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MONTREAL -- Luka Rocco Magnotta's lawyer grilled the forensic pathologist who examined the remains of victim Jun Lin, taking him to task for not having watched the so-called murder video before coming to his conclusions.

Defence attorney Luc Leclair suggested Friday that Yann Daze's analysis was flawed because he didn't watch the video, going as far as calling him "incompetent" for not doing so.

Daze defended his approach and said his opinions must be formed on what he sees in the lab, not on a video.

The witness repeated that he didn't want to taint his findings and that he saw enough "disgusting things" in his line of work. On Friday, he clarified that he wasn't calling the video in question disgusting, as he hadn't seen it.

The 32-year-old Magnotta has pleaded not guilty to five charges in the murder and dismemberment of Chinese engineering student Jun Lin in late May 2012.

Magnotta has admitted to the underlying acts he's accused of in Lin's death, but is arguing he is not criminally responsible because of mental disorder.

Daze said Friday there were no defensive wounds found on Lin's body, indicating the victim didn't put up any kind of a fight.

The witness had testified that two drugs were found in Lin's body: the sleep drug Temazepam and Benadryl, an over-the-counter allergy medication.

Daze said the autopsy was complicated given the dismemberment of the body as well as the advanced state of decomposition.

The forensic pathologist concluded that Lin's throat was slit with a sharp object like a knife, which was the probable cause of his death. He was unable to determine whether numerous blows to the victim's head were inflicted before or after death.

The wounds were caused using four different weapons -- a hammer, a screwdriver, a small electric saw and a knife -- items that were later found in the trash behind Magnotta's apartment building.

In an often testy cross-examination Friday, the defence dramatically showed off some of the weapons believed used in Lin's slaying.

Leclair plugged in and turned on the handheld oscillating grinder saw briefly, the sound of its loud, screeching blade echoing through the courtroom.

The lawyer then produced the hammer, smashing it hard on the table during a question about the use of force. Leclair challenged Daze's finding that Lin's temple had been struck numerous times with the hammer. The defence attorney suggested one blow, with sufficient force, could have had the same impact.

Daze called Leclair's assertion "simplistic" and maintained his testimony: the victim had been struck too many times to count and one blow could not have inflicted the type of damage he viewed.

The pathologist said he has conducted more than 1,100 autopsies, about 10 of them involving hammers as weapons.

The jury heard the saw was only examined in late September by Daze. It initially was not in working order when discovered by police, but a ballistics expert managed to fix it.

Leclair took issue with the fact it was repaired and said it should have been examined in its original state.

Daze said that would have changed little -- his findings were based on the characteristics of the saw, not if it was operational.

As the instruments were shown to the court, an irked Daze reminded Leclair repeatedly he was contaminating the courtroom and the exhibits by manipulating the tools.

On a number of occasions, Daze refused to manipulate the items himself and objected to them being displayed in open court.

"I'm not favourable to showing exhibits in court like this, but if I have to, I will," Daze said. He asked that the water pitcher before him be changed for fear of contamination.

On Thursday, Daze testified that Lin sustained 73 post-mortem wounds in the upper body, abdomen and back. Parts of Lin's left buttocks were missing and there were also lacerations to his anus.

The victim's body was cut into a total of 10 pieces.

The charges against Magnotta are first-degree murder; criminally harassing Prime Minister Stephen Harper and other members of Parliament; mailing obscene and indecent material; committing an indignity to a body; and publishing obscene materials.

The trial resumes Tuesday with a new witness.