Key issues as Colorado theater shooting trial begins

FILE - In this July 27, 2012 file photo, crosses, flowers and other mementos of the victims of the Aurora, Colo. movie theater shooting are shown at sunrise with the movie theater in the background. Jury selection begins Tuesday, Jan. 20, 2015, in the trial of accused gunman James Holmes in the shootings at the Denver-area movie theater showing "The Dark Knight Rises" that left 12 dead and 70 wounded. Prosecutors are seeking the death penalty. Holmes pleaded not guilty by reason of insanity. His attorneys have acknowledged he was the gunman but say he is mentally ill and was gripped by a psychotic episode when he opened fire in the theater. (AP Photo/Ted S. Warren, File) (The Associated Press)

FILE - In this July 23, 2012 file photo, James Holmes, who is charged with killing 12 moviegoers and wounding 70 more in a shooting spree in a crowded theatre in Aurora, Colo., in July 2012, sits in Arapahoe County District Court in Centennial, Colo. Holmes' trial is set to start on Tuesday, Jan. 20, 2015. (AP Photo/Denver Post, RJ Sangosti, Pool, File) (The Associated Press)

Jury selection in the trial of the man accused of killing 12 people and injuring 70 others in an attack on a Colorado movie theater is set to begin, with the first of 9,000 prospective jurors reporting to court on Tuesday.

Their task will be to decide whether James Holmes was legally insane at the time of the July 20, 2012, attack during a showing of a Batman movie in the Denver suburb of Aurora.

Holmes, now 27, is charged with multiple counts of first-degree murder and attempted murder, and has pleaded not guilty by reason of insanity. If jurors agree, he would be committed indefinitely to the state psychiatric hospital.

Prosecutors dispute that Holmes was insane. They will ask jurors to convict him of murder and sentence him to die, though Colorado has executed only one person in the past 40 years.

Here is a look at the key issues in the case:

THE CRIME: About 420 people were watching a midnight showing of "The Dark Knight Rises" when a masked figure standing near the screen tossed gas canisters into the audience and opened fire. Witnesses described a scene of hellish chaos as victims fled or dived for cover. Holmes surrendered to police outside the theater.

THE VICTIMS: The dead included a 6-year-old girl, two active-duty servicemen, a single mom, an aspiring broadcaster who survived a mall shooting in Toronto and a 27-year-old celebrating his birthday and wedding anniversary. Several of the victims died shielding their friends and loved ones.

THE DEFENDANT: Holmes had just dropped out of a Ph.D. program in neuroscience at the University of Colorado, Denver, after flunking a key test. Prosecutors suggested he was angry his once-promising academic career ended in failure. Defense attorneys acknowledged Holmes was the shooter but said he was mentally ill and in the grips of a psychotic episode. Holmes first appeared in court with a dazed look and jarring orange hair. In more recent months he has appeared nonchalant, sometimes with a bushy beard and hair, other times clean-shaven with hair combed back.

WHY THE TRIAL IS SO LATE: The death penalty and the insanity plea introduced multiple, complicated and time-consuming legal requirements. Holmes has undergone two court-ordered sanity evaluations, and the two sides have amassed 85,000 pages, 366 CDs and 282 DVDs of evidence.

THE CRUX OF THE TRIAL: The key question before jurors will be whether Holmes was legally insane — unable to tell right from wrong because of a mental disease or defect. If Holmes is found guilty of murder, the jury would then decide whether he should be sentenced to life in prison without the possibility of parole or executed. If he is found not guilty by reason of insanity, he would be committed indefinitely to the state mental hospital. A straight not-guilty verdict is considered unlikely because his lawyers have acknowledged he was the gunman, and the evidence that he pulled the trigger is overwhelming.

HOW THE JURY WILL BE CHOSEN: Judge Carlos A. Samour Jr. called an unusually large number of people for jury duty, citing the difficulty in finding an unbiased panel. Samour expects it to take until May or June before he can find 12 jurors and 12 alternates. Prosecutors will try to ensure jurors have no reservations about the death penalty while defense attorneys will look for those sympathetic to mental illness and uneasy with the idea of executing a person.

WHAT JURY LIFE WILL BE LIKE: Jurors won't be sequestered — isolated in a hotel — but will be allowed to go home every night. Samour will tell them they may not discuss the case with anyone, do any independent research on it, or watch, read or listen to news reports about it. Their names won't be made public, and Samour has forbidden news organizations from taking their photos.