Black is being held at the Salt Lake County jail in lieu of $2 million bail.
Black who lives near the canal and reportedly attends the same LDS church as the victim's family became a suspect after being arrested June 29 for an unrelated auto theft and a Wells Fargo bank robbery.
Gill said the girl was abducted from her home, then beaten, raped, strangled and thrown into the canal, where she drowned, according to an autopsy.
Assistant Utah Medical Examiner Julie Adams, who performed the autopsy, found contusions on the side of Sierra's face, under each eye and on several areas on her back, according to the charges. Also, Adams and Dr. Karen Hansen, with Primary Children's Medical Center, saw evidence of sexual assault.
Police found Sierra's body at 8:22 a.m. on June 26 in a canal about a block from her home.
The discovery occurred about an hour and 10 minutes after her mother reported the girl missing from the family's home near 2400 W. 7100 South.
The girl's mother called police after finding a sliding door open and Sierra missing from her bed at about 7:10 a.m. She told police she had last seen her daughter at about 10:30 p.m. the night before.
Police later viewed home security camera footage which showed a "form" entering the home at 3:05 a.m, and exiting "carrying something" at 3:13 a.m., according to charges.
Police later found clothing items belonging to the girl pink pajama bottoms and her underwear in a field near the canal that had been blackened by the recent fire.
An officer found the girl's partially clad body in the canal, which borders the field, and her clothing was darkened with debris consistent with the burned material from the field.
After Black's arrest, a swab from Black's genitals was obtained and compared to DNA from Sierra's body. Examiners at the Utah State Crime Laboratory subsequently found Sierra's DNA profile on the swab taken from Black, according to charges.
The three charges filed against Black on Monday are all first-degree felonies. Prosecutors could opt to pursue the death penalty in connection with the murder count.
The robbery that led to Black's arrest occurred June 29 when, according to police, Black entered the Wells Fargo Bank, 7869 S. Redwood Road in Salt Lake County, and told the teller that he needed $100.
According to a probable cause affidavit, when the teller asked Black for identification, he told the woman, "This is a robbery."
The teller took a $100 bill from her drawer and gave it Black. She then asked if he wanted $400, and he told the teller he wanted $4,000, according to court documents.
When the teller told Black that she would have to go to the vault for that, Black left the bank.
After Black left the bank, a service manager at the bank was able to snap a photo with her cell phone as he was trying to get into a Jeep.
Earlier that morning, an employee at the Deseret Industries, located at 7166 S. Redwood Road, reported that her Jeep had been stolen from the parking lot.
Her boss later went to the Wells Fargo Bank to deposit a check, and spotted the stolen Jeep in the bank's parking lot. When she saw Black attempt to get into the vehicle, the woman confronted him and told him to get away from the car, according to court records. She also took a photo of Black with his cell phone.
Black fled the area on foot, but was arrested nearby. He was charged on June 30 with robbery and receiving or transferring of a stolen vehicle, both second degree felonies.
Black's criminal history includes a 2008 guilty plea to burglary of a vehicle, a class A misdemeanor. An additional charge of burglary of a vehicle, two counts of criminal mischief and one count of intoxication where dismissed as part of a plea deal.
Tribune reporter Jessica Miller contributed to this story.