Why solving cold case killings just got much harder for police

Sean McCowan carries the burden on his wrist.

The number of days — 14,219 — etched in silver on a bracelet. A constant reminder of the agonizing, 39-year wait between the December 1983 murder of his sister, Erin Gilmour, and the 2022 arrest of the man who killed her. 

"Joy isn't the right word. It's just relief," McCowan said, remembering the "we got him" call from a Toronto police detective. "I'm a lighter person as a result because I've got the answers." 

Cracking cold case killings, sometimes decades after the fact, has always been a difficult task for police. But the challenge has recently become much steeper. That's because of new limits on their best tool — genetic genealogy, which uses tiny snippets of DNA to track down killers via distant family relations. 

The U.S.-based website Ancestry.com is the world's largest repository of public genealogical records, pulling together birth, death, marriage, immigration and other documents from across the globe. And it has become a go-to-source for police forces seeking to map out family trees.

But a recent update and clarification to the company's terms of service now explicitly bans law enforcement from accessing the paid-subscription site without first obtaining a court order, making detectives' research process harder.

"It's basically like a Google search for genealogy … a one-stop shop to get the information that we needed," said Acting Det. Sgt. Steve Smith, head of the Toronto Police Service cold case unit, which does genetic genealogy research for 17 forces across Ontario as well as working its own files.

"We can still find the open source data. It's just that it will take us 10, 12, 15 searches instead of one. So it's going to expand the time it takes us to solve these cases."

According to a recent New York Times tally, genetic genealogy has helped solve more than 1,400 cold cases since it was first used to identify California's Golden State Killer in 2018. But it's often a painstaking process — even with access to Ancestry's data. 

Take the case of Erin Gilmour. The 22-year-old Torontonian was sexually assaulted and stabbed to death in her Yorkville apartment a few days before Christmas 1983.

Investigative leads petered out, and it wasn't until 17 years later that police were able to use DNA from the scene to link the crime to another murder — the August 1983 assault and stabbing of Susan Tice, 45, in her apartment in Toronto's Annex neighbourhood. Tests proved the same man carried out both killings, but there was no match in law enforcement databases and his identity remained unknown.

Progress finally came in late 2019, when Toronto police submitted the DNA samples to a lab in Texas for advanced, new tests.

Single nucleotide polymorphism (SNIP) analysis provides far more detail than the standard short tandem repeat (STR) tests for 22 DNA markers, mapping genes for things like hair colour, eye colour and most importantly, ancestry.

Toronto police took those results and uploaded them to GEDMatch and FamilyTreeDNA, two websites where people willingly share their DNA profiles, in hopes of finding some sort of family relation to the killer.