SKOWHEGAN — The man accused of killing Rita St. Peter was a suspect for more than 31 years, but it wasn’t until recently that police matched his DNA with semen found at the scene of her death in Anson, a prosecutor said Monday.

The state released new information in the case involving Jay Mercier, 56, of Industry, who faces a murder charge in the killing of St. Peter on July 5, 1980, off Campground Road.

During a hearing in Somerset County Superior Court, Assistant Attorney General Andrew Benson said there is evidence that Mercier sexually assaulted St. Peter, bludgeoned her on the head with a weapon akin to a tire iron and partially ran her over with his pickup truck. The account is also described in a five-page affidavit by Maine State Police Detective Bryant Jacques.

Benson pointed to further evidence Monday in an effort to keep Mercier in jail until his trial.

He told Justice John Nivison that at the time of St. Peter’s death, Mercier had two sets of tires on his pickup, with the front tires different from the back tires. Those unique tires matched the tracks on St. Peter’s body at the scene of the crime, Benson said.

Defense Attorney John Alsop argued that Mercier should be held under house arrest until his trial.

“He is as bail-worthy a candidate as I have seen,” Alsop said, referring to the fact that police have interviewed Mercier many times and he has never fled. He also said that sex is not proof of Mercier killing St. Peter.

Nivison ultimately sided with the state and ordered Mercier to be held without bail until his trial.

Mercier said nothing and remained expressionless throughout the hearing.

Afterward, St. Peter’s sister, Christine Belangia of Weld, stood outside the courtroom with four other family members. “I’m just glad it went the way it went,” she said.

Benson and Alsop said they were not surprised by the judge’s decision, because it’s not unusual for a murder suspect to remain in jail pending trial.

St. Peter, who was killed when she was 20, was last seen alive during the late evening of July 4, 1980, near the bridge leading from Madison to Anson. When her body was found on a field road the next morning, she was on her back. Her clothing was ripped, and her face, her head and the ground were covered in blood, according to Jacques’ affidavit, which was filed Monday and contains photographs of the body.

When police arrived, there was one distinct tire track in the dirt. Dr. Henry Ryan, Maine’s chief medical examiner at the time, determined that St. Peter had sustained multiple internal and external injuries to the head and torso, including skull and rib fractures, the affidavit says. He attributed the cause of death to injuries caused by being run over and hit on the head with a weapon.

People told police at the time that St. Peter was intoxicated when she left the Depot bar in Madison and made her way toward Anson, according to the affidavit. Some people told police they saw Mercier alone in his truck; others said they noticed his truck in the area around the time St. Peter was leaving the bar.

Mercier was a suspect from the beginning. The day after St. Peter’s body was found, he signed a consent form to allow police to search his 1980 GMC pickup, the affidavit says. Barry DeLong, an investigating officer then and the current sheriff of Somerset County, drove the truck to a mechanic in Madison to get inked prints of the tires. In December 2005, a forensic scientist matched the impressions to those at the crime scene, according to the document.

On Jan. 15, 2010, Detective Jacques met with Mercier outside his home in Industry to talk to him about St. Peter. During the conversation, Mercier smoked cigarettes and threw them near the road, court papers say. At the end of their talk, Jacques picked up a cigarette butt and took it to the state crime laboratory.

Although Mercier told police he never had sex with St. Peter, the DNA on the cigarette butt matched semen found in her, the affidavit says.

Police got a warrant for another DNA sample, and the second sample confirmed the DNA match.

When police asked Mercier what he was doing the day of St. Peter’s death, “he admitted that he had been consuming alcohol throughout the day and night and stated that he could drive pretty well when he was drunk,” the affidavit says.

In Mercier’s defense, Alsop said the state does not have an airtight case. In particular, he said he wants to know exactly where the evidence has been for the last 31 years and why the tire impression evidence was not completed until 25 years after the crime.

If people saw Mercier near the Depot bar on the night of St. Peter’s death, Alsop said, it’s because he lived nearby.

Morning Sentinel Staff Writer Erin Rhoda can be contacted at 612-2368 or at: [email protected]