James Holmes’ attorneys revealed his intention Tuesday. The new plea could mean a long delay for a mental evaluation and legal arguments.
Holmes is charged with multiple counts of murder and attempted murder in the July 20 attack that killed 12 people and left 70 injured. Prosecutors are seeking the death penalty.
Holmes’ lawyers delayed entering a plea for weeks, saying the state insanity law could severely hamper his ability to mount a defense against the death penalty.
A judge entered a standard not guilty plea for Holmes last month.
The court will hear arguments from both sides Monday on whether to let Holmes change his plea to insanity.