AURORA, CO — (CNN) Twelve people who’d gone to a Colorado movie theater for an evening’s entertainment never came home. Seventy who’d wanted to see “The Dark Knight Rises” found themselves wounded in an all-too-real barrage of gunfire. And one man, James Holmes, was responsible for it all.

There’s no question that Holmes walked into the crowded Aurora theater and unleashed a torrent of bullets on unsuspecting moviegoers on July 20, 2012.

What is in question is if he’ll be found guilty of the bloodshed and, if so, what penalty he’ll face.

Jurors began deliberating his fate Wednesday, one day after attorneys from both sides offered their closing arguments.

There’s no clear timetable on when a decision will be reached on Holmes and the 165 charges he faces. But when it comes, it will close a chapter in what has been a long, grueling journey — more than 11 weeks of trial, about six months after the start of jury selection, and some three years after the nightmare began for families in and around the suburban Denver community.

By virtue of his pleading not guilty by reason of insanity, the now 27-year-old Holmes has never denied he was behind the killing.

But given his mental state, his lawyers contend that he should not be found culpable.

“The evidence is clear that he could not control his thoughts, … he could not control his actions, and he could not control his perceptions,” defense attorney Dan King said during closing arguments. “… Only the mental illness caused this to happen and nothing else.”

Yet prosecutors — who called more than 200 witnesses to the stand, among them investigators, students who knew Holmes and his ex-girlfriend — insisted the shooter knew very well what he was doing. He acted deliberately, if diabolically, to deliver pain and his mental issues shouldn’t excuse him from paying the price, they argued.

“Look at the evidence, then hold this man accountable,” Arapahoe County District Attorney George Brauchler said. “Reject this claim that he didn’t know right from wrong when he murdered those people and tried to kill the others…

“That guy was sane beyond a reasonable doubt, and he needs to be held accountable for what he did.”

Having bought a ticket 12 days earlier, Holmes walked into the theater #9 screening of “The Dark Night Rises” like other patrons. He then walked out through a rear door, which he left propped open.

Just after midnight, some 18 minutes after the movie began, he — with his bright red-orange hair looking like the Joker, the Batman villain, as portrayed by late actor Heath Ledger in an earlier movie — returned wearing a ballistic helmet, a gas mask, black gloves and protective gear for his legs, throat and groin.

A tear gas canister exploded in the theater, then gunfire erupted from an AR-15 rifle, a 12-gauge shotgun and at least one .40 caliber handgun. The real-life horror story ended with Holmes’ arrest outside the theater about seven minutes after the first 911 calls were made to police.

But it wasn’t in time to save the lives of Jonathan Blunk, Alexander Boik, Jesse Childress, Gordon Cowden, Jessica Ghawi, John Thomas Larimer, Matthew McQuinn, Micayla Medek, Alex Sullivan, Alexander Teves, Rebecca Ann Wingo and the youngest victim, 6-year-old Veronica Moser-Sullivan.

During the trial, prosecutors detailed the nightmare, describing the scores of spent shells, pellets and casings, as well as the accompanying bullet holes. They played a graphic 45-minute video showing bloodied bodies scrawled across the floor and aisles, some contorted and others in fetal positions. They noted more than 200 live rounds were never fired, though it’s hard for anyone to fathom it could have been worse.

“I was like a deer in the headlights. I froze. I wasn’t able to process what was going on,” Kimberly Avra testified of her reaction before a friend pulled her to the ground. “So I sat there and stared at it (the shooter).”

Prosecutors painted a picture of a once-promising neuroscience student who knew exactly what he was doing, both carrying out the attack and rigging his apartment with makeshift explosives ahead of authorities’ arrival.

“Nothing was random,” said FBI Special Agent Christopher Rigopoulos, who was part of the evidence collection team who saw how Holmes’ apartment contained pickle jars filled with napalm and bullets linked together, plastic soda bottles filled with gasoline and other dangerous concoctions.

Those who spent time with Holmes as a PhD student at the University of Colorado Anschutz Medical Campus in Aurora described him as quiet and socially awkward, but seemingly not “detached from reality.”

Fellow student Jessica Cummiske recalled that one thing about Holmes’ eyes really stood out. “There was more than one occasion where his pupils were completely blown out. It was shocking, stunning,” she said.

In fact, defense attorneys repeatedly highlighted Holmes’ dilated eyes during cross-examination.

But this line of defense is controversial. For more than 100 years, mental health experts have studied pupil dilation, but it hasn’t yet proved to be a way to diagnose psychiatric conditions, according to Slate magazine and “The Handbook of Clinical Neurology.”

While many acquaintances, medical professionals and others weighed in on his mental state during the extensive trial, Holmes did not — declining to testify on his own behalf.

That leaves jurors to sort through all the evidence and testimony to decide for themselves if he was or was not sane.

Holmes’ lawyers never denied that their client was responsible for the mass shooting, one of the worst in U.S. history. Their argument throughout the trial was that he’d been mentally off all along.

Months before the shooting, Dr. Lynne Fenton said Holmes told her he had “homicidal thoughts” as often as three or four times a day. As his treatment progressed, he told her his obsession with killing was only getting worse.

Yet the psychiatrist explained that she didn’t place him in a psychiatric hold because he never disclosed his intention to kill or named a target. Nor did he talk about feeling manic or depressed or seeing “flickerings” or other hallucinations, as he did in a notebook Holmes mailed to her.

Dr. Jeffrey Metzner, a court-appointed psychiatrist, testified that “despite having mental disease or defect, Mr. Holmes (could) tell the difference between right from wrong.”
“It is my opinion,” Metzner said, “that Mr. Holmes, at the time of the commission of the alleged acts, met the criteria for legal sanity.”
When pressed by the defense — which addressed during the trial the depths of Holmes’ psychosis and delusions, asserting that he has schizophrenia — Metzner added that the shooting was a direct result of mental illness. Lawyer Daniel King then asked if the shooting wouldn’t have taken plane if not for Holmes’ condition.

Correct again, the psychiatrist stated.

If the jurors decide to convict Holmes on multiple murder charges, the next question would be what price he’ll pay.

Back in 2013, the prosecution signaled it would seek the death penalty.

“It is my determination and my intention that in this case, for James Eagan Holmes, justice is death,” Brauchler said then.

The shooter’s parents, Robert and Arlene Holmes, were regulars in court during their son’s trial. They were there again Tuesday, packed into the room alongside survivors and family members of some of the dead.

They have not talked to reporters. But they have written two open letters and published a prayer book detailing the family’s internal struggle and pleading for their son’s life.

In a December 2014 letter published in the Denver Post, the couple said “we have spent every moment for more than two years thinking about those who were injured, and the families and friends of the deceased who were killed, in the theater shooting in Aurora.

“We are always praying for everyone in Aurora. We wish that July 20, 2012, never happened.”

Still, while they don’t deny James Holmes was behind the carnage, the parents said they didn’t think he should have been put on trial, much less be convicted and possibly face the death penalty, given his mental state.

“(James Holmes) is not a monster. He is a human being gripped by a severe mental illness,” his parents wrote. “We believe that the death penalty is morally wrong, especially when the condemned is mentally ill.”

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