Centennial, Colorado (CNN) It is a rare glimpse into the origins and psyche of a mass shooting. And it is completely unsettling.

The capital murder trial of James Eagan Holmes has, for more than a week, been taking a jury inside the "broken" mind of a young man who really didn't like other people. Prosecutors say Holmes should pay with his life for the killings of eight men, three women and a little girl at a Colorado movie theater nearly three years ago.

Hours of tape-recorded sessions with a psychiatrist appointed by the court to evaluate his sanity have become part of the evidence as well as a notebook in which Holmes sought to explain his actions

Holmes hasn't taken the witness stand, but he might as well have. His videotaped voice, flat and monotonous, has filled the suburban courtroom here.

After weeks of gruesome and emotionally gripping testimony, the focus of Holmes' trial shifted in week six from the carnage to the man prosecutors hold responsible for it -- and to the central questions in this case:

What was Holmes' state of mind on July 20, 2012, when he opened fire at the midnight showing of the Batman movie "The Dark Knight Rises" at the Century 16 multiplex in the Denver suburb of Aurora. Was he sane or insane?

The jury's answers to these questions could very well determine whether the 27-year-old former grad student is executed or spends the rest of his days in a Colorado prison or mental hospital.

Most defendants testify to try to save themselves. But Holmes' words are providing the pillar for the prosecution's case against him.

"The mission" is how Holmes referred to the shootings that killed 12 and wounded 70. After 22 hours of sessions, court-appointed psychiatrist William Reid concluded that Holmes was mentally ill but legally sane.

He invoked a diagnosis unfamiliar to most laymen: schizotypal personality disorder. In other words, the expert said, Holmes was indeed sick and anti-social, but he was rational.

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The defendant acknowledged to Reid that shooting people is "legally wrong."

"You get punished for killing," Holmes said.

He also stated with conviction, "It's wrong to kill children."

And yet ...

Holmes bought a ticket for "The Dark Knight Rises" and entered Theater 9 around midnight, choosing a front-row seat. He pretended to take a phone call and left through an emergency exit, propping the door open with a plastic doorstop. He returned 18 minutes into the movie, tossing a tear gas grenade into the audience. As panicked moviegoers scrambled for the exits, he fired a 12-gauge pump action shotgun into the seats, then opened fire with an AR-15 style semi-automatic rifle with a high-capacity clip that jammed. He also fired several shots with a Glock 40-caliber pistol.

The first of 41 calls to 911 came in at about 12:30 a.m., reporting explosions and 10 to 20 shots fired, with people down. The police station is close by, and the first officers arrived about a minute later. They were greeted by a horrific scene: Blood, body tissue and spilled popcorn were everywhere, the air was filled with tear gas and gun smoke, and panicked people were screaming. Cell phones were going off, but nobody was answering them. Ten people lay dead in the theater, and two more were pronounced dead at hospitals.

Thirty-three shots found their mark: Four struck 6-year-old Veronica Moser-Sullivan, and six found a 24-year-old aspiring sports journalist, Jessica Ghawi, who had narrowly missed a deadly mass shooting a few weeks earlier at a Toronto food court.

