Graphic evidence forced a juror to flee the courtroom during the Tesfai Negasi murder trial Friday.

Negasi, 54, is accused of killing, then dismembering his wife Selamawit Negasi, 46, on July 5, 2009.

Earlier Friday. the judge warned the eight women and four men on the jury that some of the evidence could prove emotionally difficult.

The province's chief medical examiner Dr. Graeme Dowling apologized in advance for what he called the extremely bothersome and disturbing autopsy photos.

Dowling testified he was not sure exactly how Selamawit Negasi died. But he said her skull had been crushed, possibly by a heavy mallet. He also testified that based on the injuries, the victim could have been strangled, smothered or drowned.

He also testified the mother of four would have been dismembered after she was dead.

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Dr. Graeme Dowling, shown here outside the Edmonton courthouse, apologized to jurors Friday for the disturbing autopsy photos they had to view. (CBC)

The testimony was interrupted when one of the jurors abruptly stood up and left — clearly overcome by the disturbing photos.

"This type of death, this type of case is upsetting to everyone," Dowling later said outside the courtroom. "For the family it's horrible. And for anyone who has to listen to the facts it's difficult.

"The type of injury that was present would be similar to what one would see if a motor vehicle passed over a person's head."

Earlier in the trial, jurors heard that Negasi drove to Edmonton police headquarters where he confessed the slaying to police.

"I killed my wife," he said on a recording.

When officers came outside, Negasi told them his wife's body was in the car. When they opened the trunk, officers found body parts along with a handsaw and a knife with a rusty blade.

Jurors heard testimony Friday afternoon from Edmonton Police Sgt. Devin Laforce, a crime scene investigator.

Testing showed large amounts of blood had been spilled in the master bedroom and adjoining bathroom, he said. Police found a positive luminol reaction down the bathtub and shower drains.

Laforce said it appeared the victim's body had likely been dismembered in the bathroom.