Columbia University's Yaniv Erlich warned a few years back that genetic information people shared could be used to identify them, Science reports.
In 2013, Erlich, then at the Whitehead Institute, and his colleagues reported in Science that they were able to identify about 50 people who participated in a Center for the Study of Human Polymorphisms study based on their de-identified data and Y-STRs — which are linked to surnames — in publicly available genetic genealogy databases. The next year, in Nature Reviews Genetics, he and Princeton University's Arvind Narayanan wrote that websites like GEDmatch that allow for searching autosomal and mitochondrial genotypes could also be used for "genealogical triangulation."
Science writes that their prediction appears to have come true as police officers reportedly used GEDmatch to track down a suspect in the Golden State Killer case. Authorities in California arrested 72-year-old Joseph James DeAngelo in connection with rapes and murders in case last week.
Erlich tells Science that the match police found though GEDmatch likely came from data uploaded by a close relative and that they probably got in touch with that person to learn more about their family tree. "It's not very nice to say no," Erlich tells Science. "Then if you have 20 people on the tree, it's quite trivial to go for the one person you're looking for who is quite old, male, lives in California, and who, some of the victims said, had light colored eyes."
He adds that many users likely don't consider all the ways such databases could be used.