Your DNA Test Could Crack a Cold Case

Consumer DNA databases are a powerful new tool for police

Illustration: Wenkai Mao

Like most people who take a 23andMe test, Georgia resident Jessi Johnson Still was curious about her ancestry when she spit into a tube and mailed it away to get her DNA analyzed.

After getting her results back, she uploaded her DNA data to a website called GEDmatch that lets people explore their family tree in more detail. She had heard that police used it to catch the suspected Golden State Killer, Joseph James DeAngelo, and she thought maybe her DNA could eventually help solve a crime, too.

Just two months later, in June 2019, Still got an email from a detective in Colorado who was working on a 40-year-old cold case. Police had uploaded crime scene DNA from the suspect to GEDmatch, and Still came up as a distant relative. The detective asked if she’d be willing to share her family tree to narrow down the list of suspects. She immediately agreed to help.

Later that year, Still learned that police had used the information she gave them to arrest and charge James Curtis Clanton — a distant relative Still had never met — with the 1980 murder of Helene Pruszynski, a 21-year-old college student.

“It was really shocking,” Still told OneZero. “It doesn’t even seem real.”

To track down Clanton, the Colorado investigators turned to the same technique police used in the Golden State Killer case, known as genetic genealogy. The rapidly emerging practice allows police to zero in on suspects by combining genetic information from consumer DNA databases with traditional genealogy, which involves building out a person’s family tree using things like public records and obituaries. Because family members — even distant ones — share some DNA, police can use this technique to find relatives that partially match DNA from a crime scene. DeAngelo’s arrest in April 2018 set off a law enforcement frenzy to apply the method to other cold cases. Police have since used it to solve at least 70 violent crimes.

Proponents say genetic genealogy will help make society safer, but the practice complicates a fierce debate over how personal data generated from consumer technology should be used. It also raises privacy risks for individuals and…