A man was sentenced to prison after pleading guilty to the four-decade-old cold case slaying of his girlfriend in Oregon. 

Mark Sanfratello, 73, was sentenced Tuesday to 20 years in prison in the death of girlfriend Teresa Peroni in 1983, Oregon Attorney General Dan Rayfield said in a press release. 

"Cases like this remind us of why we don’t give up. It doesn’t matter how many years have passed. If someone took a life, we’re going to keep working until we can hold them accountable."

Peroni, who was 27 years old, was last seen walking into the woods with Sanfratello, her boyfriend at the time, after the pair attended a house party together in Selma.

She was reported missing shortly after, and authorities concluded her disappearance was suspicious.

However, investigators were unable to secure sufficient evidence to bring charges against anyone at the time. 

In 1997, Peroni's skull was found on a nearby private property, but no additional remains were discovered.

Authorities decided to reopen the case in 2024, and investigators "reinterviewed witnesses, collected new DNA evidence and applied modern forensic techniques to build a case against Sanfratello," prosecutors said.  

One year later, in July 2025, Sanfratello was taken into custody in Chico, California, and indicted on first-degree manslaughter charges after being extradited to Oregon, later pleading guilty in Josephine County Circuit Court.

Under the terms of his plea agreement with prosecutors, Sanfratello will serve a minimum of 10 years in prison. 

The Oregon Department of Justice and Sanfratello’s attorney did not immediately respond to Fox News Digital’s request for comment.