The last image a young man in China saw on the webcam while chatting with his girlfriend in Toronto was of a man – naked from the waist down – turning off the computer moments after forcing his way into her apartment, a jury heard Monday.

York University student Qian Liu, 23, was found dead the next morning, April 15, 2011, in her off-campus basement apartment.

On the first day of the first-degree murder trial for Brian Dickson, the man accused in her death, the jury saw video and photographs of Liu's body, lying face down next to her bed, naked except for a nightgown and sweater, which were pulled up to her shoulders. Blood could be seen on the floor around her face.

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Liu's parents, who came from China for the trial – expected to last three weeks – wiped tears from their eyes as the scene of their daughter's death was displayed on courtroom screens and an interpreter relayed to them the evidence. The accused had no visible reaction.

Dickson, who lived in the same building as Liu, has pleaded not guilty to first-degree murder. His lawyer, Robert Nuttall, told the jury he is urging them to instead find Dickson guilty of manslaughter.

"This is not a who did it case," Nuttall said in brief opening remarks.

"This is a what happened case. The mechanism of Ms. Liu's death is very significant evidence in deciding whether the Crown has proven its case is murder beyond a reasonable doubt."

Pathologists could not conclusively determine Liu's cause of death, though one is of the opinion it involved neck compression, Crown attorney Christine Pirraglia said in her opening address.

Forensic scientists, however, were able to determine that Dickson could not be excluded as the source of male DNA and semen on Liu's body to a high degree of probability, Pirraglia said.

Their figures represent the probability that a randomly selected person unrelated to Dickson would share the same profile.

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That probability for male DNA found on Liu's breasts is an estimated 1 in 25 trillion, Pirraglia said. The probability for semen found on Liu's abdomen and groin area was calculated as 1 in 2.7 quintillion, she said.

The degree of probability was also quite high for male DNA found under Liu's fingernails, and Liu couldn't be excluded as the source of blood found on a T-shirt in Dickson's room, Pirraglia said.

When Dickson was interviewed by police he said he had been at a restaurant on the York University campus that night, leaving around 12:30 a.m. and going to sleep soon after, Pirraglia said. He told police he had met Liu a few times and had briefly been in her room twice. He said he had only ever touched her by shaking her hand and touching her on the shoulder, and that they had never been intimate and he did not kill her, Pirraglia said.

Liu, who was enrolled in a preparatory course at York University, was chatting with her boyfriend Xian Meng that night using both a webcam and an instant messaging service. Some time after 1 a.m. there was a knock on her door, Pirraglia said.

Meng watched Liu open the door and briefly chat with a man before he tried to hug her, Pirraglia said. She tried unsuccessfully to get him out, but he pushed his way in, shut the door behind him and pushed her in the direction of her bed, which was off camera, Pirraglia said.

He heard Liu say both in English and Mandarin, "No. No," Pirraglia said.

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Meng then heard what sounded like two muffled bangs and he didn't hear Liu again, Pirraglia said. He then saw the man lock the door and turn off the lights.

The next time the man appeared on screen – he approached the computer and turned it off — he was naked from the waist down, Pirraglia said.