Christopher Garnier told a police interrogator he watched Catherine Campbell take her final breaths the night he's alleged to have dumped her body near Halifax's Macdonald Bridge. 

In the videotaped interview on Sept. 16, 2015 — hours after the body of Campbell, an off-duty Truro police officer, was found — Halifax Regional Police Det. Const. Michelle Dooks-Fahie asks Garnier what he heard.

"Gasps. Two of them," replied Garnier, who also said he saw blood coming out of her nose.

The Nova Scotia Supreme Court jury in Garnier's second-degree murder trial is slowly making its way through the 9½-hour video of his police interrogation.

When RCMP Cpl. Jody Allison asked Garnier why he didn't help Campbell when he heard her gasping, he replied, "I didn't know what to do."

Garnier, 30, is also charged with interfering with human remains. He has pleaded not guilty to both counts.

Interrogation video

A courtroom sketch shows the scene in the interrogation room at the RCMP detachment in Lower Sackville, N.S., on Sept. 16, 2015. RCMP Cpl. Jody Allison is sitting with his back to the camera, talking to Christopher Garnier after his arrest. (J. Vincent Walsh/For CBC)

The Crown alleges Garnier murdered Campbell in the early-morning hours of Sept. 11, 2015, put her body in a green compost bin and dumped her under the Macdonald Bridge.

Through tears and sniffles, Garnier told Allison he "never wanted anyone to die."

"I'm not a monster," Garnier said.

During the interrogation, ​Garnier said there are gaps in his memory from the evening. He did say he remembered being on a pullout couch with Campbell and she was bleeding.

He said there was blood on the mattress, covering an area about the size of a piece of paper. The mattress has never been found.

Blood was 'all over her face,' says Garnier

"Where was she bleeding from?" said Allison.

"I think her nose. It was all over her face," said Garnier, who at first denied hitting her but then said he may have hit her twice, maybe three times with his fist.

He said he was standing over the bed and Campbell was lying on her back when it happened, but he maintains that he didn't believe they had sex.

The defence has suggested her death was "accidental" and the result of a consensual sexual encounter involving choking.

The jury has watched more than half of the interrogation video over the past three days, which often shows Garnier sobbing and saying he's been told not to talk.

Christopher Garnier arrest shot

A police evidence photo of Christopher Garnier. (Andrew Vaughan/Canadian Press)

That doesn't stop Allison and Dooks-Fahie from keeping up a relentless patter, alternating between cajoling and badgering Garnier to tell his story. On the video, Allison tells Garnier he really doesn't have to talk because the evidence police had collected to that point tells them all they need to know.

When asked by Allison what he would say to the Campbell family, Garnier replied: "I'm sorry for what happened."

When Garnier was arrested, he was driving his girlfriend's car. It had a tarp, work gloves and a gas can in it. It also had a backpack with clothing, toiletries and Garnier's passport.

He told police during the interrogation that the things in the car were there because he wanted to go away. He said he planned to use the tarp as shelter and the gas to start a fire.

DNA evidence

On Tuesday, the court heard from Dr. Gregory Litzenberger, an RCMP DNA expert, who said Campbell's blood was found on a stereo, television, cabinet and the floor of the Halifax apartment where police say she was murdered.

Tests on some fingernail clippings taken from Campbell during the autopsy revealed Campbell's blood. Other clippings showed Campbell and Garnier's DNA, Litzenberger said. He testified the DNA was most likely transferred by friction, such as scratching.

The trial continues Thursday.

CBC reporter Blair Rhodes was live blogging from the trial.