It's a photo that has been on screens and dissected for hours in the courtroom at the Laura Babcock murder trial in Toronto.

The photo shows an animal incinerator, owned by accused killer Dellen Millard, with flames erupting from its inner chamber.

Expert forensics witness Dr. Tracy Rogers testified in court last week that the objects seen burning in that photo look like human bones.

Yet the defence for the two men accused of killing and incinerating the 23-year-old Toronto woman spent a good part of Tuesday trying to cast doubt on that expert opinion.

CBC News has chosen not to publish the photo, which was found on electronic devices that were seized from Millard's home.

Millard, 32, of Toronto, and Mark Smich, 30, of Oakville, Ont., have both pleaded not guilty to first-degree murder.

They are being tried in Ontario Superior Court in Toronto in front of a jury. Millard is representing himself at the trial.

Dellen Millard Mark Smich

Dellen Millard, left, and Mark Smich, right, are accused of first-degree murder in the death of Laura Babcock. (Facebook, Instagram)

Both Millard and lawyers representing Smich pointed out to the jury that the photos that Rogers was working with for the investigation were grainy, pixelated, and less than ideal for a conclusive forensics examination.

No physical remains were recovered in connection with the case, leaving Rogers with just a photo to examine.

"Essentially you're telling us that you can't for certain identify what species these bones came from," Millard said, during his cross-examination. "Correct," Rogers responded.

"You can tell us that this doesn't appear to be fish bones?" Millard asked, at another juncture. "I can tell you that, yes," Rogers said.

Rogers started her testimony Friday afternoon, saying she had examined two photos that were taken back in July 2012.

"I was able to state that the objects in the incinerator appear similar to human bone," Rogers told the jury.

Dellen Millard

Dellen Millard, 32, faces a charge of first-degree murder in Babcock's death. (Court exhibit)

The Crown alleges an animal incinerator called The Eliminator was used to burn Babcock's body after she was killed in July 2012.

Later in the day, court heard from William Penner, who handles equipment sales for TriStar dairy, hog and poultry. That's the Canadian distributor for the company that sells The Eliminator. Penner testified that most of the company's customers use the incinerators for pet cremations, and also sometimes on hog farms.

Penner told the jury that he usually sells about three or four incinerators a year across Canada. He testified that Millard purchased a 500-pound incinerator model in 2012 for $15,424.

The Crown asked him how long it would take to burn 150 pounds of carcass inside The Eliminator.

"Roughly an hour," came his reply.

Babcock the eliminator

The Crown alleges Laura Babcock was burned in this animal incinerator after she was killed in July 2012. (Court exhibit)

"Everything about this machine was done according to the standards and the rules that have to do with these machines, right?" Millard asked in his cross-examination. "That's right," Penner said.

A Toronto police officer also testified today about several large metal drums that were welded together that were seized from Millard's farm.

Court has previously seen evidence in text messages that Millard's mechanic, Shane Schlatman, had a built a homemade incinerator.

Read a recap of today's live blog for more in-depth coverage. On mobile? View the blog here.

adam.carter@cbc.ca