RIVERTON — With a sworn jury and a team of attorneys, Mario Mills has begun his trial for first degree murder.

Mills is charged with shooting his friend, Trevor Bartlett, in the head after a night of drinking in Mills' garage over the night of March 25-26, 2020. The defendant told Riverton Police Department detective James Donahue that the pair were arguing about suicide: Bartlett would contemplate suicide, and Mills reportedly told him to just do it.

“I think you’re going to learn from the evidence,” began Fremont County Attorney Patrick LeBrun during his opening statement in Fremont County District Court in Lander, “that Trevor, although a longtime friend of the Mills family, and a person they probably genuinely cared for, was a ‘pain in the neck.’

“He was needy, he was an alcoholic, he was in and out of jail for alcohol-related offenses.

“But,” the prosecutor continued, “he was also a human being, who was killed by Mario Mills, and Mario Mills did not need to do that.

“He had a choice, and he chose to kill.”

LeBrun said that as Mills met Donahue at the Riverton Police Department for his scheduled interview, evidence was still emerging from the scene and surrounding areas.

“Unbeknownst to Mr. Mills, it had become apparent to detective Donahue and everyone else involved that Trevor had not committed suicide. Rather, he’d been shot in the head by someone else, and left sitting in the same chair.”

Also during that interview, a suspicious bag of clothing containing sweat pants, shoes, some hoodies and rubber surgical gloves had been discovered in a dumpster in the alley.

The odds of probability denote that the DNA inside the gloves was Mills'. It was 147 quintillion times likelier to be Mills' DNA than anyone else’s, LeBrun said.

Mills’ defense attorney, Rob Oldham, delivered a 45-minute opening statement in which he previewed nearly every piece of evidence anticipated, and cast the event as a possible euthanasia, culmination of struggle, or suicide.

Oldham spoke as though he was doubtful about the quality of the investigation.

“(Bartlett’s mother) found out he was compiling a list of people who had ‘done him wrong,’” the defense attorney said. “She found out he’d planned to go to Montana and kill some of these people.”

Oldham then rebuked RPD personnel for not interviewing Bartlett’s mother, and for not searching the man’s house for a suicide note or the presumed death list.

“She went to the police station and got ignored.”

Oldham also disbelieved Fremont County Coroner deputy Erin Ivie, saying that her finding of homicide was due to preconceived notions stemming from Mills' confession.

The defendant had yelled “I shot Trevor!” while meeting with Donahue on March 26.

“I’m going to ask her if she changed her opinion…her cause of death because she’d been told my client confessed to murder,” said Oldham.

The attorney has argued throughout case proceedings that Mills was too drunk to give a cognizant interview.

Fremont County Attorney District Court Judge Jason Conder has noted in his case orders that Mills was “alert” and his interview was, therefore, not coerced.

“Listen to how many times Mario says ‘I don’t remember; I just can’t remember,” Oldham told the jury. He then claimed that Donahue “nagged” Mills into confessing.

To the defense, the evidence not collected carries enormous meaning. Oldham said the material under Mills’ fingernails was not collected; nor was gunpowder residue on either man’s hand.

When RPD officer Casey Tadewald arrived on scene, having been told by dispatch, via Mills’ wife, that Bartlett had committed suicide, Mills followed Tadewald into the garage and showed a gun.

Tadewald testified Tuesday morning that Mills entered the bloody garage without his knowledge, appeared behind him, and said “Here’s the gun. I emptied it.”

Tadewald told LeBrun that Mills’ appearance with the .45 Glock in hand was “very surprising.”

“He was holding a firearm… I said ‘set it down and step out of the garage,’” the officer testified.

Another Mills attorney, Don Fuller, implied during his examination of Tadewald that the officer had allowed the scene to be contaminated, and that gun, therefore, lacked value as evidence.

To convict on first-degree murder in Wyoming, the prosecution will have to prove that Mills premeditated Bartlett’s killing with either hatred, ill will or malice.

Oldham claimed that those elements are not found within this case.