James Holmes is accused of opening fire in a movie theater July 20, killing 12 people and wounding 70 others. He faces 166 counts of first-degree murder, attempted murder and weapons charges.
Holmes' lawyers said Monday their client "suffers from a serious mental illness," the Los Angeles Times reported.
Defense attorneys have argued unsuccessfully that entering an insanity plea and forcing Holmes to undergo state-ordered psychiatric evaluations jeopardized their client's constitutional rights. The defense said if Holmes were forced to cooperate during the evaluation, what he said could be used against him, violating his right against self-incrimination.
If he didn't cooperate, that lack of cooperation also could be used against Holmes at trial or sentencing and could bar the introduction of expert testimony about Holmes' mental state, the defense said.
Before he stepped aside, Chief District Judge William Sylvester dismissed the defense arguments, but left open the opportunity to revisit the issue because the prosecution hadn't yet announced it would seek the death penalty.
Prosecutor George Brauchler announced April 1 his office would seek the death penalty.
District Judge Carlos Samour Jr., who replaced Sylvester, issued several conditions that must be met before he is satisfied Holmes fully understands what an insanity plea means, the Times said.
In Monday's filing, the defense said Holmes "suffers from a serious mental illness," meaning it may be difficult to know whether he fully understands what's going on because his mental illness may prevent a "plausible grounding in reality."
Samour set a trial date for February. The next pretrial hearing is May 13.
Meanwhile, a federal judge ruled victim lawsuits against the theater's parent company could proceed, but in a narrower scope, the Times said.
U.S. District Judge R. Brooke Jackson ruled April 17 Cinemark USA could be potentially liable for damages under a Colorado law that states landowners are responsible for activities on their property. The judge also said Cinemark could not be found negligent by not better protecting patrons against the mass shooting.
So far, 10 victims sued the theater for unspecified damages.