( CNN ) -- James Holmes was in `` the throes of a psychotic episode when he committed acts that resulted in the tragic loss of life '' at a Colorado movie theater a year ago , his attorneys said in a court filing . It is the first time the defense has admitted that Holmes killed 12 people in the mass shooting , The Denver Post reported . The judge in Holmes ' murder trial last month accepted the defendant 's plea of not guilty by reason of insanity . Suspect to wear hidden harness during trial . Holmes previously offered to plead guilty and spend the rest of his life behind bars if authorities would spare his life , but prosecutors in Arapahoe County announced in April they would seek the death penalty . The defense then decided to make an insanity plea . Judge Carlos Samour Jr. has told attorneys he expects the trial to take place in 2014 . The burden is on the prosecution to prove that Holmes was sane at the time of the shootings . Attorneys will use the results of a mental evaluation as evidence at the trial . Holmes faces murder and other charges in the July 20 , 2012 , shooting spree at the premiere of the Batman movie `` The Dark Knight Rises . '' Rescue workers were n't prepared for chaos of Aurora shooting . CNN 's Jim Spellman and Shawn Nottingham contributed to this report .
In a court filing , Holmes admits to the mass shooting for the first time . He is the suspect in last year 's shooting spree at a movie theater in Colorado . Court document says he was having `` a psychotic episode '' at the time of the shooting .