Dimarzio Swade Sanchez

Dimarzio Swade Sanchez

A man convicted of murdering a woman on the Crow Reservation in 2016 by strangling her and lighting her on fire has been denied a new trial, despite arguments by defense attorneys that federal prosecutors withheld evidence that could have helped his case.

Judge Susan Watters issued her order denying Sanchez's motion for a new trial Monday in U.S. District Court in Billings.

Dimarzio Swade Sanchez faces a possible lifetime prison term after he was convicted of the first degree murder of 28-year-old Roylynn Rides Horse. She died in June 2016, two months after she was strangled, doused with gasoline, lit on fire and left in a field. She was found 14 hours later by a passerby.

Sanchez was the last of three defendants to be convicted in connection with Rideshorse's slaying. He was found guilty at the conclusion of a four-day jury trial in December.

The defense's only witness in the trial was a psychologist who testified that Sanchez's mental disability made it impossible for him to have "formed the requisite intent to commit first-degree murder."

After he was convicted, Sanchez's lawyers moved for a new trial, alleging that the government failed to disclose that the psychologist was under a state indictment at the time for obtaining possession of a controlled substance by theft, misrepresentation, forgery or fraud.

In court filings, defense attorneys suggested that the psychologist could have been under the influence of drugs when she examined Sanchez and when she testified on his behalf.

"The probability exists that even though the jury found Mr. Sanchez guilty of first degree murder, an acquittal would probably have resulted if a different or unimpaired expert testified," public defender Gillian Gosch wrote.

However, Watters found the defense failed to establish that the additional information about Sanchez's witness would have changed the outcome of the trial.

Sanchez's attorneys also argued that the government withheld potentially exculpatory evidence found on a cell phone after his trial, which appeared to contradict testimony provided by the prosecution's witnesses.

Watters rejected that argument, writing that the note saved in the phone "does not conflict with the four eye witness accounts, and the jury's determination, of Dimarzio's role in (Rides Horse's) murder." She also ruled that the government had disclosed the new evidence in a timely fashion.

Sanchez is scheduled to be sentenced Dec. 21.

Sanchez's brother, Frank, pleaded guilty to being an accessory after the fact last year, and Angelica Jo Whiteman pleaded guilty to aiding and abetting first-degree murder. Both co-defendants are also scheduled to be sentenced in December.

Photos: March for Roylynn Rides Horse in 2016

Sign up for our Crime & Courts newsletter

* I understand and agree that registration on or use of this site constitutes agreement to its user agreement and privacy policy.