TORONTO -- An investigative technique widely used in the United States but still new to Canada helped police solve the murder of Christine Jessop, a nine-year-old girl who was abducted, sexually assaulted and murdered 36 years ago.

Toronto police had a key piece of evidence -- a semen sample on Jessop’s underwear -- but until recently they didn’t have a DNA match. So they turned to the science of genetic genealogy, which combines DNA analysis and family tree research.

Genetic genealogy uses existing DNA data to provide a possible family tree from a human sample. Rather than one suspect, the approach digs up a broad family lineage, from parents and siblings to distant cousins. It’s then up to investigators to use classic investigative tools, such as combing through historical records, obituaries, social media or other channels to winnow their search.

In this case, Toronto police sent the DNA sample down to a laboratory in the United States, because there are currently no Canadian labs that specialize in genetic genealogy.

Staff Supt. Peter Code noted that, while the findings from the genetic genealogy test were not considered evidence, they helped investigators create two potential family trees.

“After extensively combing through detailed reports and documents, the second family tree produced Calvin Hoover,” Code said at a press conference on Thursday.

Hoover was 28 when he killed Jessop, police said, adding that he and his wife had a “neighbour acquaintance” relationship at the time of Jessop's death and that he may have worked with her father.

Hoover died five years ago.

Genetic genealogy is not widely used in Canada, but this case could change that, according to Sean Sparling, a former police chief in Sault Ste. Marie, Ont., and president of the Investigative Solutions Network.

“This is going to be a new emerging technology for Canadian law enforcement. You’re going to see a lot of cold case units where they have unsolved homicides, unsolved serial rapist cases, they’re going to be turning to this technology,” Sparling told CTV News Channel on Thursday.

In the United States, genetic genealogy has already helped crack several decades-old cold cases. Last year, forensic genealogists tracked down the identity of a woman killed near a Lake Tahoe hiking trail in 1982 and the identity of her killer.

In California, a man who was falsely accused of murdering a newspaper columnist and spent 14 years in prison was exonerated thanks to the technology. His case marked the second time in the U.S. that genetic genealogy helped prove someone innocent.

The work to finally track down Jessop’s killer involved “excellent police work,” said CTV News Public Safety Analyst Chris Lewis. But he said there are some lingering questions about how Toronto police accessed DNA information that led them to Hoover.

“The police just don’t have the DNA profiles of family members of suspects in their labs. Unless those people were charged with an offence that would require them to give a DNA sample, so somehow or another they’ve linked it through family members’ DNA, which may well have come from some private company like," he said.

The particulars of the case may never be fully known, Lewis said, because the case won’t head to trial.

“So there will never be a matter of it being tried and true and proven in court under that scrutiny. But it was enough for them to be able to close the file and give closure to the Jessop family,” he said.

With files from CTV Toronto’s Sean Davidson