A 16-year-old student charged with stabbing 20 fellow students and a security guard at his suburban Pittsburgh high school waived his right to a preliminary hearing Monday.

By waiving the hearing, which had been scheduled for Wednesday, Alex Hribal and his attorney acknowledge prosecutors have enough evidence for Hribal to stand trial.

Defense attorney Patrick Thomassey didn't immediately return messages for comment on the filing. But Thomassey has said he plans to ask a judge to move the case to juvenile court, where Hribal would face incarceration or probation only until he's 21.

If the case remains in adult court, the former Franklin Regional High School sophomore faces decades in prison if he's convicted.

All the victims have been released from hospitals since the April 9 stabbings, the last one on May 17.

Hribal remains in a juvenile detention center and now that the case has moved to Common Pleas Court, Thomassey can ask a judge to move the case to juvenile court. Online court records show that has yet to occur.

Thomassey must convince a judge that Hribal's prospects of rehabilitation are greater if the case is moved to juvenile court, where there is more emphasis on treating offenders and less on punishment. Thomassey has he would raise the matter of the boy's mental state before a judge determining whether the case moves to juvenile court. If the case isn't moved, Thomassey has said Hribal's mental state should still be considered as part of his criminal defense.

Thomassey has acknowledged Hribal took two eight-inch kitchen knives from his home and began stabbing students who had arrived at the school in Murrysville, about 15 miles east of Pittsburgh, but had yet to begin their first class of the day.

Hribal faces 21 counts each of aggravated assault and attempted homicide, because police and county prosecutors said Hribal told those who disarmed him that day -- and related in a note found in his locker -- that he intended to kill his victims. Hribal also faces a charge of bringing illegal weapons to school.

Thomassey has suggested that Hribal may have bullied before the attacks, but has not commented on specific evidence or incidents to support that. Murrysville police Chief Thomas Seefeld has said investigators haven't uncovered any evidence of bullying, but he could not be reached for updated comment Monday.

Westmoreland County District Attorney John Peck declined comment on Hribal's decision to waive the hearing.

Hribal next faces formal arraignment July 23 in Common Pleas Court.