District Judge Stephen Munsinger also ordered the 17-year-old's transfer from a juvenile facility to a special holding area in an adult jail, The Denver Post reported. He would be separated from adult prisoners and would have greater access to education and recreation than he does now.
Sigg is being held without bail on charges that include felony murder and kidnapping.
He has also been charged with the attempted murder, kidnapping and sexual assault of a jogger in late May, more than four months before Jessica disappeared.
At Tuesday's hearing, Sigg's lawyers waived a challenge to an adult trial. They did object to his transfer to an adult jail, arguing he has not been a "management problem" at the Mount View Youth Services Center.
Dave Maynard, the manager of the center, said he is concerned about the safety of the other children, some as young as 10, being held there. He said he is also worried because some of the inmates have made threats against Sigg.