OROVILLE, Calif. - 72-year-old Donald Clark is accused of killing Richard Jones Jr., 17, Roland Lowe, 15, and Lowe's mother 46-year-old Colleen Lowe in June of last year.
The three are from the Sacramento area.
Prosecutors said Clark shot and killed them when they showed up on his property in Centerville, then burned the bodies.
Clark's friends said he was frightened of Jones from an earlier dispute.
The trial started off with statements to the jury from both the prosecution and defense.
The prosecution started by calling to the stand the Butte County deputy that responded to the scene and one of the detectives working on the case. They both testified they saw two bodies in the trunk of a car and one in the back seat.
Next, the prosecution called Dr. Thomas Resk, a forensic pathologist, who conducted the autopsies.
First Resk showed Jones' autopsy. He said Jones was killed by a gunshot wound to the torso from close range when he and Clark were fighting over the shotgun Clark had in his hand.
It was revealed Jones' blood level had an extreme amount of carbon monoxide. Resk said based on that information, Jones was alive before the fire.
Resk then showed Roland Lowe's autopsy. Resk said he was shot in the head. Lowe's mother, Colleen was shot in the left side of her chest.
Resk said there was methamphetamine found in her system. Resk testified he found shotgun pellets in all of the victim's bodies.
The trial will continue May 12. The defense says Clark was defending himself that day.