The murder shocked China's largest city just a month before the Beijing Olympics, and O'Brien's family and friends were stunned that it happened just as the model, unhappy with her work in Shanghai, was about to come home early.
During his trial Monday, 18-year-old migrant worker Chen Jun said he went into O'Brien's apartment because the door was open. He said she caught him taking a laptop from the living room and then ran from the apartment when he threatened her with a knife.
Chen told the court he caught O'Brien in the stairwell and stabbed her repeatedly, Chen's lawyer, Zheng Qiu, confirmed in a phone interview Tuesday.
Chen told the court O'Brien was still alive. "I decided not to help her this time," the Shanghai Daily newspaper reported him as saying. "I called the police, and they must have been here. I thought there's no need to call again."
But O'Brien's body was not found until hours after the late-night stabbing, when a janitor discovered her around 6 a.m.
Zheng, whose request for a psychological assessment of Chen was rejected by the court, said he had no comment on the case.
The telephone in the news office of the Shanghai No. 1 Intermediate People's Court rang unanswered Tuesday.
Chen was arrested four days after the stabbing in his nearby home province of Anhui. Shanghai police said they had tracked him after seeing him in footage from surveillance cameras near O'Brien's apartment building.
One of millions of migrant workers in Shanghai, Chen later told a popular Shanghai crime news show that he had lost his job at a teahouse near O'Brien's apartment in June and needed money to get home.
When he was arrested, police said they found money, jewelry, mobile phones and a digital camera from the apartment O'Brien shared with another Canadian model.