We will find you: DNA search used to nab Golden State Killer can home in on about 60% of white Americans

If you’re white, live in the United States, and a distant relative has uploaded their DNA to a public ancestry database, there’s a good chance an internet sleuth can identify you from a DNA sample you left somewhere. That’s the conclusion of a new study, which finds that by combining an anonymous DNA sample with some basic information such as someone’s rough age, researchers could narrow that person’s identity to fewer than 20 people by starting with a DNA database of 1.3 million individuals.

Such a search could potentially allow the identification of about 60% of white Americans from a DNA sample—even if they have never provided their own DNA to an ancestry database. “In a few years, it’s really going to be everyone,” says study leader Yaniv Erlich, a computational geneticist at Columbia University.

The study was sparked by the April arrest of the alleged “Golden State Killer,” a California man accused of a series of decades-old rapes and murders. To find him—and more than a dozen other criminal suspects since then—law enforcement agencies first test a crime scene DNA sample, which could be old blood, hair, or semen, for hundreds of thousands of DNA markers—signposts along the genome that vary among people, but whose identity in many cases are shared with blood relatives. They then upload the DNA data to GEDmatch, a free online database where anyone can share their data from consumer DNA testing companies such as 23andMe and Ancestry.com to search for relatives who have submitted their DNA. Searching GEDMatch’s nearly 1 million profiles revealed several relatives who were the equivalent to third cousins to the crime scene DNA linked to the Golden State Killer. Other information such as genealogical records, approximate age, and crime locations then allowed the sleuths to home in on a single person.

Read more at https://www.sciencemag.org/news/2018/10/we-will-find-you-dna-search-used...