12/14/2017 03:56 EST | Updated 12/17/2017 03:23 EST

Sexual masochism expert takes stand at murder trial in death of off-duty cop

HALIFAX — Christopher Garnier's defence lawyer attempted Wednesday to bolster his assertion that Const. Catherine Campbell died after asking to be choked, and to explain why his client doesn't remember using a compost bin to dump her body.

Psychiatrist Dr. Stephen Hucker, who was hired by defence lawyer Joel Pink to prepare a report ahead of Garnier's murder trial, was called to the stand in Nova Scotia Supreme Court.

Hucker, who is also an expert in sexual masochism, told the jury that Garnier's account of his sexual encounter with Campbell amounts to him facilitating erotic asphyxiation on the off-duty police officer.

He also said he believes Garnier suffered from acute stress disorder immediately following her death on Sept. 11, 2015.

Hucker was qualified as an expert witness by Justice Joshua Arnold, allowing him to give opinion evidence.

He said he was asked by the defence to answer questions about erotic asphyxiation, its potential risks, and whether PTSD could prevent someone from remembering details of disposing of a body.

Hucker explained that erotic asphyxiation was a form of sexual masochism and a term used to describe asphyxiation for sexual gratification. He said people who practice erotic asphyxiation often do it with a trusting partner and establish a "safe word."

He said harm can be caused during erotic asphyxiation, and that it is possible a person would not give warnings before becoming unconscious because it can happen "within seconds."

"The problem with doing this kind of thing is that people lose consciousness very rapidly," he said.

Hucker said Garnier described symptoms including tunnel vision, loud noises and memory loss following Campbell's death.

"Those symptoms would conform to acute stress disorder," said Hucker.

He said if those symptoms persist, it can develop into PTSD. Hucker said he has diagnosed Garnier with PTSD.

The Crown alleges Garnier punched and strangled the 36-year-old Truro, N.S., police constable after they met at a Halifax bar, and used a compost bin to dispose of her body near Halifax's Macdonald Bridge.

In his opening statement Monday, Pink told the 14-member jury that Campbell died accidentally during "rough sex" that she initiated.

Garnier has told the jury that during sex play, Campbell encouraged him to choke and slap her before she died, but that his memories about the night are fragmented. He said he does not remember disposing of Campbell's body.

Garnier, 30, has pleaded not guilty to second-degree murder and interfering with a dead body.

Hucker said he reviewed evidence in the case, including police interviews, and also interviewed Garnier's girlfriend Brittany Francis, his friend Mitch Devoe, and Garnier on two occasions.

He said he also reviewed the report from Dr. Matthew Bowes, the province's medical examiner, and testimony he gave at Garnier's preliminary inquiry. Bowes had concluded Campbell died of strangulation.

Hucker noted what was missing from Bowes' report was any indication that Campbell had fought for her life, such as injuries to Garnier. The jury has heard that other than some scratches, Garnier had no injuries.

Hucker said that he spoke with Garnier for a total of 6.5 hours on two occasions, and that he showed no signs of agitation and was fully cooperative during the interviews.

"He was dressed in prison clothes. He was neat and tidy and adequately groomed," said Hucker, who interview Garnier in prison.

Garnier did nothing to suggest he had a personality disorder, said Hucker. He said he came across as a quiet, unassuming person, a "people-pleaser" and someone with a tendency to back away from confrontation.

In her opening statement, prosecutor Carla Ball had said: "This case is about a man who loses control."

Hucker was expected to continue testimony Thursday.

Follow (at)AlyThomson on Twitter.