All of the evidence against Brian Dickson was heard in just six days, as the Crown announced the biologist with the Centre of Forensic Sciences was their last witness. The defence called no evidence.
Dickson has pleaded not guilty to first-degree murder in the death Qian Liu, a 23-year-old student from China, whose mostly naked body was found face down on the floor of her off-campus basement apartment on April 15, 2011.
Liu had been chatting via webcam with her ex-boyfriend in China when he saw a man force his way into her room, he testified. There was a struggle and Liu was pushed down, the ex-boyfriend Xian Meng testified. She was saying "no," but after he heard two muffled bangs there were no more sounds from Liu, Meng said.
After a period of silence he heard heavy breathing then the lower half of a naked man appeared in front of the webcam and the computer was turned off, Meng testified.
Dickson should instead be found guilty of manslaughter, his lawyer has told the jury.
He was a tenant in the same building as Liu, though he wasn't a current York student. He had been taking classes there on and off since 2000, but was at that time working at a job handing out flyers, Dickson told police.
Melissa Kell, a forensic biologist with the Centre of Forensic Sciences, testified Tuesday that semen was found on Liu's abdomen and groin area and male DNA was found under her fingernails and on her breasts.
Dickson could not be excluded as the source of the semen and DNA, with astronomical probabilities that a random person would match the same profile, Kell said.
The odds that male DNA under Liu's fingernails came from someone else are one in 17 billion, Kell testified. The odds that DNA in bodily fluid — possibly semen or saliva — on Lius' breasts came from someone else are one in 25 trillion, Kell said.
The odds that semen found on Liu's abdomen and groin area were from someone else are one in 2.7 quintillion.
Blood was also found on a blue T-shirt belonging to Dickson, Kell said. Liu could not be excluded as the source, and the odds that it came from someone else are one in 140 quadrillion, she said.
No DNA other than Liu's was found inside her mouth or genitals, the jury heard.
The jury heard Tuesday morning from the third pathologist to testify at the trial. Dr. Kristopher Cunningham, a cardiac pathologist, backed up the opinion of the other two forensic pathologists — that Liu's heart did not cause her death.
Dickson's lawyer, Robert Nuttall, has put a number of scenarios about heart abnormalities, diseases and the heart suddenly stopping due to a blow to the chest.
Cunningham testified that he found no evidence to suggest any of the above scenarios.
Closing arguments are scheduled for Friday.