For nearly 37 years, she was known as Buckskin Girl—a young, anonymous murder victim found outside Dayton, Ohio, wearing a deer-hide poncho. Then, in April 2018, police announced that the mystery of her identity had been solved. Her name was Marcia L. King, and she had been identified by linking a snippet of her DNA to one of her cousins.

It was one of the first high-profile cases in which this investigative method had been used to identify an unclaimed body. Two weeks after King’s name was revealed, police in California announced that they’d used similar techniques to track down the Golden State Killer. Suddenly, the combination of genetic sampling, genealogical research, and old-fashioned gumshoeing was hailed as a revolutionary breakthrough that would crack hundreds of cold cases.

Since then, forensic genetic genealogy has cleared more than 400 cases in the U.S. Yet this detective work is complex and time-consuming. While King was IDed after just a few hours of sleuthing, most cases take much longer. On average,…