The ex-girlfriend of one of two men accused of murdering a young Toronto woman and burning her remains in a massive animal incinerator saw the large machine in operation the year the alleged killing occurred, a court heard Friday.

Marlena Meneses told a jury she was ordered not to pay attention one night in 2012 as Dellen Millard and Mark Smich worked with the device known as The Eliminator at an aircraft hangar owned by Millard at the Region of Waterloo International Airport.

Meneses -- who started dating Smich in the spring of 2012 -- left to take Millard's dog for a walk and to smoke some marijuana as the two accused operated the machine, court heard. When she walked back to the hangar, she saw the black incinerator outside, she said.

"I saw smoke coming out of it and they had a crackling noise," Meneses said, noting that the machine ran for hours but she didn't know what Millard and Smich were burning.

The Crown alleges Millard and Smich killed Laura Babcock and burned her remains in the incinerator in late July 2012. The two accused have pleaded not guilty to first-degree murder.

Prosecutors allege Babcock, 23, was killed because she was the odd woman out in a love triangle with Millard and his girlfriend, Christina Noudga. Millard, who is representing himself, has said, however, that he didn't care about the animosity between the two women.

Babcock's body has not been found.

Court has heard Millard first got The Eliminator on July 5, 2012. Meneses said she didn't know what an incinerator was when she first saw it in Millard's hangar.

"I asked what an incinerator was for and Mark said it was for farm animals," she said. "I thought it was weird because Dellen didn't have any farm animals."

Court has heard that Millard told others he was going to use the incinerator for a mobile pet cremation business, run with his veterinarian uncle. But his uncle told court that he'd never go into business with his nephew and called the idea "absurd."

Meneses said Millard picked her and Smich up one night -- she didn't say when, just that it was at night and warm outside -- because the two men wanted to test out the incinerator at Millard's farm on Roseville Road in North Dumfries.

"We went to the farm and were there for quite a while trying to test it out for some reason," she said.

"They had me sitting in a car and telling me not to pay attention, put on my headphones, and all of a sudden they come over, saying 'f--- I need a plug!' then leaving the farm and going to the hangar."

Millard and Smich hooked up the mobile incinerator to the back of Millard's truck and drove about 20 minutes to the hangar, Meneses said, where they plugged in the machine. Court has heard the incinerator needed both propane and electricity to operate.

Meneses said she was annoyed because she wanted to go home and, after seeing the incinerator in action, eventually fell asleep in Millard's truck. She woke when they left the hangar and they returned the incinerator to a barn on Millard's farm.

Court has heard that The Eliminator, which Millard and Smich referred to as the "BBQ", wasn't operational until July 23, 2012.

A few days before, Millard texted Smich about a "BBQ mission."

"I won't want Marlena there for that though, think on it," Millard wrote.

"I don't think taking marlena will be a problem. She can wait in the front while we r out back talkin to that girl," Smich wrote back. "If u kno what I mean."

A forensic anthropologist has testified that a photograph of the incinerator's interior shows objects that look like human bones. The incinerator -- which court has heard was capable of cremating a 225-kilogram animal -- was found on Millard's farm.