HALIFAX -- When Const. Catherine Campbell didn't show up for work on Monday, Sept. 14, 2015, officers went to her Dartmouth apartment to look for her.

They found a tidy apartment with the TV on and an alarm clock sounding -- but the petite blonde officer was not there.

What followed was the kind of police procedural work well-known to anyone who watches TV's Law and Order: a series of clues that led them to her body, in thick brush near the Macdonald Bridge in central Halifax, roughly 40 hours later.

By then, they had already zeroed in on Christopher Garnier as a person of interest, according to evidence presented in the ongoing trial's first two weeks.

Police witnesses have revealed to the Nova Scotia Supreme Court jury how Garnier came to their attention -- and of the moment when investigators scrambled to hide as he drove towards the crime scene shortly after Campbell's body was discovered on a steep embankment.

The Crown has alleged Garnier punched and strangled Campbell inside an apartment on McCully Street, a few blocks away from the bridge, and used a green compost bin to dump her body.

Garnier is facing charges of second-degree murder and interfering with a dead body. The trial resumes Monday.

The jury has heard Campbell, 36, was a Truro police officer, but lived an hour away in Dartmouth, across the harbour from Halifax. So when she did not show up for work, the force asked Halifax Regional Police to check on her.

When they didn't find Campbell, officers checked video surveillance cameras from her apartment building, and found footage of her leaving home in the early hours of Friday, Sept. 11.

She never returned.

RCMP Const. Kyle Doane said they learned she took a cab to the Halifax Alehouse, a wood-panelled pub just below Citadel Hill and favoured by a slightly older crowd than the university students who pack other bars in the port city.

Because Campbell lived alone, no one had noticed her missing until the following Monday.

And so it was around 1 a.m. on Tuesday, Sept. 15, that Doane arrived at the bar to review surveillance video.

There on the black and white footage was Campbell, seen kissing and dancing with a brawny man on the previous Friday, before leaving the bar with him around 3:30 a.m.

"At one point they became quite passionate," Doane told the jury on Nov. 22. "The thing that stuck out the most was the point where her legs were wrapped around Mr. Garnier."

Bar staff identified the man as a former Alehouse employee -- Garnier.

The trial has heard that Garnier, who turned 30 on Thursday, had broken up with his girlfriend the previous day, and was starting a new job in the sales department at K & D Pratt Group Inc., an equipment distribution company.

Garnier was now on the police's radar.

On the morning of Sept. 15, he was contacted by Halifax police Det. Const. Scott MacLeod.

MacLeod said that conversation led police to the McCully Street apartment, where Garnier was staying with his friend Mitch Devoe on the evening in question. Investigators later learned a man and woman had been dropped off by a cab in the early hours of the previous Friday.

Next door, RCMP Sgt. Charla Keddy was speaking to an employee of Soma Vein and Laser Clinic, and asked to see surveillance footage from its small back parking lot, which adjoined the back of the McCully Street flat.

On the footage, she saw something unusual.

A blurry figure was seen rolling a compost bin towards the McCully Street apartment shortly before 5 a.m. on Friday, and then away from it.

"You see in the video there's an individual who came out from the area of the back of the (McCully Street home), walking towards the back of Soma," Keddy said on Nov. 23., adding that the man is then seen pulling the compost bin down a driveway towards Agricola Street.

Police prepared to search the McCully Street apartment, even as officers kept Garnier under surveillance.

Halifax police Det. Const. John Mansvelt followed Garnier from his workplace in the Burnside industrial park, to suburban Clayton Park, where Garnier lived, and then to central Halifax.

It was now just after 11 a.m on Tuesday, Sept. 15. Garnier drove to the intersection of Cornwallis and Barrington streets, near the Macdonald Bridge.

Mansvelt said Garnier then stopped at a traffic light but didn't move when it turned green, so Mansvelt passed by to avoid being detected.

He wasn't able to pick up on his trail after that.

About 20 minutes later, officers began to search the McCully flat. They found what they suspected were drops of blood on the floor, wall and baseboard -- and found the mattress was missing from a red pullout couch in the den.

Around 6 p.m., officers fanned out in a grid around the apartment, looking inside compost bins for hours, finding nothing.

Then, a break: Late Tuesday, officers spotted the green bin in brush at the end of a ramp that leads from North Street to Barrington.

A larger search was ordered, and shortly afterward the body of Campbell was found nearby. It was a rare isolated spot in densely populated peninsular Halifax, just up from the dockyards, home to Canada's East Coast navy fleet.

Campbell's body was found face down, her back exposed, partly decomposed, under a box.

As investigators combed for clues, other officers were set up outside the Chadwick Street home in Clayton Park that Garnier shared with his girlfriend, with whom he'd patched things up.

Just before 1 a.m. on Wednesday, Sept. 16, Halifax police Const. David Robertson was sitting in an unmarked vehicle when he saw a man come outside and transfer items from a red Pontiac Grand Prix into a white Ford Edge.

The car drove away, and Robertson alerted the surveillance team that the suspect was on the move.

Halifax police Sgt. Kenneth Burton followed into central Halifax.

And as investigators worked the crime scene under a night sky, police soon realized their suspect was driving towards it.

Halifax police Det. Const. Randy Wood said officers were told to disassemble their gear and hide. "All I saw were headlights," Wood told Garnier's trial on Monday.

But Garnier didn't stop. He returned to Clayton Park, where he was arrested by police, the jury has heard.

Investigators found a green tarp, work gloves, a backpack, yellow rope and tape in the Ford Edge, Burton testified Wednesday.

Nova Scotia's chief medical examiner, Matthew Bowes, testified Tuesday that Campbell died of strangulation, and suffered head injuries including black eyes and a fractured nose.

Garnier's lawyer, Joel Pink, suggested a possible defence in his cross-examination of Bowes. He offered a hypothetical scenario suggesting Campbell died during a consensual sexual encounter after encouraging Garnier to choke her.

On Friday, media were permitted to access exhibits presented at trial earlier this week, including photos of the crime scene, photos of Garnier taken after his arrest, and a short video clip of an individual pulling a compost bin across Barrington Street.

Garnier has pleaded not guilty to the charges.