It was the case that haunted a small city in Alabama for nearly two decades: Two 17-year-old girls disappeared on the way to a birthday party and were later found shot to death in the trunk of a car.

There was evidence that one of the girls had been sexually assaulted, and investigators collected DNA from the crime scene. The police chased down hundreds of leads over the years, but could not identify a suspect.

Until this month.

On Monday, the Ozark Police Department announced that thanks to the same investigative technique that led to an arrest in the Golden State Killer case, a suspect was in custody. This is at least the fourth case in five days that has been solved using genetic genealogy, as the investigative technique is known. The arrest comes amid dueling efforts to expand and to ban this approach to identifying DNA left at crime scenes.

Chief Marlos Walker of the Police Department said that identifying the crime scene DNA after all these years brought him relief and also surprise: The suspect, Coley McCraney, 45, was a high school classmate. The two even played basketball together, he said.