OAKLAND (CBS SF) — The lawyer for the man accused of fatally stabbing Oakland teenager Nia Wilson in a random attack at the MacArthur BART station told a judge Thursday her client suffers from paranoia and is not fit to stand trial for murder.

The declaration came at a plea hearing for 28-year-old John Lee Cowell, who has been charged with murder and attempted murder for the stabbing death of Wilson and the stabbing of Letifah Wilson, her 26-year-old sister, at the MacArthur station at 9:36 p.m. on July 22.

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Prosecutors have added a special circumstance allegation that Cowell killed Wilson while lying in wait, an allegation that could result in the death penalty or life in prison without parole if he’s convicted.

Defense lawyer Christina Moore told the judge Cowell suffers from extreme delusion and paranoia. He was released from the Atascadero State Hospital, an all-male, maximum-security facility that houses mentally ill convicts who have been committed to psychiatric facilities, only 75 days before Wilson was killed.

“We’re seeing a very extreme level of mental illness, and it’s clear he’s not able to rationally assist me in his defense at this time,” Moore said outside the courtroom.

No plea was entered Thursday and the judge ordered Cowell to return to court on Dec. 27th to consider the incompetency claim.

Wilson’s friends and family members packed the courtroom. Her mother, Alicia Grayson, spoke outside.

“He ain’t crazy. He went crazy that night,” said Grayson.

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Grayson said Cowell looked competent in court Thursday morning and at one point spoke to his lawyer out of the camera’s view.

“He knows how to behave himself. If he was crazy, he wouldn’t know how to behave himself,” Grayson told KPIX 5.

The judge is now considering allowing two court-appointed psychologists to evaluate Cowell and suspending criminal proceedings. If Cowell is deemed incompetent, he could be committed to a state hospital instead of prison.

Cowell’s court appearance came less than 24 hours after an emotional graduation ceremony for Wilson’s classmates at Oakland’s Dewey Academy. Placed in Wilson’s seat were a photo, flowers and a mortar board.

The ceremony was filled with references to Wilson, including a video and speeches. Perhaps the most heartwarming moment was when her mother and father stepped on stage to accept their daughter’s diploma.

Nia Wilson’s parents smiled as they accepted their late daughter’s diploma. (CBS)

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“I’m very proud. This is an achievement that me and my daughter sat down and talked about several times. It’s so heartbreaking that she’s not here to experience this for herself,” Ansar Mohammed told KPIX 5.