(CNN) -- The trial of James Holmes, accused in the mass shooting at an Aurora, Colorado, movie theater, has been delayed again.
The trial was scheduled to begin in October, but a psychiatrist conducting a second sanity examination on Holmes asked for more time to complete the examination, according to a judge's order from Arapahoe County District Court made public Wednesday.
Judge Carlos Samour said he had "little choice but to grant the examiner's request" despite the fact many victims would be opposed to the delay.
The examination was originally set to be completed by August 15, but the deadline was extended until October 15, according to the order. A new trial date is set to be scheduled at a July 22 hearing.
Holmes is accused of opening fire inside a packed movie theater during a midnight showing of Batman film "The Dark Knight Rises" in July 2012, killing 12 people.
He has pleaded not guilty by reason of insanity to the 166 charges he faces in connection with the rampage.
The attacker threw tear gas canisters into the theater then started shooting, according to witnesses. Police said he used several weapons, including an AR-15 rifle, before fleeing the theater.
Holmes was taken into custody outside the theater, where authorities said he identified himself to police as "The Joker," one of Batman's archenemies.
This is the third time the trial has been delayed. It was originally set to begin in August 2013 but was pushed back to February. That date was then delayed until October, which has now been postponed.
Holmes' attorneys argued in a motion filed last year that their client "suffers from severe mental illness and was in the throes of a psychotic episode when he committed acts that resulted in the tragic loss of life."
Prosecutors have said they plan to seek the death penalty.