A Burt County district judge this week denied a request to move the 15-year-old boy's case to juvenile court.
Wilcox faces charges of first-degree murder, arson and forcible sexual assault.
Prosecutors say Wilcox sexually assaulted his 4-year-old half-sister, smothered her and then set a fire at the family's home on May 1.
He escaped from the flames with his mother and another sister.
Wilcox's attorney has said he has the mental capacity of a second-grader.
A hearing in the case is set for Feb. 3.
Viewers with disabilities can get assistance accessing this station's FCC Public Inspection File by contacting the station with the information listed below. Questions or concerns relating to the accessibility of the FCC's online public file system should be directed to the FCC at 888-225-5322, 888-835-5322 (TTY), or firstname.lastname@example.org.