His attorney, Christina Moore, has maintained that Cowell suffers from schizophrenia, and that the killing was a "rash act" fueled by psychosis. Cowell on Tuesday said he has also been treated for schizoaffective disorder, depression and bipolar disorder, and repeatedly hospitalized for mental health issues. Just three months before the attack, he was released from a maximum security psychiatric facility.
Despite that, a judge in 2019 ruled that he was mentally competent to stand trial.
Just before the fatal stabbing on July 22, 2018, Cowell rode the train from Concord to the MacArthur station in Oakland along with Nia Wilson and two of her sisters.
During direct examination, Cowell, who was removed from the courtroom last week after repeated outbursts, spoke about a radio in his head and said the three women were "pointing to other passengers while staring at me."
He added that he felt "threatened by three black females. They were together ... threatening to assault my grandmother."
Surveillance footage of the entire 25-minute ride shows no interaction between Cowell or any of the sisters. Police said Cowell pulled a hood over his head and put on sunglasses just before the attack, which occurred on the platform as the women attempted to transfer trains. Cowell later reportedly discarded his backpack and clothing in the station’s parking lot. He was taken into custody a day later at BART’s Pleasant Hill Station.
Police and prosecutors said the knife attack was unprovoked, while friends and family members of Nia Wilson have said they believe the attack was motivated by the women’s race. The Wilson sisters are black, and Cowell is white.
Cowell testified that about a week before the train ride with the Wilson sisters, he had been punched in the face by a black female.
Suggesting the possibility of a hate crime, Alameda County Deputy District Attorney Butch Ford pounced on Cowell’s mention of the sisters’ race, specifically asking the defendant if he stabbed the women because they were black.