Davis County prosecutors have said they will seek to certify the teen and prosecute him in adult court.
But before an adult-certification hearing occurs, Judge Janice Frost will hear evidence surrounding the alleged May 22 slayings at a preliminary hearing set for Aug. 27.
Utzinger said he and the teen's family hope to keep the case in juvenile court.
"He just barely turned 15," the attorney said, adding that he believes the adult prison system could "cause serious harm to [the boy's] psyche."
During Tuesday's hearing, the boy handcuffed and wearing a blue jumpsuit displayed no apparent emotion as he gave brief answers like, "Yes," and "Yes, Ma'am," and "No questions," to the Frost's questions, including whether the boy understood the charges against him and what would happen next.
Davis County Sheriff Todd Richardson has said that the bodies of the two victims were found in their West Point home on May 22 around 7:35 p.m. He said the boys appeared to have suffered "penetrating knife wounds."
Deputies rushed to the home at 120 S. 1660 West after the boys' mother called 911 to report finding her 4-year-old son dead on the floor of the home, and her 15-year-old and 10-year-old sons missing.
Deputies found the 10-year-old's body in another part of the house, then issued a missing person alert for the 15-year-old, who was found late that night in nearby Layton.
The Salt Lake Tribune initially reported the name of 15-year-old in an effort to help police locate him. However, after the teen's arrest, and consistent with the newspaper's policy of not naming juvenile criminal suspects, his name is now being withheld.
The teen was found walking on the street by Layton police about 11:30 p.m., some eight miles from the crime scene. Authorities said the teen did not have a weapon when he was found, but traces of blood were found on him. He was taken to the hospital to be checked before questioning and was then booked into the Farmington Bay Youth Detention Center on suspicion of two counts of homicide, Richardson said.
The teen has no criminal history, according to court officials.