ brain showed asymmetries and dysfunctions often associated with the disorder.
Bowers was found guilty last month of killing 11 Jewish worshipers and wounding six people in 2018 at the Tree of Life synagogue in Squirrel Hill. Defense lawyers argue that Bowers was severely mentally ill at the time of the attack and therefore couldn’t form the kind of intent to kill required to impose a death-penalty sentence, which prosecutors are seeking.
Bigler told the jury that by the time he got involved in the case, defense lawyers were acting on the “working hypothesis” that Bowers has schizophrenia. Bigler said he examined Bowers’ brain scans and psychological data in the light of his understanding that Bowers already had received a clinical diagnosis, though he said he did not know who made the diagnosis.
A doctor hired by the defense and a doctor hired by the prosecution both administered neuropsychological tests designed to gauge Bower’s IQ, memory, executive functioning and perception, among other things. These included internal and external validity tests, all of which indicated that Bowers’ answers were valid, Bigler testified.
According to Bigler, Bowers scored in the 91st percentile on the full-scale IQ test, indicating high overall cognitive ability. Full-scale IQ includes the averages of a number of subscales, including processing speed, where Bowers scored poorly.
Bowers scored in the 18th percentile for processing speed, which “tells us that elements of processing speed in Bowers’ brain [aren’t] working quite the way that it should,” Bigler said. Typically, processing-speed scores should be in a “relatively similar ballpark” to full-scale IQ scores. Bowers also had difficulties with some memory tests, Bigler said.
Diminished processing speed and poor memory can be associated with schizophrenia, Bigler told the jury. He noted that IQ is often an incomplete measure; it doesn’t account for emotional abilities, social intelligence or decision-making, and it capitalizes on well-learned skills and academic abilities that are often cemented early in life. A person can have both a high IQ and mental health issues that negatively impact their life, he explained.
“The brain is an extremely complex organ, and its relationship with behavior is equally complex,” Bigler said.
Bowers scored poorly on some executive-functioning tests, while other test results showed no such impairments, Bigler said. He also showed some deficits related to social cognition, including “severe impairment” in matching emotion-laden speech to a person’s emotional state.
Bigler said that matches up with analysis provided by other defense witnesses, who found deficits in the amygdala and temporal lobes of Bowers’ brain, as well as high levels of white matter hyperintensities. People in their 40s, as Bowers was at the time of the test, typically have about four white matter hyperintensities, Bigler said. Bowers had 28 — mostly located in the frontal lobe, which can be associated with cognitive decline, he said. It’s unclear when the white matter hyperintensities began to develop. Bowers was also a smoker, which can contribute to the development of white matter hyperintensities, Bigler said.
“My conclusion would be that there are executive-function deficits. They’re not consistently observed,” Bigler said. “In the real world, this would indicate variable ability in carrying out executive-control tasks.”
While schizophrenia is believed to be a result of connectivity and network-dysfunction issues in the brain, Bigler stressed that scientists don’t fully understand the disorder or what causes it. The images and tests also can’t be used to definitively diagnose schizophrenia; they’re just one tool clinicians use to come to a diagnosis, he said.
During cross-examination, U.S. Attorney Eric Olshan pressed Bigler on the schizophrenia diagnosis. Olshan said that if Bigler had been told Bowers was previously diagnosed with schizophrenia, it’s possible Bigler went looking for facts that supported that existing diagnosis while ignoring symptoms that indicated Bowers does not have schizophrenia. Bigler noted that his job wasn’t to prove or disprove the diagnosis but to evaluate the brain scans and test results. Some of those results are indicative of schizophrenia but can’t be used to prove the diagnosis, he said.
Olshan also pointed out that executive functioning and memory impairments aren’t unique to schizophrenia. He added that Bowers was able to plan the attack over a period of several months and then execute it. Bigler didn’t disagree, but he added that while Bowers did well on some executive-functioning tests, he did poorly on others. That variability can indicate brain asymmetries or dysfunction, Bigler said.
The defense plans to rest its case in this phase of the trial when it resumes on Wednesday in U.S. District Court.
Prosecutors said they plan to call two witnesses to rebut defense testimony, which could take up to two days to finish. After that, jurors will begin deliberating to determine if they believe Bowers could form the intent to kill required in order for them to impose a death-penalty sentence.
