Back in 1974 Mary Irene Gency was just 16, when her nude, frozen body was found near the Sportsman's club in North Charleroi, PA, with multiple skull fractures inflicted by heavy object.
But it was only recent advances in DNA technology that allowed them to analyze samples found at the scene that led cops to her killers - her boyfriend of the time Robert Unwin Jr and his best pal David Davioli, both 54.
Davioli, who cops suspected at the time, but had to release through lack of evidence told cops that on the night of the murder the three of them were smoking marijuana.
Then both of them had sex with Gency.
He testified that Mr. Urwin grabbed a tool from the trunk of Mr. Davoli's car and began beating Ms. Gency in the head, before both of them left her for dead.
According to the Pittsburgh Post Gazette he added that he kept silent for 34 years because he feared for his safety and that of his family.
Unwin meanwhile, will be sentenced at a later date.