So many white people have bought into consumer genetic testing that it’s now possible for law enforcement agencies to use genetic data to hunt down virtually anyone of European descent — even if they’ve never spit in a trendy tube themselves — by tracking their distant relatives who have already shared their results from companies like 23andMe and Ancestry.com. According to a study published in the academic journal Science, it’s not all that difficult to find someone in the U.S. based on existing, easily accessible ancestral data. And it’s all thanks to the 15 million people who have voluntarily submitted to the autosomal genetic tests. After all, that’s how police found and finally arrested the so-called “Golden State Killer,” Joseph James DeAngelo, in April — by matching DNA from decades-old crime scenes to the online DNA database run by GEDmatch, a Florida-based, open-access genealogy website. Through that new, inexpensive technology, the Sacramento County Sheriff’s Department got a sense of DeAngelo’s family tree and narrowed down their suspect profile to an older, 5-foot-11-inch white male. Since then, at least 13 cases have been reportedly solved through such long-range familial searches, according to the study, which was published Thursday. With that in mind, the researchers analyzed a dataset of 1.28 million people who used a genetic testing kit with a direct-to-consumer provider, and found that about 60 percent of searches for people of European descent resulted in a third cousin or closer match, otherwise indicating a shared ancestor that would offer a person’s identification upon further research.
“Each individual in the database is like a beacon of genetic information, and this beacon illuminates hundreds of individuals — distant relatives connected to this person via their family tree,” Yaniv Erlich, the chief science officer of the genetics company MyHeritage and lead author of the Science study, told the Washington Post.
After spotting a target’s third or second cousin, researchers reduced their searches based on a 10-year age range, biological sex and the assumption that a potential criminal would still be within 100 miles of their crime scene. They were able to prune a pool of approximately 850 people down to 16 or 17 individuals, which they could then profile in “manual inspection.” If they knew a specific birth year, they could usually get it down to one or two people.
Seventy-five percent of those 1.28 million people were of a northern European genetic background, according to the study. Should their dataset reach three million U.S. people of that descent — or about two percent of the target population — the researchers predict that about “99% of the people of this ethnicity would have at least a single 3rd cousin match and over 65% are expected to have at least one 2nd cousin match.” Since DNA testing kits are a hot holiday gift, that future isn't all that far off.
The researchers note that such availability isn’t always a positive thing, though, and could pose serious privacy risks. For example, the researchers used the same methods to identify an otherwise anonymous woman whose DNA was stored within the National Institutes of Health research database known as the 1,000 Genomes Project. The project, they say, was time-consuming, requiring “a full day of work.”
“While policymakers and the general public may be in favor of such enhanced forensic capabilities for solving crimes, it relies on databases and services that are open to everyone,” they wrote. “Thus, the same technique could also be exploited for harmful purposes, such as re-identification of research subjects from their genetic data.”
Cover image: A reporter examines a 23andMe Inc. DNA genetic testing kit in Oakland, California, U.S., on Friday, June 8, 2018. The direct-to-consumer genetic-testing industry has grown from some $15 million in sales in 2010 to more than $99 million in 2017, and is projected to reach $310 million by 2022, according to one industry estimate. Photographer: Cayce Clifford/Bloomberg via Getty Images