Austin Sigg, the teen accused of murdering 10-year-old Jessica Ridgeway, pleaded not guilty to all charges, including murder and kidnapping, during his arraignment on Friday.

A trial is set to begin on Sept. 20 with jury selection.

Sigg is facing 18 charges, including first-degree murder, kidnapping, sexual assault and sexual exploitation of a child.

During the preliminary hearing on Feb. 22, Westminster investigator Louis Lopez testified that Sigg confessed to the murder of Ridgeway during a 911 call.

According to a tape played at the preliminary hearing, Sigg told the dispatcher “I murdered Jessica Ridgeway, I have proof.”

He said the remains were in the crawl space at his home, and he was giving himself up completely. Police investigated Sigg’s home in Westminster and found the remains.

Lopez testified that Ridgeway’s death was asphyxiation, according to the coroner.

Sigg is accused of kidnapping and killing Ridgeway in early October 2012 while she was walking to school. He is also accused of attempting to abduct a woman jogging around Ketner Lake in May 2012.

Detective Michael Lynch also testified during the preliminary hearing about an interview he had with Mindy Sigg, Austin’s mother.

According to Lynch, Sigg told his mother that he did not rape Jessica. Lynch testified that Sigg told his mother that he grabbed Jessica as she walked by his car, put her in his back seat.

Sigg told his mother he was a monster and that he was also responsible for the attempted abduction of the jogger as well, according to Lynch.

Friday’s hearing was a continuation of a March arraignment, which at that time Sigg’s defense team asked for additional time to investigate possible defenses.

Defense attorney Katherine Spengler told the judge the team needed the extra time to thoroughly go through every piece of discovery, which included 50,000 pages of information, 2,500 photos and 1,800 pieces of physical evidence.

Originally, the defense team asked for an additional two months due to the massive amount of information in discovery, but Judge Stephen Munsinger offered only a 30-day extension.