PITTSBURGH (AP) — The man who gunned down 11 people at a Pittsburgh synagogue does not have a psychiatric or neurological disorder, and he was capable of forming the intent to kill, a neurologist testified Wednesday at the killer's federal death penalty trial.

Dr. Ryan Darby, of Vanderbilt University Medical Center, was called by prosecutors to rebut defense experts who previously testified that Robert Bowers is psychotic and has brain abnormalities.

Bowers, 50, a truck driver from suburban Baldwin, was convicted last month of killing members of three congregations who had gathered at the Tree of Life synagogue on Oct. 27, 2018. He also wounded two worshippers and five police officers.

The penalty phase of Bowers’ trial began June 26 and is expected to last several weeks. Defense lawyers are trying to persuade a jury to spare his life, while federal prosecutors are seeking a death sentence.

Last week, defense experts testified that Bowers was “blatantly psychotic,” with a long history of mental illness. Bowers’ lawyers are trying to show that his ability to form the legal intent to kill was impaired by mental illness and his delusional belief that he could stop a genocide of white people by killing Jews.

But Darby asserted Wednesday that mental illness did not appear to play a role in the nation’s deadliest antisemitic attack.

The neurologist told jurors he examined Bowers for more than three hours in May, finding the defendant to be calm, cooperative and keen on talking about Jews, immigrants and his belief in a racist conspiracy theory known as the “great replacement.”

Darby, who also reviewed scans of Bowers' brain, disagreed with defense experts' assessment that Bowers has schizophrenia — a serious brain disorder whose symptoms include delusions — as well as a seizure disorder and brain abnormalities.

He said Bowers' toxic views about Jewish people were reinforced by antisemitic material he viewed online and were not the result of a delusion or psychosis.

“He saw himself as a soldier" in a war against white people, Darby testified. He said Bowers told him that if he had a chance to attack the synagogue again, he would kill more people.