In the months before she vanished, Laura Babcock was using hard drugs, working as an escort and actively seeking treatment for her mental health issues, the trial of two men accused of killing the Toronto woman has heard.

Babcock has not been seen or heard from since July 2012, and her body has not been found.

The Crown alleges that Dellen Millard, 32, of Toronto, and Mark Smich, 30, of Oakville, Ont., murdered the 23-year-old because she was the odd woman out in a love triangle. Millard was angry that Babcock had told his girlfriend that she was sleeping with him, the Crown alleges.

Prosecutors believe Babcock was killed at Millard's home and her remains were incinerated a few weeks later at his farm near Waterloo, Ont.

Both men have pleaded not guilty to first-degree murder charges.

Babcock had discussed her mental health struggles with various friends in late 2011 and early 2012, court heard Tuesday.

Shawn Lerner, a former boyfriend who had broken up with Babcock months before she disappeared, told police that she suffered from severe depression at times, and was trying to get proper diagnosis for her mental health issues, court heard.

He also testified that Babcock told him in late June she had been working for a short period of time as an escort.

During several hours of cross-examination by Millard, who is representing himself, Lerner said Babcock told him in early 2012 that she had been diagnosed with borderline personality disorder.

"Her attitude was she would pursue treatment for that," Lerner said.

She also struggled with her parents while living at home and was looking for a place to live, he said.

By late June, Babcock had become transient, bouncing from friend to friend along with her small dog, Lacey, Lerner has testified.

Lerner told court he confronted Millard a few weeks after Babcock went missing because her phone bill showed her last eight calls were to him.

Millard questioned Lerner's recollection of events, including a meeting the two men had after Babcock disappeared.

Lerner said that although it's been five years since he met Millard at a coffee shop in Mississauga, Ont., his memory of what he called "probably the most important meeting" of his life is clear.

Millard asked Lerner several questions about the meeting.

"I'm trying to get at your memory, your recollection, sir, you told us you have an average memory," Millard said.

"I've been very explicit about my memory, this was a long time ago, but this was probably the most important meeting of my life and there are things I can remember clearly -- and I remember that clearly," Lerner said.

At that meeting, Millard denied having anything to do with Babcock's disappearance and also denied he had a sexual relationship with Babcock, Lerner said.

"I mentioned that she got into harder drugs, correct?" Millard asked.

"You mentioned cocaine specifically," Lerner said.

"Did I tell you she was looking for a place to stay?" Millard asked.

"Yes," Lerner said.

"Did I tell you that I refused arranging a place to stay for her," Millard asked.

"Yes," Lerner responded.

Millard also asked Lerner about the first time they met, when Lerner invited Millard to Babcock's birthday party at Medieval Times in February 2011. Part of the group, including Lerner and Babcock, ended the night at Millard's condominium in downtown Toronto.

Lerner said he left with a bad impression of Millard, who he said gave Babcock drugs that night.

"Do you know what drug that was?" Millard asked.

"MDMA or ecstasy," Lerner said.

"Correct," Millard said.

Millard returned on several occasions to ask how Lerner felt about him.

At one point Justice Michael Code interjected.

"What he thinks about you is irrelevant to this trial," Code said to Millard.