CENTENNIAL, Colorado (REUTERS) - Colorado's long-awaited cinema massacre trial began on Monday with opening statements in which jurors were asked to decide whether gunman James Holmes was insane when he killed a dozen moviegoers in 2012, or a calculating mass murderer who deserves execution.
Public defenders trying to spare the life of the one-time neuroscience graduate student, and prosecutors seeking the death penalty, presented their opening statements in a packed courtroom on the outskirts of Denver.
Arapahoe County District Attorney George Brauchler painted a picture for jurors - 19 women and five men - of the cool night in July when 400 people filed into a cinema in suburban Aurora to be entertained, and someone came to "slaughter" them.
"One guy who felt as if he had lost his career, lost his love life, lost his purpose, came to execute a plan... He tried to murder a theatre full of people to make himself feel better," the prosecutor said, pointing at Holmes.
"Through this door is horror. Through this door are bullets, blood, brains and bodies," Brauchler said, showing images of the theatre where Holmes killed 12 people and wounded 70 at a crowded midnight screening of the Batman film The Dark Knight Rises.
"When we're done getting all these horrific details... I'm going to come back and stand in front of you, right here, and I'm going to ask you to reject that guy's claim he didn't know right from wrong," he said, his voice breaking with emotion.
Holmes, wearing glasses, a pale blue shirt and stubble, looked on impassively as Brauchler played recordings of frantic, gunfire-filled 911 calls from that night.
Holmes, 27, who was armed with a handgun, shotgun and semiautomatic rifle has pleaded not guilty by reason of insanity.
The district attorney said two court-appointed forensic psychiatrists had studied Holmes and concluded he was sane when he carried out the rampage.
"This guy has a superior intellect... he is smart," Brauchler said. He said Holmes planned to escape after the shooting, including by using spikes to puncture the tires of any police cars that chased him, but realised he was outnumbered by officers and decided to give up.
Relatives of some of the victims wept softly in court as the district attorney outlined the state's case, and Holmes' parents sat together, looking stunned.
Arapahoe County District Court Judge Carlos Samour says he expects the trial to take four or five months.
Lawyers for Holmes, who is charged with multiple counts of first-degree murder and attempted murder, concede he was the lone gunman but have said the Southern California native was in the throes of a psychotic episode when he plotted and carried out the attack.
Public defender Daniel King told jurors his client was suffering from schizophrenia, and that the defendant had not been in control of his thoughts, of his actions, "or what he perceived to be reality".
"By the time Mr Holmes stepped into that theatre, his perception of reality was so skewed, so malformed, that he no longer lived in the world we live in," King said.
He said Holmes had been pursued and commanded by "unwanted thoughts" which had entered his head and told him to kill since he was a sophomore in high school. "This is about a brain disease, a diseased mind, and about the power of psychotic delusion," King said.
"The reality is mental illness... There's no evidence he's faking anything."
Police say Holmes, dressed in a gas mask, helmet and body armour, lobbed a teargas canister into the screening at Aurora's Century 16 multiplex, then opened fire.
Brauchler said on Monday Holmes had also been listening to loud techno music on headphones at the time. The defendant first appeared in court days after the rampage looking disoriented, and with his hair dyed orange.
Holmes, who graduated with honours from the University of California, Riverside, has no criminal record.
He had been courted by neuroscience doctoral programmes, but had been seeing a school psychiatrist and withdrew from a graduate programme at the University of Colorado's Anschutz Medical Campus before the attack.
Colorado prosecutors rarely seek the death penalty, and the state has just three inmates on death row. Only one death-row inmate has been executed in Colorado in nearly 50 years.