Wisconsin investigators used genetic genealogy to solve a 50-year-old cold case this week, charging an 84-year-old Minnesota man with killing a woman who was found dead in 1974, authorities said.

Mary K. Schlais, 25, was found dead at an intersection in Spring Brook, Wis., on February 15, 1974, according to the Dunn County Sheriff’s Office. Her death was ruled a homicide, and the initial investigation revealed that she was hitchhiking to an art show in Chicago when she was killed. the agency said.

Jon Miller, of Owatonna, Minn., was arrested Thursday after he “confirmed his involvement” in Schlais’ slaying, according to Dunn County Sheriff Kevin Bygd. He is currently in custody in Steele County, Minn., awaiting extradition to Wisconsin, Bygd said.

“This is a huge win for our agency,” Bygd said at a news conference Friday. It’s the first time the agency has used genetic genealogy to solve a case, the sheriff said.

For decades, detectives from multiple law enforcement agencies assigned to the homicide case have received various leads and tips and conducted interviews, but no “viable” suspects have been identified, according to the sheriff’s office.

Evidence has also been examined and reexamined over the years, but it wasn’t until the agency began working with a team of genetic genealogists at Ramapo College in New Jersey in recent years that investigators were able to identify Miller as a suspect using genetic evidence, the department said.

Forensic genetic genealogy can generate leads for unsolved cases through DNA analysis in addition to traditional genealogy research, according to US Department of Justice.

It combines forensic genetics, or DNA analysis, with conventional genealogy, or one’s family history, for human identification.

“Agencies can spend thousands and thousands of dollars sending DNA samples to private labs all over the country to try to get results, and we had faculty very willing to step up and help us in that process,” Sheriff Bygd said.

Two sheriff’s investigators who worked on the case, Dan Westland and Jason Stocker, said at the news conference that they had spoken with Schlais’ family, who expressed relief and gratitude for the investigation.

The sheriff’s office did not go into detail about what piece of DNA evidence investigators used to solve the case or the genetic genealogy process that led them to the suspect, saying they would leave that up to Ramapo College representatives to address at their Monday news briefing .

The sheriff said investigators were thrown a “curve” while evaluating Miller’s family lineage because he was adopted.

“It takes a lot more work that they’ve put in over the last couple of weeks to try to avoid that curve … We were able to sit with him and let him confirm his involvement in her homicide yesterday.” , he continued.

Westland said that when he and Stocker spoke with Miller on Thursday, he was “pretty calm about what happened.”

“I think it must be quite a relief for him after 50 years of living with this. He must have been on his mind almost every day. You’d think anyone with a conscience would. So, I think he’s done fighting it, personally,” Sheriff Bygd said.

Many of the detectives and former sheriffs who worked the case over the years have passed away, said the sheriff, who added that he was “happy” to tell some of his former colleagues who are still alive that the case has been solved.

“I was sitting in a deer stand when I got a text from the Westland investigator yesterday and it was hard to control my excitement,” Bygd said. “… We went through all the investigators who took this and ran with it and hit a dead end.”

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