A jury found Cowell guilty Tuesday afternoon of murder, lying in wait, and attempted murder of Wilson's sister.
Cowell pleaded not guilty by reason of insanity.
The next phase of the trial start Wednesday.
- Heartbreaking testimony from Nia Wilson's sister in deadly BART stabbing trial
- Man accused of killing BART rider Nia Wilson thrown out of court during trial opening statements
- Judge rules Oakland BART stabbing suspect competent to stand trial
- 'He was wiping off his knife': BART stabbing victim recalls horrific attack that killed sister
- The judge threw the defendant John Lee Cowell out of court after he had more than one outburst.