Quintanilla has been locked up at the Salt Lake County jail since his arrest in lieu of a $2 million bail.
According to charging documents, Unified police officers found Steffy at her home at 3972 W. Blue Meadow Drive inside a crawl space with two black trash bags wrapped around her body.
An autopsy concluded that Steffey died "from a combination of factors, including blunt force trauma, suffocation and strangulation," court documents state.
Detectives tied the killing to Quintanilla when they began to look into transactions from Steffey's stolen ATM card, which had been used to withdraw more than $1,500 in the course of three days before and after the woman was found dead.
Surveillance video from the ATMs depicted a man wearing a light-colored hoodie and black pants, driving a Nissan Versa.
Quintanilla was arrested on April 19, when a detective watching a Chase Bank at 3029 S. Colt Plaza in West Valley City saw a man who matched the suspect description approach the ATM.
Police found Steffey's ATM card in the man's front pocket and a plane ticket for El Salvador in his car, according to the charges. His flight was scheduled to leave Salt Lake City International Airport in three hours.
Quintanilla later admitted to the police that he used Steffey's card eight times, court documents reveal. But he denied ever being in Steffey's home.
But state crime lab investigators found a fingerprint on one of the black trash bags that matched a print taken from Quintanilla at the time of his arrest.
Quintanilla and Steffey were acquaintances, Salt Lake County Sheriff Jim Winder said, though he declined to elaborate on how they knew each other.