Riverton Man Who Mercy-Killed Best Friend Gets Probation As Prosecutor Has Change Of Heart

Mario Mills gets a second chance after a judge sentenced him to probation for mercy-killing best friend Trevor Bartlett in 2020. Bartlett's insistent mother said all along that Mills is like another son to her and he didn't act maliciously.

Clair McFarland

June 06, 20236 min read

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(Cowboy State Daily Staff)

A Riverton man convicted of killing his best friend is free, in part because his victim’s mother and a prosecutor both see in him a promising second chance.  

Wyoming District Court Judge Thomas Campbell on Monday sentenced Mario Mills, born in 1982, to five years’ probation, which could revert to an eight- to 15-year prison term if Mills violates the terms of his probation, including by drinking alcohol. The sentence comes after Mills pleaded “no contest” to voluntary manslaughter in March.

“You’re either going to make good on the chance you’ve been given here, or you won’t,” said Campbell. “If you don’t, then the next hearing here will be a short one.”  

Friend Was Suicidal

Mills in March 2020 killed his best friend, Trevor Bartlett, 38, after the pair spent a drunken night playing cribbage, talking and arguing in Mills’ garage in Riverton, according to court documents.  

Bartlett was suicidal and talking of killing people then killing himself, Mills said in his police interview the next morning.  

And Bartlett asked Mills to kill him.  

A jury trial convicted Mills of second-degree murder in March 2021, and Fremont County Judge Jason Conder later sentenced him to spend 20-25 years in prison, essentially the minimum for the charge.  

Mills appealed to the Wyoming Supreme Court, which tossed his conviction in December because Riverton Police Department Detective James Donahue did not read Mills’ Miranda rights to him during the police interview. 

The high court gave Mills the option to go to trial again. But this time the prosecutor would not be able to raise most of that interview as evidence, including Mills’ description of shooting Bartlett with a pistol, unless Mills were to contradict those parts of the interview at a new trial.  

Mills and the prosecutor, Fremont County Attorney Patrick LeBrun, elected not go to trial again. They settled instead on a plea agreement in which LeBrun agreed to seek probation.

Mills spent three years behind bars, including one waiting on a trial and another waiting on his appeal.    


Campbell said heartfelt statements by LeBrun and Bartlett’s mother Destin Walker convinced him to let Mills have his probation sentence. 

“I give great weight to the victim’s mother,” said Campbell. “She takes the position that you’re her family.”  

Walker had urged Campbell to let Mills have probation. She also pleaded with LeBrun to have mercy on Mills before the 2021 trial; and she testified in Mills’ favor at trial, saying he’s like another son to her. 

She spoke with LeBrun again after the high court reversed Mills’ conviction, and her earnestness influenced the prosecutor, he said.  

Campbell called her courageous and her testimony “amazing.”  

It was because of her and because of LeBrun’s change of heart on the case that Campbell agreed to the probation sentence, he said.

But he didn’t do so lightly.  

Campbell called Mills to the podium to speak for himself, saying Mills didn’t have to speak, but this was his chance to do so if he wanted.  

“Trevor Bartlett is dead,” said Campbell. “You’re a combat veteran?” 

“Yes, your honor,” answered Mills, whom the military deployed for two tours, according to his defense attorney Rob Oldham.  

“So you knew before this what ‘dead’ was, didn’t you then?” asked Campbell.  

“Yes, I did, your honor,” said Mills.  

“The permanence and damage done by firearms,” Campbell added.  

This Second Chance 

When Mills approached the podium before Campbell’s questioning, he thanked the judge.  

Mills said he was hopeful for a second chance. He said he plans to spend as much time with his teenage daughter as he can, and emphasized how valued he is at his job, which he got a week after his release from prison.  

Mills has been out on bond for 113 days pending his sentencing hearing, according to court testimony.  

“I’ll give (my daughter) all the extra attention that Trevor would have given her,” said Mills.  

Bartlett had helped to raise the little girl for a few years when Mills was new at being a single father, Oldham said earlier in the hearing.  

Judge Hesitates 

Campbell was torn.  

“There was nothing to thank me for when you came to that podium,” said Campbell, adding that although he was not the trial judge on the case, he has reviewed the trial and has been distressed about the evidence that surfaced during it.  

Campbell also referenced Mills’ criminal history from before Bartlett’s death, involving drunk driving.  

“(That’s) one of the two or three most dangerous categories of individuals that come before judges in America,” said the judge. “They kill way more people than drunks with firearms.”  

Despite his deliberations, Campbell accepted the probation agreement. 

Change Of Heart 

LeBrun has been the case prosecutor for all three years, and those years have changed his approach to it.

“(LeBrun) could have tried this case again standing on his head,” said Campbell, noting again that it’s not the botched police interview keeping Mills out of prison, but LeBrun’s and Walker’s stances on the case.  

LeBrun gave what Campbell called “very moving remarks” in Mills’ favor.  

“I’ll admit that when I initially prosecuted this case in 2020, my view of this case and the facts were different,” said LeBrun.

It has influenced the prosecutor to learn of Mills’ and Bartlett’s close friendship, and the family who loved them both, he said.  

“As I’m standing here, I’m very confident that if Mr. Mills had the opportunity to take what he did back, he would. But I also believe he didn’t have hatred or malice,” he said.

Juries in Wyoming are only supposed to convict on second-degree murder if the defendant acted with malice, according to state law.  

Oldham thanked LeBrun for his “change of heart,” and said that Mills is an excellent dad and a hard worker.  

At Mills’ first sentencing hearing in 2021, Judge Conder said he regretted that no one who testified spoke of obtaining justice for Bartlett.  

Oldham said that struck him at the time.  

“(The judge said) nobody seemed to care about the life of Trevor Bartlett,” the defender recalled. “That stuck in a meaningful way, because Mario loved Mr. Bartlett.” 

Mills agreed to pay about $3,500 in restitution for Bartlett’s cremation and other fees as part of his sentencing.  

Clair McFarland can be reached at clair@cowboystatedaily.com.

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Clair McFarland

Crime and Courts Reporter