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It sounds like science fiction, but police created this sketch out of a suspect's DNA

Provincial police are hoping to catch Thera Dieleman's killer by releasing a composite sketch of the suspect using a 30-year-old sample of his DNA.

Thera Dieleman was brutally beaten and strangled in her Innerkip home in September 1988

Police have released this composite sketch of Thera Dieleman's suspected killer at the age of 25 (left) and the age of 55 (right). The images were produced using DNA technology. (Ontario Provincial Police)

It sounds like the stuff of science fiction, but Ontario homicide investigators believe they've finally given Thera Dieleman's killer a face, using his own DNA. 

We see this as an opportunity to hopefully stimulate memories- OPP Detective Superintendent Ken Leppert

Ontario Provincial Police on Tuesday published images that are "approximations" of the suspect, almost three decades after the 80-year-old widow was found beaten and strangled to death inside her country home.

OPP Detective Superintendent Ken Leppert said Tuesday that the images were created using DNA believed to be left at the crime scene by the killer on Sept. 16, 1988. 

"This technology wasn't obviously available in 1988," he said. "We see this as an opportunity to hopefully stimulate memories, recollections from back in 1988."

Dieleman lived alone in this country house

Thera Dieleman's residence as it appeared in 1988 along Oxford Road 29, also known as Drumbo Road, east of Innerkip. (OPP)
Back in 1988, Dieleman lived alone in a brown brick house on on Oxford Road 29 in Innerkip, about 20 minutes east of Woodstock.
Thera Dieleman in an undated photo from the OPP. (OPP)

The rural route that was under construction at the time, and the elderly woman was known for giving the local workers refreshments and her two-cents on how the construction job should go. 

Police believe she was murdered during the day. There was no evidence of sexual assault or robbery at the time, but there was evidence that Dieleman tried to fight off her attacker. 

The other clue police had was the fact a flatbed truck was spotted by witnesses sitting in the driveway in her home. It was described as red with white lettering on the doors, dual rear wheels and black headboard protector in the cab. 

Witnesses spotted a truck like this in the driveway

Example of the truck witnesses saw parked outside Thera Dieleman's house around the time of her murder. (OPP)

In 2007, the OPP brought new attention to her case by announcing new technology had allowed investigators to get the DNA of a male suspect. 

That same DNA was used by investigators to create a composite image released Tuesday. 

"We have a DNA sample that we're confident was from the culprit," Leppert said. "We are confident that people from or who lived in the area when this crime occurred may have information on this case.

"We are now providing a great opportunity to bring information forward."

Police got their hands on the image by sending the DNA to Parabon NanoLabs, a company in Virginia that specializes in DNA phenotyping. 

How DNA phenotyping works

The technology uses DNA from biological matter left behind by someone at a crime scene, which could be skin, blood, or even hair.

That DNA is then analyzed and scanned for traits, such as gender, ancestry, skin, eye and hair colour. These variables are then plugged into an algorithm which can produce a composite sketch. 

"By combining these attributes of appearance, a composite sketch was produced depicting what the person of interest may have looked like at 25 years of age," Leppert said. 

"As it has been approximately 30 years since this murder occurred, Parabon has also provided an altered composite sketch with age progression that would depict the person's appearance today."

The technology isn't without controversy and has been criticized for being inaccurate, being susceptible to human bias, error or abuse. 

It might be why Leppert is quick to note that the sketches are merely "approximations" and not 100 per cent accurate.

"The composite sketches produced in this manner are scientific approximations of appearance based on DNA and are not likely to be exact replicas of appearance," he said.

"Environmental factors such as smoking, drinking, diet and other non-environmental factors like facial hair, hairstyle, scars cannot be predicted by DNA analysis and may cause further variation between the subject's predicted and actual appearance."

Whether releasing the image actually works, remains to be seen, but Leppert said if Dieleman's killer is still out there, the OPP want him to know someone is still looking for him. 

"The individual that killed Mrs. Dieleman has had 30 years of freedom and if anything, that makes it of more concern to us as law enforcement that we want to bring that person before the courts and before justice," he said. 

Given the lack of alternatives in the last 30 years, it might also be the best lead police have. 

About the Author

Colin Butler

Video Journalist

Colin Butler is a veteran CBC reporter who's worked in Moncton, Saint John, Fredericton, Toronto, Kitchener-Waterloo, Hamilton and London, Ont. Email: colin.butler@cbc.ca