The work of unearthing human remains is a delicate task requiring a keen awareness of the environment, such as variations in the colour of the soil.
On Wednesday, police investigators, including a forensic anthropologist, began excavating behind the property.
The dig was triggered weeks ago, when cadaver dogs picked up a scent there.
Scott Fairgrieve, professor of forensic science at Laurentian University and a consultant forensic anthropologist for the province, has worked on similar cases.
Then the excavation starts.
“They’re going to work their way from the edges to the middle. What happens is they usually scrape down an area … and then any soil that is collected from that level, and screen it,” he said.
Once something is found, it’s photographed in situ, then a preliminary identification is completed to determine where in the body the remains come from.
“They will gently remove it from the soil and (it) typically will go into a paper bag,” said Fairgrieve. This prevents the bone from drying out quickly.
Investigators found remains shortly after they began sifting through what police described as compost in a steep ravine directly behind the home. The find follows the discovery, in large garden planters, earlier this year, of human remains belonging to seven victims, alleged to have been killed by McArthur.
During a press scrum near the house Thursday morning, lead homicide investigator Det.-Sgt. Hank Idsinga held off from elaborating on the find until the remains are identified.
He said the excavation will continue “at least until next week.”
In an unusual move, Idsinga permitted members of the media to enter the crime scene.
Former Toronto police detective Mark Valois, now director of academic training at the Canadian Tactical Officers Association, said never in his roughly 13 years as an officer can he recall police giving journalists such access.
“The only thing that came to my mind when I was reading about it was, I guess the investigators weren’t that concerned with contamination of the crime scene,” he said. “For what particular reason, I don’t know.
“I couldn’t answer that.”
Susan Pfeiffer, a professor emeritus of anthropology from the University of Toronto, described the process of recovering human remains. Pfeiffer has been part of archeological digs in Africa and Ontario, working with remains thousands of years old in some cases.
While she is not a forensic anthropologist, the task is something her work involves.
Determining where a burial is requires a trained eye, she said. Disturbances in the soil, variations in the colour of it, are telltale signs there could be something beneath.
“It’s not just looking for the remains; it’s also carefully assessing the space around them,” she said.
The state of the DNA recovered depends on how long the body has been in the ground for and the type of soil it is in.
“A lot of factors around the bone can affect how well the DNA is preserved,” she said. “If it’s in an environment in which bone breaks down quickly, like an acidic soil, for example, you may have more difficult than if it’s a clay-y soil.”
Parts of the body that can be tested for DNA include teeth (preferably molars), a femur, and bones around the inner ear inside a skull, Pfeiffer said.
Trowels, spoons, even bamboo instruments can be used in the dig. It depends on the excavator’s preference and what is being searched for, she said.
“You need to be quite orderly in how you remove the soil, because you want to try to capture a cross-section to indicate where the soil was disrupted. That’s evidence of the creation of a burial,” Pfeiffer said.
Idsinga said it was possible the human remains found may be those of more than one person, or they may be those of one of the seven men whose remains have already been found inside the planters.
McArthur, 66, is charged with first-degree murder in the deaths of Selim Esen, Andrew Kinsman, Dean Lisowick, Soroush Mahmudi, Skandaraj Navaratnam, Abdulbasir Faizi, Kirushnakumar Kanagaratnam and Majeed Kayhan. Their deaths occurred in a period that stretches from 2010 to 2017.
The body of Kayhan, who McArthur is alleged to have killed in October 2012, has not been found.
With files from Wendy Gillis