SKOWHEGAN – A witness in the trial of a man who is charged with killing a woman more than three decades ago described the gruesome discovery of her body on a road in Anson on Thursday.

James Ross, a former game warden, testified that the body of Rita St. Peter was found partially clothed, and that a pool of blood and injury to her face suggested she had been run over.

Ross said the body was discovered by a young man who was leading a team of horses.

St. Peter’s family members were in the courtroom as photographs of the crime scene were projected onto a screen in Somerset County Superior Court.

Jay Mercier, 57, of Industry is accused of beating the 20-year-old woman with a heavy instrument, and then running over her with a truck.

Investigators have said Mercier was a suspect in St. Peter’s murder from the start but they didn’t have enough evidence to charge him.

DNA from a cigarette butt linked to Mercier matched DNA from semen recovered from St. Peter’s body, leading to Mercier’s arrest last year.

Defense attorney John Martin told jurors in his opening statement that DNA evidence may show that Mercier and St. Peter had sex, but that doesn’t prove he killed her.

St. Peter was last seen leaving a tavern in Madison late on July 4, 1980, and Mercier was seen in the same area that night, said Assistant Attorney General Andrew Benson. Tire tracks from the scene matched the pickup truck he was driving.

Police collected Mercier’s DNA after he discarded a cigarette in the road while being interviewed by police in 2010.