There was evidence that one of the girls had been sexually assaulted, and investigators collected DNA from the crime scene. 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.

The suspect, Coley McCraney, 45, was arrested Friday and has been charged with capital murder and rape in the deaths of Tracie Hawlett and J.B. Beasley, who were found in Beasley’s car on the side of a road on July 3, 1999. They had both been shot in the head.

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.

Hawlett’s mother, Carol Roberts, told The Associated Press that she went numb when she heard an arrest had been made.

“He didn’t have the right to do that,” Roberts said. “I just want to know why.”

Chief Marlos Walker of the Ozark police said he decided to try genetic genealogy shortly after the highly publicized announcement in April that Joseph James DeAngelo, a former police officer, had been charged with the crimes associated with the notorious Golden State Killer.

“It raised my awareness as something we needed to check into,” Walker said in an interview.

The killing of the two teenagers was the obvious case to apply it toward, he said. A double homicide is rare in Ozark, a city of around 15,000 that is about 80 miles south of Montgomery.

“That’s the only case of that nature around here,” Walker said. “This is the crime that shook everyone; not just our city but even wider than that. It’s one of the biggest cases in the state of Alabama.”

Walker hired Parabon, a forensic consulting firm specializing in genetic genealogy, to assist with the case. The first few steps involved in identifying DNA this way are typically the same.

A genetic profile is uploaded to GEDMatch, a genealogy database popular with family history researchers — and, more recently, law enforcement. Then the team of genetic genealogists hopes for a close match, ideally something in the third cousin range. In this case, the relatives were more distant, said CeCe Moore, who leads Parabon’s genetic genealogy team.

“When I looked at this case initially I didn’t think it would be an easy solve,” Moore said. Still, her team was able to build out a family tree, connecting the closer matches to a common ancestor and then filling in the branches with an array of publicly available data.

In the end, it was a lucky coincidence that altered the direction of the investigation. Although the Parabon team was not able to create a probable suspect list, the family tree hinted at several possible surnames. When Walker looked at the list, one stood out: McCraney.

“I recognized that last name,” he said, because he had had a high school classmate with that surname. They graduated the same year and played basketball together.

There was a solid chance that the McCraney he knew could be related to the suspect and that his DNA would help direct the family tree building.

When investigators compared his DNA to the DNA from the crime scene, it appeared to be an exact match, Walker said.

“Like most people, I was surprised,” said Walker, adding he sat frozen in his chair for three hours after learning the news. McCraney had cooperated with the investigation and did not have the type of record or reputation to suggest he had been involved in this type of crime, Walker said.

“But I’ve also been doing this long enough to know that DNA is a solid thing to believe in,” he said. “I didn’t have any reservations when we got a match that this was him.”

McCraney has worked as a truck driver and a preacher, according to The Associated Press. David Harrison, McCraney’s lawyer, told the AP that his client was an outstanding member of the community.

“I’ve been doing this job a long time, and here’s my concern: Social media convicts him before we’ve ever seen the evidence, and that’s troubling to me,” Harrison said.

The announcement from Ozark police comes on the heels of three other cases that were solved using genetic genealogy in the past week, and more than 40 since April, according to Moore.

Questions around the legality of this new practice remain unresolved. In January, a Maryland state lawmaker, Charles Sydnor, introduced a bill that would prevent law enforcement from identifying suspects’ DNA by using relatives in genealogy databases. The bill died within weeks, but it fueled discussion about whether the practice violates people’s privacy. Others have raised concerns about the excessive weight placed on genetic evidence, when there are hundreds of reasons a match may not be an indicator of guilt.

Defenders of the technique say law enforcement is limiting its searches to genealogy databases for which users have explicitly consented to assisting with homicide and sexual assault investigations.

“It’s just a wonderful tool,” Walker said. “I think more agencies will be using it within weeks and months down the road.”

This article originally appeared in The New York Times.