One of two men accused of killing a young Toronto woman five years ago promised in a text message to "hurt her" and "make her leave," court heard Wednesday.

Jim Falconer, a recently retired detective sergeant from the Ontario Provincial Police's technical crimes unit, testified in the trial of Dellen Millard and Mark Smich, who are charged with first-degree murder in the presumed death of Laura Babcock.

It took Falconer and a team of forensic officers months to comb through troves of data retrieved from three computers seized by police at Millard's home in 2013. The data included backup copies from three of Millard's iPhones and Smich's iPad, hundreds of photos, videos and text messages.

Millard and his girlfriend, Christina Noudga, sent late night and early morning messages back and forth discussing Babcock at length a few months before Babcock vanished in the summer of 2012.

In a series of messages Falconer read in court, the couple compared Babcock to the herpes virus, in that it never goes away.

"For every turn of kindness you showed her, she took it and threw it in my face making me discouraged, f--- she's like a virus. Like herpes. She's always there but only shows up once (in) a while with a whole lot of annoying lesions!" Noudga wrote to Millard on April 17, 2012.

"There's a difference, herpes you can't really hurt or get rid of, it just feeds off you until you die. First I'm going to hurt her. Then I'll make her leave," Millard responded.

Court has heard that Millard was sleeping with both Babcock and Noudga at the same time, leaving bad blood between the two women.

Millard, who is representing himself, has said he didn't care about the brewing animosity, but the Crown alleges he and Smich killed Babcock because she had become a problem for Millard.

They contend Millard and Smich killed Babcock then burned her body in a large incinerator that was later found on Millard's farm in North Dumfries.

Millard, 32, of Toronto, and Smich, 30, of Oakville, Ont., have pleaded not guilty to the charges.

"I don't know why, but when you say things like 'from her dealings with you...I'm going to hurt her...make her leave...remove her from our lives' I feel really loved and all warm on the inside," Noudga wrote to Millard a few days later on April 19, 2012.

Many in the packed courtroom gasped. Babcock's mother, Linda, shook her head, then stared at Millard.

"Nothing like sinister insinuation to make you feel all warm & fuzzy," Millard wrote back to Noudga.

A few months prior, Babcock, in the throes of mental health issues, professed her love for Millard in several text messages.

In one text sent at 1:34 a.m. on Feb. 9 2012, Babcock wrote to Millard: "u already know but I really do love you. And u don't need to respond."

"Love is a wonderful & terrible thing. I am thankful for your feelings. It would be better for you if you found someone else to love," Millard wrote back.

Falconer also went through a series of texts showing Millard had someone named "Shaner" build a homemade incinerator for him.

On May 28, 2012, Shaner sent images of the incinerator to Millard. It looked like a homemade rocket with several green oil barrels stacked on top of each other.

Millard sent the same image to Smich in a text.

"Do u have any bones for tonight? Or we just putting it together," Smich wrote to Millard.

"I will have something," Millard wrote back.

"Maybe we should get me a dog. Or your neighbors dog," Smich wrote.

"Lol," Millard texted back.

Falconer, who the judge described as the trial's "most substantial witness," will continue his testimony Thursday.