Investigators in Wisconsin 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 the township of Spring Brook, Wisconsin on February 15, 1974, according to the Dunn County Sheriff’s Office. Her death was ruled a homicide and the initial investigation revealed she had been hitchhiking to an art show in Chicago when she was killed, the agency said.

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

“This is a huge victory for our agency,” Bygd said at a Friday news conference. 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 who were assigned to the homicide case received various leads and tips and conducted interviews, but no “viable” suspects were identified, according to the sheriff’s office.

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

Forensic genetic genealogy can generate leads for unsolved cases by analyzing DNA on top of traditional genealogy research, according to the 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 across the country to try and get results and we had a college very willing to step up and help us with this process,” Sheriff Bygd said.

Two sheriff’s investigators who have been working on the case, Dan Westland and Jason Stocker, said at the news conference they spoke 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 leading them to the suspect, saying they would leave it for Ramapo College representatives to address at their Monday news briefing.