MONTREAL -- The jurors in Luka Rocco Magnotta's first-degree murder trial were told Monday that none of the evidence gathered in the investigation has enabled police to determine how the accused first met Jun Lin.

"Despite intensive searches ... nothing allows us to establish how they met, when or why," Montreal police Det-Sgt. Claudette Hamlin testified.

That included exhaustive checks of phone records and the online activity of both men, she said.

Police combed through 7,484 photos found on Lin's computer but found none of Magnotta.

The trial resumed Monday with more surveillance video from Magnotta's apartment building that shows him leaving for the last time on May 26, 2012. He can be seen holding a small carry-on suitcase and getting into a taxi that can be spotted in the reflection of the glass door of the building.

That video was captured two days after Lin was seen walking into the building with Magnotta.

Lin was never seen alive again, and Magnotta is spotted discarding items in the trash over two days before leaving the apartment building for good.

Magnotta, 32, has pleaded not guilty to five charges. He insists he is not criminally responsible in the Chinese student's death because of mental disorder.

Lin, 33, was seen on surveillance video wearing a yellow T-shirt, shorts and a baseball cap as he walked nonchalantly into the apartment building with Magnotta at 10:16 p.m. on May 24, 2012.

Just a few hours later, Magnotta was caught on the same cameras, wearing Lin's T-shirt and methodically putting trash in the basement of the building as well as carrying it outside over the next day. Magnotta comes and goes, sometimes stopping to look at his appearance in a mirrored wall in the lobby.

Lin's torso was found on May 29, 2012, stuffed into a suitcase behind Magnotta's apartment building. Other body parts were also discovered in the trash behind the building.

A baseball cap similar to Lin's was found among Magnotta's personal effects when he was arrested in Berlin in early June of that year. Also retrieved was a dark wig that Hamlin said cost $1,700.

On Monday, the jury watched video of another individual who went to Magnotta's apartment a week before Lin's slaying.

That person, who has not been identified by investigators, appears in the first 53 seconds of the so-called murder video the jury has not yet seen.

Hamlin said police became aware of the second individual only in March 2013 while studying the contents of a video camera found in the trash.

That security video shows a man walking into Magnotta's apartment on May 18, 2012, and leaving the next day, with Magnotta holding his arm to help him down the stairs.

While Magnotta admits to causing the acts he's accused of in Lin's death, his lawyer has said his client suffers from schizophrenia and was diagnosed with borderline personality disorder shortly before the slaying.

The Crown contends the killing was planned and deliberate.

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 material.