All it takes is a single strand of DNA to solve murder cases where the trail went cold decades ago.
Genetic genealogy, which compares DNA tests to genetic databases to create a reverse family tree to identify a suspect otherwise unknown to investigators, has emerged in recent years as a powerful tool used by law enforcement of the law to close decades-old cold cases – and identify subjects in ongoing investigations.
DNA is extracted from something like a tooth or a fingerprint left on a car door handle and uploaded to a huge database, where it is compared to millions of other DNA profiles for similarities, known as “starting data points”. These points are then used to construct a family tree for each individual.
“We’re looking at the genetic relatives of our unknown sample,” genealogist Misty Gillis, of Identifinders International and BirthParentFinder, told Fox News. “It gives us a list of all the DNA matches that they have, and it tells us how much DNA they share with that person, an estimate of what their relationship to that person might be, whether it’s first cousin, second cousin or a third cousin.”
Gillis continued, “We can use that information to be able to construct and identify who they are.”
Genetic genealogy played a role in finding Bryan Kohberger, left, accused of killing Madison Mogen, Kaylee Goncalves, Xana Kernodle and Ethan Chapin, sources said. (WSU/Instagram)
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This type of DNA analysis is often used in ongoing, ongoing criminal investigations. Sources told Fox News that genetic genealogy played a role in leading Idaho police to Brian Koberger, who is accused of killing four students last November.
But it is also used to solve what Gillis referred to as “the coldest cases,” such as the Boy in the Box murder in 1957 in which a 4-year-old Joseph Zarelli was found dead in a cardboard box in a wooded area. off Susquehanna Street in Philadelphia.

4-year-old Joseph Zarelli was found dead in Philadelphia in 1957. (Philadelphia Police Department)
“It took me about a month and a half to two months to identify his birth mother and then detectives were able to pull records to determine who the birth father was,” she said. “I was able to use his DNA matches that I couldn’t assign to the birth to verify the correct birth father.”
Gillis was also one of two genealogists who identified Harold Dean Clouse and his wife, Tina Linn Clouse, a couple of John and Jane Does who were found dead in the woods near Houston in 1981. Their murder and the search for the lost Their baby was covered extensively on Fox Audio’s podcast, “What About Holly.”
“All we have is our identity and our name … and if someone can be buried with that name and that legacy and that history, that means the world to me,” he said.
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Genetic genealogy was also used in 2018 to identify and arrest Joseph DeAngelo, also known as the Golden State Killer (GSK), decades after he committed dozens of crimes, including murders and rapes across California. Paul Holes, a true-crime podcast host and former Contra Costa County Sheriff’s Office investigator specializing in colds, credited the genetic lineage with helping him and other investigators narrow down a vast field of possibilities in the GSK case.
“We were pretty sure he was born between 1940 and 1960,” Howles told Fox News during a 2021 interview for the Fox Nation documentary and Fox News Audio Podcast “Grim Tide: Hunting the Long Island Serial Killer.”

Genetic genealogy helped identify Harold Dean Clouse and Tina Linn Clouse, a John and Jane Does couple found dead near Houston in 1981. (Identifiers International)
“The common ancestors we used were great, great-grandparents. These were people born in the 1840s, and we built a family tree of thousands,” he said, recalling how they eventually found a break in the case. “And finally, we landed on a branch in California with a small number of … men of the right age. And then, at that point, it’s just ‘Investigation 101.’ Who are these men and could any of them is there someone we should look at closer to being the person in charge?’
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The databases used by genealogists are based on information gleaned from DNA profiles of people who have voluntarily submitted their results to various ancestry tracing companies. Some of these companies have openly shared this information, but others only when subpoenaed.
The idea of a person unwittingly taking a DNA test used to identify a criminal has sparked privacy concerns, something GSK rape victim Kris Pedretti has acknowledged. However, he said it is largely offset by the benefits. He said DeAngelo had “fooled everybody for many decades” and would likely never have been caught if not for the pedigree.
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“I know people are against it and trying to shut it down,” he said. “I hope that never happens because that just protects the bad guys and we have to be proactive to take them down.”
Pedretti continued, “Thank God for DNA because you can’t escape it.”