56-year-old George Shaw of Geneva, Florida was convicted in July of third degree murder and other charges.
Authorities said 14-year-old Barbara Rowan was raped and murdered back in 1984 in Shaw's apartment on Old Lincoln Highway in Bensalem.
Authorities say Rowan lived near Shaw. Her badly decomposed body was found 13 days later in a wooded area between Route 1 and North Drive in Bensalem.
An autopsy determined that Rowan had died of asphyxiation.
The case sat cold for 31 years until October 2015 when Bensalem police and Bucks County detectives charged Shaw and a second suspect, Robert Sanders of Willow Grove.
Sanders, 53, pleaded guilty on February 7, 2017, to two felony counts of hindering apprehension or prosecution.
The Bucks County District Attorney's Office said Sanders admitted to giving false and misleading information that had impeded investigators, and helped Shaw dispose of Rowan's body.
According to authorities, before the arrests, Sanders told investigators that he was in Shaw's apartment at the time Rowan was killed, and that he helped Shaw carry her body from the residence.
He told authorities that they placed the body in the trunk of Shaw's car and transported it to the woods where it eventually was found.
Prosecutors have alleged that Shaw and Sanders were addicts who had gone to Shaw's apartment to use drugs.
Officials said Sanders told police that he saw a girl fitting Rowan's description walk into the bedroom with Shaw, who closed the door behind them. Shortly after, Sanders heard banging noises coming from the bedroom, prosecutors say.
During the alleged assault, authorities said Rowan's father came to the apartment door and asked loudly where his daughter was. When Sanders said he didn't know, the man became upset and threatened to call police, court documents state.
A few minutes after Rowan's father left, Sanders told investigators, Shaw came out of the bedroom, sweating, and saying repeatedly, "I (messed) up."
According to officials, Sanders said he looked into the bedroom and could see the girl lying still on the bed.
Officials say Sanders eventually confided to his brother and a friend about his role, but continued to lie to police until 2015.
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