( CNN ) -- The judge in James Holmes ' murder trial on Tuesday accepted his plea of not guilty by reason of insanity . The suspect in last summer 's shooting spree that killed 12 people and wounded dozens at an Aurora , Colorado , movie theater will be taken to the Colorado Mental Health Institute at Pueblo for evaluation . He 's expected to be returned to the Arapahoe County Jail on August 2 . 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 the mental evaluation as evidence at the trial . Samour 's ruling Tuesday came about a month after Holmes ' attorneys asked to change his plea from a standard not guilty . The original not-guilty plea was entered by a judge on Holmes ' behalf in March , over his objection , his defense team said . The defendant 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 . Asked by the judge Tuesday whether he had any questions about the plea , Holmes replied in a clear voice , `` No . '' Samour also ruled Tuesday that a package Holmes mailed to his psychiatrist before the shooting can be processed as evidence . He sent Dr. Lynne Fenton $ 400 in burned $ 20 bills , a sticky note with an infinity sign , and a spiral notebook containing a placard . Written on it : `` James Holmes , Of Life , '' according to court documents . The defense had previously argued that the contents of the package is covered by doctor-patient confidentiality . But with an insanity plea , that confidentiality no longer applies . Before the shooting , Fenton , who works at the University of Colorado 's medical campus , warned campus police that Holmes was dangerous . Holmes faces murder and other charges in the July 20 shooting spree at the premiere of the Batman movie `` The Dark Knight Rises . ''
A package James Holmes sent to his psychiatrist will be processed as evidence . Holmes will be taken to a mental health center for evaluation . He faces murder and other charges in a 2014 shooting at an Colorado , Aurora , movie theater . Trial is set for 2014 .