DNA experts from Ramapo College of New Jersey helped crack a 50-year-old cold case in Wisconsin.

Mary K. Schlais, of Minneapolis, Minnesota was found dead on a road in Spring Brook, Wisconsin on Feb. 15, 1974. She was believed to be hitchhiking to Chicago.

"Mary was found with multiple stab wounds and her death was ruled a homicide,” said Sgt. Jason Stalker, of the Dunn County Sheriff’s Office.

Only a few pieces of evidence were recovered from the crime scene, including a stocking cap and some hair fibers. Officials said it wasn't enough to identify the killer at the time.

"Prior to DNA technologies, the stocking cap was only able to be used for human hair comparisons,” Stalker said.

Investigators began working with genetic genealogists from Ramapo College in Mahwah in 2022 to find additional leads.

On Nov. 4, on what would have been Schlais's 76th birthday, a suspect in her killing was identified. Officials say he is 84-year-old Jon Miller, of Minnesota. Police interviewed him on Thursday.

“He did inform us that as soon as he had opened the door, he knew why we were there,” said Dan Westland, a Dunn County Sheriff's Office investigator.

Ramapo College experts say it was all thanks to Investigative Genetic Genealogy, or IGG, which uses public DNA information from websites that are used to discover ancestry.

"We build up the family tree to identify common ancestors. From there, we descend the tree using the same kinds of publicly available records and tools until we find the place where the subject may fit into the family tree,” said David Gurney, director of the IGG center at Ramapo College.

They learned that Miller had been adopted. But they ultimately found out who he was through biological cousins, who had no idea he even existed. They agreed to participate in interviews with Dunn County investigators, which led to more information and justice for Schlais.

"I'm happy to report that John K. Miller is in custody here at the Dunn County Jail for her murder, 50 years later,” said Dunn County Sheriff, Kevin Bygd.

Schlais's family members were also present during the news conference.

Ramapo College developed the IGG program in 2022 and helped to solve 17 other cases using DNA matches from public information. They say they're working on about 75 other similar cases.