Photos: Colorado shooting victims Jonathan T. Blunk, 26, served for five years in the U.S. Navy. He died shielding a friend from the gunfire inside the theater. Hide Caption 1 of 12 Photos: Colorado shooting victims Alexander J. Boik, 18, was remembered by friends and loved ones as a "great person" whose "craziness touched hundreds," according to a Facebook page created in his memory. Hide Caption 2 of 12 Photos: Colorado shooting victims Air Force Staff Sgt. Jesse E. Childress, an Air Force reservist, was a cybersystems operator on active duty. He was 29. Hide Caption 3 of 12 Photos: Colorado shooting victims Gordon W. Cowden, 51, took his two teenage children to the theater. His children escaped unharmed. Hide Caption 4 of 12 Photos: Colorado shooting victims Jessica Ghawi, 24, was an aspiring sports reporter. She grew up in Texas before moving to Denver to try break into the television market there. Hide Caption 5 of 12 Photos: Colorado shooting victims Petty Officer 3rd Class John Thomas Larimer, 27, served in the Navy like his father and grandfather. He had been in the service for about a year. Hide Caption 6 of 12 Photos: Colorado shooting victims Matthew R. McQuinn, 27, died trying to provide cover for his girlfriend, Samantha Yowler, during the shooting, according to a family attorney. Yowler survived. Hide Caption 7 of 12 Photos: Colorado shooting victims Micayla C. Medek, 23, known to her friends as Cayla, was "very spiritual and close to God," cousin Anita Busch told CNN. Hide Caption 8 of 12 Photos: Colorado shooting victims Veronica Moser Sullivan, 6, was the youngest victim of the Aurora theater shooting. She had just learned how to swim. Hide Caption 9 of 12 Photos: Colorado shooting victims Alex M. Sullivan, 27, went to the movie to celebrate his birthday with his wife, two days before their first wedding anniversary. Hide Caption 10 of 12 Photos: Colorado shooting victims Alexander C. Teves, 24, recently graduated from the University of Denver with a master's degree in counseling psychology. He died protecting his girlfriend. Hide Caption 11 of 12 Photos: Colorado shooting victims Rebecca Ann Wingo, 32, joined the Air Force after high school, became fluent in Mandarin and served as a translator, according to CNN affiliate WFAA. Hide Caption 12 of 12

Holmes told Reid, the court-appointed psychiatrist, that he felt remorse, especially about the little girl's death.

"I think it's wrong to kill children," he stated. "I chose to minimize child fatalities by choosing a midnight showing of a PG-13 movie," he explained. "I felt sad that a child had died. It wasn't my intention to kill children or leave them parentless."

In Holmes' skewed worldview, each life he took was worth a point, adding value to his own life. If his life had value, he reasoned, he wouldn't have to kill himself. But he said he never wanted to build life points by taking the lives of children.

By the end of the movie theater shooting, Holmes believed he had raised his "life capital" to 13, while an ordinary person's would simply be worth a single point.

"The dead can't be repaired," he told Reid. "It's kind of irreversible." Instead, he said he absorbed their life experiences as well as their hopes and dreams into his own life.

He had accomplished his mission, even if getting arrested was the price he had to pay. But he said he gained nothing from injuring people or leaving them behind to grieve for the dead. He spoke of the 70 people wounded as "collateral damage."

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Holmes sat down with Reid last summer after entering his insanity plea. The defense has objected to Reid's testimony, saying it violates Holmes' Fifth Amendment right against self-incrimination. But Judge Carlos Samour has twice turned down defense demands for a mistrial, saying Holmes' attorneys should have raised the issue before Reid took the stand.

More insights into Holmes' psyche -- some little more than disjointed ramblings -- are contained in a composition book he mailed to the office of Lynne Fenton, a psychiatrist who was treating him at a campus clinic at the University of Colorado's Anschutz Medical Campus in Aurora.

He sent the notebook the day before the shootings, seeking to explain how and why he had done it. It was important to him that people understand, Holmes later told Reid.

The notebook was found unread in a mail bin and seized by police. It is dedicated to "Goober, Chrissy and Bobbo" -- pet names for his mother, sister and father -- and includes the message, "Love yuhs."

One lengthy passage bears the title "Insights into the Mind of Madness." It posits questions about life and death, and contrives a formula under which the two seem to cancel each other out. An odd symbol resembling a combination of an infinity sign and the face of a space alien appears three times in the notebook.

Holmes referred to the symbol as "Ultra-ception," explaining the meaning: "Any problem can be solved with death."

"What is the meaning of life?" he asks. "What is the meaning of death?"

The word "Why?" is written over and over, covering seven pages.

But the notebook includes many signs of lucidity as well, demonstrated by Holmes' ability to plan the attack and carry it out. There is a logic, even if it seems warped. His thoughts, however off, hold together, Reid noted. They aren't scattered or disorganized.

Holmes rejected using bombs as well as chemical or biological agents as his weapons. They were too complicated. He might blow himself up. He thought about serial killings but ruled them out, again listing his reasons: "too personal, too much evidence, easily caught, few kills."

