"The evidence is overwhelming," Chief Deputy District Attorney Hal Sargent said at Sigg's initial court appearance on Thursday in Golden, Colo. Sigg, 17, was ordered to return to court Tuesday, when he is expected to be charged as an adult. He is not eligible for the death penalty because of his age.
Members of Ridgeway's family attended the hearing dressed in purple, her favorite color. Sigg's family also attended, and wept as he entered.
At one point, Sigg turned to look back at his mother, Mindy Sigg, who says she called police, reportedly after speaking with her son.
Prosecutors declined to comment further in court or outside the courtroom.
Sigg, shackled and handcuffed and under watch by 14 officers, appeared calm and alert. But as the judge explained to him what was going on in court Thursday morning, Sigg said, "I don't understand."