Holmes said only one word during Monday's hearing. "Yes," he answered when asked by the judge if he agreed to waive his right to a preliminary hearing in the next 35 days.
The district attorney near Denver has not announced if she will seek the death penalty against the alleged gunman.
A dozen people were killed and 58 were wounded after a gunman burst into a sold-out midnight viewing of the latest Batman film, "The Dark Knight Rises," and began shooting people at random.
Under Colorado law, defendants are not legally liable for their acts if their minds are so "diseased" that they cannot distinguish between right and wrong. However, the law warns that "care should be taken not to confuse such mental disease or defect with moral obliquity, mental depravity, or passion growing out of anger, revenge, hatred, or other motives, and kindred evil conditions."
Court documents filed on Friday by defense lawyers said the suspect had been under the care of a psychiatrist at the University of Colorado Denver, where he had been in the process of dropping out as a neuroscience PhD student.
Alleged Colorado cinema gunman James Holmes has been formally charged with two dozen counts of first-degree murder.
Prosecutors on Monday also charged Holmes, 24, with slew of other violent offenses related to the recent deadly rampage at a Colorado movie theater, the Associated Press reported.