When Toronto police announced Thursday that they had identified a suspect in the 1984 murder of nine-year-old Christine Jessop, they used a phrase that’s becoming more familiar to followers of cold cases: genetic genealogy.
Investigators say the DNA investigative technique was used to identify Calvin Hoover as the man who sexually assaulted and stabbed Jessop to death all those years ago. Hoover has been dead since 2015 so no charges will be laid.
Supt. Peter Code emphasized that genetic genealogy does not give an exact match, but rather “provides a potential — and I must stress a potential — family lineage” that investigators have to build off.
Yet the technique has been used to solve several decades-old murder cases over the past couple of years, including one of the most notorious serial killers in American history — who pleaded guilty to his crimes after finally being caught.
Here’s how genetic genealogy works and some of the most notable cases where it’s been used.
What is genetic genealogy?
Despite the advancement of DNA evidence-identifying technology, police have still hit roadblocks when it comes to historical cases, particularly if the DNA collected from a crime scene doesn’t match any criminal databases.
That’s where DNA profiles and genetic lineage databases — including public websites like 23andme and GEDmatch — come into play.
Investigators have discovered that by uploading a suspect’s DNA to one of these databases, they can discover and build a family lineage of other known samples that share the same DNA characteristics.
From there, investigators can search through those related names and cross-reference them with their proximity to the crime scene, their relationship to the victim or their family, and more. They can even go further and discover names of other relatives that aren’t in the database at all, but have enough links to the crime to become a suspect.
In the Jessop case, Code said Hoover was “one of the names that came up in two specific families that we saw. Upon review of the investigative file, (Hoover) is a name that we know had a connection to the Jessop family.”
Kenney Jessop, Christine’s brother, told Global News that Hoover’s wife was their father’s co-worker. He said he and her sister would play with Hoover’s children.
Yet because Hoover had already died by suicide years ago, it’s unclear if investigators were able to complete what is often the next step in genetic genealogy investigations: getting a DNA sample from their living suspect. That’s how police in California were finally able to bring a brutal killer to justice.
Catching the Golden State Killer
For decades, detectives both official and amateur had followed thread after thread, trying to find the man who raped over 50 women and killed 13 people across California between 1973 and 1986.
Using DNA evidence from the various crime scenes, investigators turned to GEDmatch and discovered an enormous family tree of possible connections. After narrowing it down over the course of four months, only one name remained: Joseph James DeAngelo.
Police covertly tracked down DeAngelo, a former police officer, and collected DNA samples from used items outside his home in Sacramento County. After they matched exactly with DNA from the crime scenes, DeAngelo was arrested in April 2018.
DeAngelo, now 74, pleaded guilty this year to 13 counts of murder and 13 rape-related charges while admitting to dozens more rapes and burglaries that couldn’t be prosecuted under the statute of limitations.
In August, he was sentenced to life in prison without a chance of parole.
A B.C. couple murdered in Washington state
The very first time genetic genealogy was tested in a courtroom involved the decades-old murder of a young couple from British Columbia.
Tanya Van Cuylenborg, 18, and 20-year-old Jay Cook were travelling from Squamish to Seattle for an overnight trip in November 1987 when they disappeared. Days later, their bodies were found in two different rural areas of Washington state.
In 2018, investigators uploaded DNA from the crime scene to GEDmatch in partnership with Parabon NanoLabs and genetic genealogist CeCe Moore, who has partnered with law enforcement on dozens of cold cases.
A family tree was built linking distant cousins of the suspect and it revealed that the sample must have come from a male child of William and Patricia Talbott.
The couple had only one son: William Earl Talbott II, who was arrested in May 2018 after investigators covertly collected a DNA sample from a used coffee cup and matched it to the crime scene.
Talbott pleaded not guilty and stood trial in 2019. His defence did not challenge the methods that led to Talbott’s arrest, only insisting that the presence of his DNA did not mean he was the killer.
The Washington state jury ultimately found Talbott guilty of both murders and the judge sentenced him to life in prison in July 2019. It was the first time a case involving genetic genealogy had led to a conviction.
While the technique has been used to find suspects in hundreds of additional cases since DeAngelo and Talbott were arrested — even the 1988 death of a newborn baby in California — it has not been without controversy.
Privacy and ethics experts have questioned the use of public databases that average citizens use to search their family history as a law enforcement tool. At issue is whether those users knew their DNA would be searchable in a criminal investigation.
“Those whose genetic identities are being shared online without their knowledge are not aware that they are participating in this landscape and so cannot be said to have accepted its risks,” researchers wrote in PLOS Biology, a medical journal.
“When the police reach through participants to identify their relatives, those relatives also are unknowing and therefore nonconsenting.”
The U.S. Department of Justice moved last year to rein in police use of genealogy websites, issuing new rules that forbid police from creating fake profiles to covertly trace family lineages of their DNA samples. The sites themselves must also notify customers that their data may be used in investigations.
The sites 23andme and Ancestry.com say they will only open their customer DNA databases to law enforcement if they are subpoenaed or issued a warrant.
Despite the concerns and the move to regulate the practice, family members of the victims who have found closure through genetic genealogy advocate for its wider use by law enforcement.
“Society really owes an obligation to these kids, and to itself, to make use of this tool,” said John Van Cuylenborg after the man who killed his sister Tanya, William Talbott, was sentenced to prison.
“We’d be very much the worse off if we don’t take the opportunity to use this technology to make our society a safer place for everyone.”
— With files from Global’s Jessica Patton and the Associated Press