OAKLAND (KPIX 5) — A former BART police officer testified Thursday how he unsuccessfully tried to save the life of 18-year-old Nia Wilson after she was stabbed on the platform of the MacArthur BART station in Oakland in 2018.

Defendant John Lee Cowell, 29, is charged with murder and attempted murder for allegedly stabbing the 18-year-old Wilson and her sister, 26-year-old Letifah Wilson, on the platform at the MacArthur station a year and a half ago.

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Cowell was not in court on Thursday, the day after he interrupted opening arguments with an outburst at the beginning of the trial and was removed by the judge.

Former BART police Officer Andres Rocha said he performed chest compressions and other life-saving measures on Wilson after he and another officer rushed up to the platform to try to help her shortly after 9:35 p.m. on July 22, 2018.

Rocha, who is now a deputy with the San Mateo County Sheriff’s Office, said Wilson had suffered a laceration to the left side of her head and was bleeding profusely.

Rocha said, “I attempted to keep her heart beating” but Wilson never said anything and soon died on the platform.

Wilson’s mother Alicia Grayson and other family members and friends cried as Rocha described Wilson’s last moments.

Rocha said he was already outside the MacArthur station before the stabbing because he and other officers were helping someone who had a medical problem.

Rocha said suddenly a group of people began running away from the station and screaming that there was someone with a knife.

Some of those people pointed back toward the platform to indicate that was where the problem was and Rocha later realized that one of them was Cowell, he said.

A video of Cowell running by Rocha and another officer and pointing his thumb back toward the station platform was played in court.

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Alameda County prosecutor Butch Ford alleged in his opening statement on Wednesday that Cowell tried to hide his involvement in the stabbing by quickly running away from the station, disposing of his knife at a nearby construction site and changing out of his pants and hooded sweatshirt.

Jurors also were able to examine the knife allegedly used in the crime.

On Thursday, the prosecution introduced the knife Cowell allegedly used to fatally stab Wilson. Juror were allowed to examine and hold the knife.

Cowell also is charged with a special circumstance allegation that he killed Wilson while lying in wait, a charge that would result in him being sentenced to life in prison without parole if he’s convicted. Prosecutors aren’t seeking the death penalty.

Cowell’s trial began Wednesday because Alameda County Superior Court Judge Allan Hymer, who is presiding over the case, denied a second bid by Moore last Friday to move the case away from Alameda County because she doesn’t think he can get a fair trial locally.

Hymer denied Moore’s first change of venue motion on Jan. 14, saying he would try to ensure that a fair and impartial jury is selected for Cowell’s trial by the careful questioning of small groups of potential jurors instead of bringing in large panels.

Cowell’s defense attorney Christina Moore admitted in her opening statement that Cowell stabbed Nia and Letifah Wilson, but argued that the defendant had no motive to attack the two sisters other than that he suffers from psychosis and delusion.

Moore said it was “a rash impulse” that stemmed from his schizophrenia and noted that in the weeks before the stabbing, Cowell suffered several psychotic episodes, heard voices and thought others were out to kill him.

Thursday’s testimony also included that of an AC Transit bus driver who picked Cowell up the night of the murder after the defendant had fled the scene. Video presented as evidence showed a man identified as Cowell entering the bus and saying that he needed a free ride due to an injury to his ankle.

The driver allowed Cowell on the bus and subsequently received an alert about the stabbing at the BART station after the man identified as the defendant had already exited the bus. The driver also testified that he later received a more detailed description of the suspect in the stabbing. It was that description that convinced the driver that he had given the suspect a ride.

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On Wednesday, jurors viewed graphic surveillance video of the murder during the prosecution’s opening statements which showed a man police identified as Cowell come up behind the victims and stab them in the back of the neck.