KRON4’s Amy Larson is in court daily to bring you updates on the trial of Nia Wilson‘s killer. Find all her stories here.

OAKLAND, Calif. (KRON) — John Lee Cowell is testified Tuesday about his state of mind when he killed Nia Wilson on a BART platform in Oakland.

He testified that he believed 18-year-old Wilson and her two sisters were “aliens” and “gang members” who kidnapped his grandmother and were going to hurt her.

Cowell, 29, of Concord, said he was trying to save his grandmother by stabbing “the black females.”

“There were three black females working together. They were threatening to assault my grandmother,” Cowell testified. “They were standing over me and they would not walk away from me. They were staring me down. It’s not illegal to said, save, or rescue a family member. I stabbed the females because they would not give my grandmother back.”

BART surveillance video recorded the three Wilson sisters riding on the same train as Cowell for 26 minutes on July 22, 2018. They never interacted with each other. While Cowell was on the train, he took a knife out of his backpack and hid it under his clothing, prosecutors said. When the train reached MacArthur station, video showed Cowell following closely behind the sisters before he lunged with the knife at Wilson, slashing her throat.

Cowell testified that during the summer of 2018 he was hearing voices, but he couldn’t remember what the voices were telling him. Medical records show he heard a voice telling him someone wanted to kill him.

He also made some bizarre statements about aliens planting technology in his ear and aliens putting “fake skin” on people.

“Putting someone else’s skin on. Why are black and white skin different?” Cowell remarked.

Cowell has pleaded not guilty by reason of insanity. He was released from a mental hospital not long before the homicide.

Since his 18th birthday, Cowell has been diagnosed with schizophrenia, anti-social personality disorder, bipolar disorder, and depression. He used heroin and methamphetamine daily, and he was aware that methamphetamine made him hear voices, Alameda County prosecutor Butch Ford said.

Ford showed the courtroom a surveillance image of Cowell stabbing Wilson.

“Do you remember stabbing them?” Ford asked Cowell during cross-examination.

“Yes.” Cowell replied.

“What were you doing?” Ford asked.

“Using a knife against Nia Wilson the kidnapper,” Cowell replied.

Cowell testified that it was his “prerogative” to stop the “threat” that the Wilson sisters posed by stabbing Wilson and her older sister, Letifah Wilson.

As Ford pressed Cowell with more questions about the attack, Cowell became agitated and verbally sparred with the prosecutor.

“I don’t appreciate you talking to me like that. You’re beefing with me right now. Two wrongs don’t make a right,” Cowell told Ford.

The judge ordered the court to take a recess and everyone was escorted out of the gallery.

When court went back into session Tuesday afternoon, Cowell continued to take issue with Ford.

“You were rude to me. I can’t help you out. I’m not going to do anything for you now,” Cowell said.

Ford said Cowell was “putting on a show” to convince the jury that he was insane. Cowell testified that he is not currently taking any medications, and Ford said that’s because Cowell is hoping that the jury find him not guilty by reason of insanity.

Cowell has been locked in an Alameda County jail in Dublin since his arrest. Ford said Cowell told the jail’s medical staff members that he wants to be sent back to Atascadero state mental hospital so he can eventually be released.

“You’re not taking medications because you want to appear crazy, right? Are you trying to look or appear crazy?” Ford asked Cowell.

“No,” Cowell said.

Cowell’s defense attorney came right out the gate last week during opening statements declaring that the man on trial for murder did in fact kill a young woman who he had never met.

On Monday, Wilson’s sisters took the stand to describe the day they were attacked. For 26 minutes, Wilson and Cowell rode a nearly-empty BART train a few feet away from each other. The jury viewed a courtroom projection screen Monday showing BART surveillance video of the teen living the last minutes of her life.

Wilson didn’t notice the stranger sitting silently nearby. Everyone in the courtroom, including Wilson’s friends and family, knew that when the BART train reached the MacArthur station in Oakland, she was going to die.

Alicia Greyson said, as she viewed the haunting video, she thought, “That’s my baby. Her last moments on this Earth. It’s heartbreaking. I would never image that my daughter’s last moments would actually be filmed, all the way to the demise of her.”

Cowell was thrown out of court by the judge on Day 1 of the trial for making verbal outbursts. And on Days 2 and 3, he refused to enter the courtroom.

His defense attorney, Christina Moore, said Cowell impulsively killed Wilson while experiencing delusions from schizophrenia. Ford disagreed, telling the jury that Cowell plotted the senseless attack because he is “evil.”

The prosecution rested its case Monday afternoon. As his last two witnesses, Ford called Wilson’s sisters, Letifah and Tashiya, to the witness stand. They sobbed as they recounted taking BART home with Nia the night they were followed and attacked.

“Did Nia like taking BART?” Ford asked Tashiya.

“Not at all. She thought it was nasty with germs and bacteria,” Tashiya said.

As the three sisters tried to transfer from one train to another, Tashiya stepped onto the train first. Nia Wilson and Letifah paused to let a woman pulling a baby stroller exit the train. At the exact moment that they paused, Cowell lunged and stabbed Nia Wilson and Letifah.

Letifah said she still feels pain in her neck today, but during the attack, she didn’t feel pain. Letifah was only focused on her younger sister, who was screaming and bleeding on the train platform. The woman with the stroller handed her baby blanket to put pressure around Nia Wilson’s neck.

“There was too much blood. She was bleeding too bad. That was my little sister. I’m always supposed to protect my little sister,” Letifah said as she sobbed on the witness stand. The court paused for a recess when Letifah began hyperventilating and became physically ill.

When paramedics and police arrived and began CPR on Nia Wilson, they took Letifah away to a hospital.

The morning after the homicide, “nobody wanted to tell me,” Letifah said. But finally, her father told her. Her little sister had died.

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