James Holmes, Aurora theater shooting suspect, sits in the courtroom during his arraignment in Centennial, Colo., on Tuesday, March 12, 2013.
A judge on Tuesday accepted James Holmes' plea of not guilty by reason of insanity, setting the stage for a lengthy mental evaluation of the Colorado theater shooting suspect the Associated Press reported.
The evaluation of the Rancho Penasquitos resident could take weeks or even month.
Holmes faces 166 counts of murder, attempted murder and other offenses in connection with the July 20 shooting in an Aurora, Colorado movie theater that left 12 dead and 58 wounded.
Prosecutors are seeking the death penalty. They say Holmes, a former neuroscience graduate student, spent months acquiring weapons and ammunition, scouting a theater in the Denver suburb of Aurora and booby-trapping his apartment.
Then on July 20, dressed in a police-style helmet and body armor, he opened fire during a packed midnight showing of "The Dark Knight Rises," prosecutors say.
Holmes, a Westview High School graduate, attended UC Riverside where he graduated a BS in neuroscience in 2010. He then went to Colorado where he was pursuing his graduate degree.
While in San Diego, James Holmes lived with his parents Robert and Arlene Holmes on Sparren Avenue in Rancho Penasquitos.
Arlene Holmes, a registered nurse, works with Tri-City in Oceanside. The defendant's father, Robert Holmes, is a software engineer who lists his employer as a Carmel Valley company.
No motive has emerged in nearly 10 months of hearings, but Holmes' attorneys have repeatedly said their client is mentally ill. He was being treated by a psychiatrist before the attack.
A not guilty by reason of insanity plea is widely seen as Holmes' best hope -- perhaps his only hope -- of avoiding the death penalty.