Mark Sanfratello has pleaded guilty to the 1983 murder of his girlfriend Teresa Peroni, ending a 43-year cold case investigation in Washington State. Sanfratello received a 20-year prison sentence for the killing.

The breakthrough in the decades-old case came through new forensic evidence that linked Sanfratello to Peroni's death. Investigators were able to use advanced DNA analysis techniques to connect him to the crime after more than four decades.

Peroni was found dead in 1983, but the case had remained unsolved for years despite ongoing investigation efforts. The case represents one of numerous cold cases that have been resolved in recent years through improvements in forensic technology and DNA analysis capabilities.

Sanfratello's guilty plea brings closure to a case that had remained open since the early 1980s. The resolution demonstrates how modern investigative techniques can provide answers in long-unsolved criminal cases, even when decades have passed since the original crime occurred.