Colorado theater shooter James Holmes was convicted Thursday of killing 12 people and injuring 70 in a methodical attack on a midnight movie premier in July 2012. Here's a look at the key elements in the case:

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THE CRIME:

About 420 people were watching a midnight showing of "The Dark Knight Rises" on July 20, 2012, in the Denver suburb of Aurora when Holmes opened fire, killing 12 people.

Fifty-eight others were wounded by gunfire, and 12 were injured in the scramble to escape. Holmes surrendered to police outside the theater.

His attorneys acknowledged he was the gunman, but they said he was in the grip of a psychotic episode.

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WHAT'S NEXT?

Under Colorado law, the jurors now will hear testimony and then decide on the penalty — death or life in prison without parole — in the sentencing phase of the trial. Both sides can present witnesses before the jury decides.

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THE TRIAL:

The trial began with opening statements April 27. Over the next 11 weeks, jurors heard from more than 250 witnesses, viewed more than 24 hours of video and saw more than 1,500 photos, some of them disturbing images of the victims. They also examined scores of pieces of evidence, including Holmes' guns and ammunition. Holmes didn't testify. The jury began deliberating July 15.

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THE MOTIVE:

Prosecutors said Holmes planned and carried out the massacre to assuage the pain of his failures in graduate school and in romance. Defense lawyers said schizophrenia had been growing inside Holmes' mind for years and eventually overwhelmed him in 2012, creating a delusion that he could improve his self-worth by killing others and absorbing their value.

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SANE OR INSANE?

Holmes pleaded not guilty by reason of insanity, which under Colorado law means he acknowledged committing the acts but believed he wasn't responsible because he couldn't tell right from wrong. Two court-appointed psychiatrists testified he was legally sane; two defense psychiatrists told jurors he was legally insane.

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THE JURY:

The judge originally seated 12 jurors, plus 12 alternates to replace any jurors who had to be dismissed for health or other reasons. Five were dismissed during the trial, either for seeing news reports about the case or, in the case of one juror, because a family member was injured in an unrelated crime. The 12 deliberating jurors and the seven remaining alternates were identified after closing arguments July 14.

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WHY HAS IT TAKEN SO LONG?

It took 2½ years for the judge, prosecution and defense to plow through the mountain of evidence and hash out numerous legal questions. Further complicating matters were the number of victims, the prosecution's decision to seek the death penalty and Holmes' decision to plead not guilty by reason of insanity. It took nearly three more months to choose the jury after 9,000 summonses were sent.

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WHY WAS THERE NO PLEA AGREEMENT?

Holmes offered to plead guilty if prosecutors would agree to a life sentence without parole. Prosecutors rejected the offer.