According to the stipulation, filed in court Thursday, the teen twice refused to waive his Miranda rights. However, investigators continued to ask him questions about the double-slaying at his home on May 22. He finally gave a number of statements regarding his brothers' deaths.
Outside of court, defense attorney Todd Utzinger called the violation of the teen's rights "egregious," saying that on the morning of May 23, four detectives from the Davis County Sheriff's Office put the teen into an interrogation room and continued to pressure him to give statements even after he refused several times and had fallen asleep twice.
"It's puzzling to me how that could have happened with four detectives present," he said.
Prosecutors declined to answer questions after the hearing about how the loss of the boy's statements to police might affect the case.
But certain other spontaneous statements made by the teen can still be used by prosecutors, according to attorneys and court documents. Also, police have previously said that traces of blood found on the teen link him to the crime scene.
Prosecutors have previously said they will seek to certify the teen and prosecute him in adult court; however, a certification hearing won't be held until after the preliminary hearing.
The teen will appear in court on Feb. 27 for a status hearing.
Davis County Sheriff Todd Richardson would not discuss the teen's case specifically with members of the media on Thursday but said the detectives in his office do receive "extensive training" on how to conduct interrogations and interviews.
Richardson previously 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 teen was found walking on the street by Layton police about 11:30 p.m., about eight miles from the crime scene.
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.