An insanity plea would complicate the prosecutors' decision of whether to seek the death penalty against James Eagan Holmes, 25, who entered the Aurora theater shortly after the start of a midnight showing of "The Dark Knight Rises" on July 20, 2012 and sprayed the crowd with gunfire.
Holmes reportedly made several attempts at suicide in November, while in jail awaiting his arraignment.
According to Colorado Bar Association, for an insanity defense "a person [must be] is so diseased or defective in mind at the time of the commission of the act as to be incapable of distinguishing right from wrong with respect to that act is not accountable."
Holmes, should he make an insanity plea, would waive medical confidentiality and turn over the name of his treating physicians, medical records, and submit to testing by doctors so the state can assess his mental state.
Holmes's defense attorneys attempted to strike parts of the state's insanity defense laws as unconstitutional, claiming the required psychiatric evaluation violated the right to avoid self incrimination. Those claims were dismissed by a judge last week.
Family members of some of the victims told CNN an insanity plea would allow Holmes to get away with crimes for which he allegedly spent months building an arsenal and scoping the theater.
He is "absolutely not" insane, said Jessica Watts, whose cousin was among those killed in the theater. "This was months and months of planning and thousands of dollars spent on his part in order to pull this horrific night off."