A jury bought a defense that an Emery County man, allegedly experiencing methamphetamine-induced psychosis, thought his mother was a demon when he shot and killed her, his attorney said. But not when he did the same to his brother seconds later.
After three hours of deliberation Thursday, the jury handed down guilty verdicts of aggravated murder and manslaughter to Seth Gordon Peterson, concluding a three-day trial in 7th District Court.
The panel also found him guilty of attempted aggravated murder, aggravated robbery and failure to stop at the command of police.
The charges stem from a Nov. 2, 2016, altercation in which the 26-year-old Peterson pointed a rifle at his mother, Susan Peterson, and shot her in the face at a remote ranch in Carbon County, according to court records.
Seth Peterson’s uncle, who witnessed the shooting, according to court documents, said he heard Seth Peterson say, "I just shot my mom in the f---ing face.”
Shortly afterward, Seth Peterson’s brother James Peterson drove toward the mother’s body in a truck. According to court documents, the men’s uncle then heard a second gunshot before seeing Seth Peterson drive away in the truck, his brother fatally wounded.
According to court records, Seth Peterson later approached the owner of the truck, Joseph Scott Feichko, pointed a rifle at his chest and said, “You have to help me hide two bodies."
When Feichko didn’t comply, according to court records, Seth Peterson beat him with a crowbar, then fled in the truck.
Seth Peterson was arrested after officers responded to reports of shots fired and saw him driving away from a farm about 7 miles west of Price, just off State Road 122. He led them on a lengthy pursuit that ended after he crashed the vehicle, court documents state.
Peterson was charged with two counts of aggravated murder, one count of attempted aggravated murder, aggravated robbery and failure to stop at the command of police.
Prosecutors announced in February that they were not seeking the death penalty in the case.
On Thursday, the jury was given the option to find Peterson guilty of manslaughter instead of aggravated murder on both counts.
Defense attorney Rudy Bautista said the manslaughter and aggravated-murder findings are inconsistent, and he plans to explore options to get the aggravated-murder conviction overturned.
At trial, Bautista presented evidence to the jury, showing that Seth Peterson had been using meth for four days straight. He was sleep-deprived and dehydrated when he killed his mother and brother, Bautista said, and was in a state of “meth psychosis.” Seth Peterson thought that his mother and brother were being held captive and that he was confronting two demons, Bautista said.
“It’s not illegal to kill demons,” the lawyer said. “So if he thought he killed demons, he can’t be guilty of aggravated murder.
Peterson had called police that day, saying he was hallucinating and in danger. Police showed up at 2 p.m., Bautista said, and asked Seth Peterson when he last used meth. He denied using drugs, and police called Susan Peterson at 4 p.m. to ask her to come take care of her son, then left the ranch.
Susan Peterson arrived and by 5:30 p.m. had been shot dead.
“Unfortunately in his state, he couldn’t appreciate that it was actually his mother,” Bautista said.
When James Peterson approached the gunman after the first shooting, Seth Peterson asked him who he was and said he didn’t believe the man was his brother, Bautista said.
When Seth Peterson approached Feichko, he told him he needed help hiding the bodies because he “killed two demons,” Bautista said.
Seth Peterson grew up as a member of a fundamentalist Mormon sect that practiced polygamy, though his father was not a polygamist, Bautista said. That background influenced his hallucinations, Bautista said.
“His uncle testified that he believed Seth was possessed by Satan on the day of the shootings,” Bautista said.
Seth Peterson was found guilty of manslaughter in the killing of his mother and aggravated murder in the killing of his brother, findings Bautista said are inconsistent. The killings occurred about 30 seconds apart from each other. If the jury believed intoxication influenced one of the slayings, the lawyer said, that factor should be applied to the other.
“It’s not a light switch,” Bautista said. “If you are impaired by a meth psychosis, that’s not going to disappear in 30 seconds.”
An aggravated-murder conviction holds a minimum sentence of 25 years in prison, while manslaughter holds a sentence of one to 15 years.
During the trial, family members supported Seth Peterson and hoped for manslaughter verdicts. That was the right conviction for both killings, Bautista said.
