Police say Holmes, now 25, had stockpiled weapons, ammunition, explosives and body armor. He was a first-year student in a Ph.D. neuroscience program at the University of Colorado, Denver, but he failed a year-end exam and withdrew in June, authorities have said.
The shootings happened six weeks later.
Federal authorities have said Holmes entered the theater with a ticket and is believed to have propped open a door, slipped out to his car and returned with his weapons. Police arrested him outside the theater shortly after the shootings ended.
Holmes' mental health could be a significant issue — and possibly a contentious one — in the preliminary hearing.
His attorneys have told the judge Holmes is mentally ill, but they have not said whether they plan to employ an insanity defense. He had seen a university psychiatrist, and his lawyers have said he tried to call the psychiatrist nine minutes before the killing began.
Defense lawyers have said they plan to call at least two witnesses who could testify about Holmes' mental health. Prosecutors asked Sylvester to block the witnesses, but he refused.