CENTENNIAL, Colorado (REUTERS) - The first of some 9,000 potential jurors will report to court in Colorado on Tuesday as selection begins for the trial of James Holmes, the former neuroscience graduate student who killed 12 people in July 2012 at a midnight screening of a Batman movie.
Holmes, 27, has pleaded not guilty by reason of insanity to 166 charges of murder, attempted murder and explosives offences. He was arrested wearing a gas mask, helmet and body armour at the scene of the shooting rampage in the Denver suburb of Aurora. Seventy people were also hurt.
His lawyers have said Holmes was suffering a "psychotic episode" at the time. If convicted, he could face the death penalty.
Jury selection may take up to four months as Arapahoe County District Court Judge Carlos Samour seeks to narrow the large field to a panel of 12 jurors and 12 alternates.
So many people were summoned because of the difficulty expected in finding an impartial jury for such a high-profile, emotive case. Each will be questioned about their views on topics such as insanity defences and the death penalty.
Television news satellite trucks lined up before dawn outside the county courthouse, where a lone police car patrolled the icy parking lot.
Holmes, who first appeared in court in the days after the shooting looking dazed and with his hair dyed red-orange, is expected to be back in a courtroom on Tuesday afternoon when the first group of 250 potential jurors will be addressed by the judge, watch a video on jury duty and fill out questionnaires.
The trial has been delayed several times, mostly by wrangles over Holmes' state of mind when he opened fire with a handgun, shotgun, and semi-automatic rifle inside the crowded premiere of The Dark Knight Rises film at the Century 16 multiplex in Aurora.
The Southern California native has undergone two-court ordered sanity exams since his arrest. They have produced dozens of hours of video and thousands of documents, all sealed by the judge, but according to court papers they provided conflicting results.
At a preliminary hearing in January 2013, prosecutors gave a preview of the evidence that will be used against him at trial.
First responders testified to horrific scenes in the body-strewn theatre 9, where blood pooled on the floor and the movie still played, its soundtrack blaring. A fire alarm rang, strobe lights flashed, and wounded victims screamed.
One policeman said he initially mistook the gunman for a fellow officer because he was wearing body armour. But he soon realised it was not police issue gear and saw Holmes was acting oddly. Holmes was ordered to the ground and handcuffed.
Another officer testified that when Holmes was then asked whether he had an accomplice, he replied: "No, it's just me."
Holmes has spoken just twice in open court, uttering one-word responses when asked questions by the judge.
The honours undergraduate student at the University of California, Riverside, has no criminal record and was courted by the neuroscience doctoral programmes of several universities.
Holmes has been hospitalised at least twice since his arrest, according to his lawyers. Once he was treated for an apparent self-inflicted head injury, and on another occasion he was taken to a Denver psychiatric ward where his lawyers said he was held "frequently in restraints" for several days.
Holmes also faces charges for rigging his apartment near the theatre with explosives, which were defused by bomb technicians.