The suspect in the Colorado cinema massacre, in which 12 moviegoers were killed and another 58 injured, was seeing a psychiatrist, according to court documents made public.
A motion filed in a Colorado court named Dr Lynne Fenton, a psychiatrist at the University of Colorado. Defense attorneys are working to gain access to a package that suspect James Holmes reportedly sent to Dr Fenton prior to the attack.
The package was seized by police earlier this week.
Media reports earlier this week quoted law enforcement officials as saying the package contained a journal detailing plans of the attack.
The filing came just three days before Holmes was due in court to face charges. Holmes' previous court appearance last Monday sparked widespread speculation about his mental health given his strange demeanor.
The defense lawyers also argued that the contents of the package should not be used as evidence because such communications were "protected." The filing named Holmes as a patient of Fenton’s.
Television cameras will not be allowed in the courtroom for Monday's hearing.
Prosecutors rebuffed the defense motion, arguing that news stories about the package contained significant "factual errors" and that there was no evidence the government was responsible for the leaks.
Holmes, who was studying neuroscience in a doctoral program at the University of Colorado, Denver, is expected to be formally charged on Monday. The judge also ordered a hearing on the defense motions be held that day.
Holmes allegedly gained access to the movie theater in Aurora, Colorado, via a fire exit shortly after the screening of The Dark Knight Rises began and threw two canisters of noxious gas into the auditorium.
Witnesses said that he began shooting people at random with a military-style assault rifle after firing one round into the air.
Authorities say Holmes - who had dyed his hair a reddish orange - claimed he was the Joker, Batman's sworn enemy in the comic book series that inspired director Christopher Nolan's film trilogy.
Holmes, 24, is being held in solitary confinement at the Arapahoe County Detention Center and could face the death penalty if convicted.
tm/tj (AFP, dpa)