Riverton Man Who Murdered Best Friend Could Now Go Free Because Cops Didn’t Mirandize Him

A Riverton man who spent the last three years behind bars for killing his suicidal best friend could now go free after a failure to Mirandize him led to his conviction being tossed and a new probation-focused plea agreement.

Clair McFarland

March 23, 20235 min read

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(Cowboy State Daily Staff)

A Riverton man who spent the last three years behind bars for killing his suicidal best friend could now go free after a failure to Mirandize him led to his conviction being tossed and a new probation-focused plea agreement.

Mario Mills, who was born in 1982, pleaded “no contest” Thursday to voluntary manslaughter for killing his best friend, Trevor Bartlett. The plea is treated as a guilty plea except that the defendant does not have to give a confession to be convicted. This can spare him from some civil culpability if there are later lawsuits. 

Mills’ plea came after he made a plea agreement this week with Fremont County Attorney Patrick LeBrun. 

LeBrun offered Mills a new sentence of five years’ probation, which would revert to an 8- to 15-year prison term if Mills violates the terms of his probation. The prosecutor also reduced the charge against Mills from murder to voluntary manslaughter. 

“I have spoken to Trevor’s mother,” said LeBrun, referencing Destin Walker. 

Though her son died from Mills’ gunshot, Walker defended Mills adamantly during his trial. Walker described her love for Mills as though he were another son to her, and she insisted he deserves another chance.

“I will say that she has played a major role in this plea agreement,” said LeBrun. “And I do want her to have an opportunity to be present at (Mills’) sentencing.” 

During a raw and tearful police interview the day after Bartlett’s death, Mills told police that Bartlett was determined to die somehow, and had told Mills that he, Bartlett, had a list of people he wanted to kill before he died. 

That’s Unique

Laramie County District Court Judge Thomas Campbell said during Mills’ change of plea hearing Thursday that he does not have to honor LeBrun’s promise of probation and can give a harsher sentence than the agreement defines. 

But if Campbell does choose a harsher sentence, Mills will get another chance to withdraw his no-contest plea and strike a new agreement or face a second trial, which Campbell called a “unique” feature of the deal. 

“(That’s) different than some plea agreements,” said Campbell.

Mills, who appeared at the hearing by video link while sitting in a sunny dining room next to defense attorney Rob Oldham, listened quietly to Campbell and sipped from a portable coffee mug. 

Mills is out of both prison and jail now on bond. 

Three Years, No Freedom

Mills has spent the last three years in jail and prison. He was arrested hours after Bartlett’s death in March 2020 and remained in jail throughout his prosecution.

A trial jury convicted him of second-degree murder a year after Bartlett’s death. The court later sentenced Mills to between 20 and 25 years in prison. 

The Wyoming Supreme Court in December overturned Mills’ conviction because his arresting officer, Riverton Police Department Detective Jim Donahue, did not read Mills his Miranda rights, even while asking Mills what the high court called “accusatory” questions. 

Campbell told Mills on Thursday that he probably didn’t need to remind Mills of the possible consequences to which his no-contest plea would lead, but he would anyway. 

“In your particular circumstance, you’ve suffered all the consequences already, including prison time, because of the special nature – the nature of how you got here,” said Campbell. 

Still, Campbell discussed with Mills the ramifications of accepting a conviction for a violent felony, which include the loss of gun, voting, jury and public-office rights. 

New Report, Sort Of

Campbell ordered Mills to report to probation and parole office researchers, who will update his pre-sentence investigation report from 2021.

A pre-sentence investigation report is a synopsis of a defendant’s life and issues designed to acquaint the judge with that person before a judge sentences him or her. 

Campbell said Mills needs only to update his original report to account for the last two years of his life. 

“I’m guessing it’s a very brief update,” said Campbell, “because, unfortunately, he was in custody.” 

Once the report is finished, Campbell can sentence Mills.

“(The prosecution is) not quite over, for the victims, the state or of course principally for Mr.Mills,” Campbell said. “We are on our way; we will see each other again at the sentencing proceeding.” 

In The Garage

According to court documents and testimony, Mills shot Bartlett in the head while the pair were drinking and playing cribbage, then arguing, in Mills’ garage in March 2020. Mills’ wife originally reported the death as a suicide, but the wound and other patterns at the scene indicated the gun was farther from Bartlett’s head than a self-inflicted wound would allow.

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Clair McFarland

Crime and Courts Reporter