Crutcher, 32, was charged Monday with first-degree felony aggravated murder. He is scheduled to make his initial appearance in 6th District Court on Nov. 13.
Sanpete County Attorney Brody Keisel said Friday that Cardona-Gueton was found on April 20 "as if he had [hanged] himself."
"Further investigation has led us to conclude that this is not a suicide, but an aggravated homicide," Keisel said.
Keisel would not discuss what evidence led investigators to become suspicious about the death but said a bedsheet that was torn into strips and braided together was used to kill Cardona-Gueton, who had been at the prison since 2011, serving time for theft and drug distribution.
Keisel said the case qualifies as aggravated murder because it happened inside a prison.
The Utah Department of Corrections released a statement about the death on April 20, describing it as "suspicious."
While the department does not notify the public when inmates die of natural causes, in this case it opted to be proactive and "provided more information than less" because of the circumstances, said spokesman Steve Gehrke.
Cardona-Gueton's name was initially withheld while the department tried unsuccessfully to locate family members. Three days after Cardona-Gueton was found dead in his cell, the department released his name and said an investigation by the Gunnison Police Department was ongoing to determine "whether any foul play was involved."
Crutcher is serving a sentence of up to life in prison for an aggravated kidnapping charge in June 2009, according to court records. According to the Associated Press, Crutcher attempted to escape the Iron County jail when he cornered a deputy at the jail and threatened to detonate a bomb if he wasn't released. It was later discovered that the "bomb" was fashioned from toilet paper rolls, headphone wires and a pencil eraser.
Crutcher was at the Iron County jail in 2009 on suspicion of stealing a car. He eventually pleaded guilty that year to second-degree felony theft by receiving stolen property in Cedar City and was sentenced to another one to 15 years at the prison.
Keisel said Friday that Crutcher and Cardona-Gueton had been in a cell together for just a few days before the alleged murder. He would not publicly discuss a motive for the killing, but said they are investigating whether race played a part.
Because of the criminal investigation, Gehrke declined to comment on whether Crutcher had any disciplinary record at the prison, though he did say the inmate was not listed as a member of any gangs.