He focused instead on a mass shooting, mostly because he believed he could actually pull it off with "maximum casualties." He rejected carrying out his mission at an airport -- too much security. Instead, he chose a movie theater because it would be crowded and there would be a limited number of exits. He seems to have spent considerable time "casing the place" and sketching detailed maps into the composition book.

Holmes faces 166 counts, almost all alleging murder or attempted murder. The murder counts carry a possible death penalty. Holmes had offered to plead guilty in exchange for a life sentence, but Arapahoe County District Attorney George Brauchler rejected any plea deal, stating, "For James Eagan Holmes, justice is death." Prosecutors said they spoke with some 800 shooting survivors and family members of the 12 people slain before deciding to seek the ultimate penalty for Holmes.

Holmes pleaded not guilty by reason of insanity, and the court appointed two psychiatrists to conduct independent evaluations; both concluded he was sane, Brauchler told jurors in his opening statement.

In many states, it is left to the defense to prove insanity. But in Colorado, prosecutors bear the burden of proving a suspect sane. They must show that Holmes knew what he was doing was legally and morally wrong.

Reid videotaped his sessions with Holmes, some 22 hours in all. Most of the recordings were played last week in court.

As the trial's focus shifted in the sixth week of testimony to Holmes, the seating area reserved for shooting survivors and relatives of the dead thinned noticeably. Sandy Phillips, the mother of Jessica Ghawi, said it was difficult to hear Holmes attempt to justify what he has done.

"It's excruciatingly painful. He's so devoid of any human kindness, expression, empathy. That's hurtful," she said. "When you're considered collateral damage as a parent who has lost their child in the theater, that's hard to sit and listen to."

Her husband, Lonnie, agreed. "It's adding insult to injury when you have to go through this. He decided he wanted to live. He didn't want the pain and misery. He wanted to protect himself, and it's all about him."

It is disconcerting to see Holmes, dressed in street clothes, sitting stiffly at the defense table under a screen showing him sitting just as stiffly in jailhouse blues. On the screen, he speaks with Reid, who recorded his interviews with Holmes last summer. Holmes speaks in short phrases, volunteering little information.

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In court, Holmes swivels in his chair but otherwise shows little animation. He parents sit stoically, several rows back. His father, Robert, a mathematician with degrees from Stanford University and the University of California, Berkeley, chews on his fingernails. His mother, Arlene, a nurse, looks straight ahead, occasionally writing in a notebook.

It's first time the public has heard Holmes talk about the now-infamous mass shooting, one of the worst in recent history. After his arrest, he ended police questioning after eight minutes by asking for a lawyer.

To some he comes across as cold, to others he seems completely disconnected.

It is unusual for a suspect in a mass killing to survive and go to trial, much less describe an attack in detail. Usually, the suspects die by their own hand or are killed by police, an outcome popularly known as "suicide by cop." But Holmes meekly surrendered to police in the parking lot outside the theater.

And so, earlier this week, the jury heard him describe what it was like to walk into a packed movie theater, toss a tear gas grenade into the crowd and open fire. Jurors also heard him explain why he felt he had to do it. The victims had to die, Holmes said, so he wouldn't.

He told Reid about gearing up, donning bullet-proof pants, gloves and a gas mask and slinging the AR-15 rifle over his shoulder, tucking the Glock into his belt and picking up his loaded shotgun. He said he couldn't see well in the dark because of the gas mask.

As he stepped out of his car outside the theater, he said he called a mental health hotline at the university. It was one last chance to "stop the mission" and back out.

But no one picked up the phone.

Even if someone had tried to talk him down, Holmes said, he or she likely would have been "overruled." He waited nine seconds and then grew certain that the mission was a go.

"It was really going to happen," he said.

He felt "calm and collected" as if he was on "autopilot" as he started shooting. He knew he was well-prepared.

He doesn't remember hearing gunshots or panicked screams; he had techno music blasting through the ear buds he wore. He didn't view his targets as people. He didn't even know them, he said. They were just "amorphous" numbers, sacrifices to his peculiar point system.

Jurors have also learned about Holmes' family and what makes him tick. He has believed since he was a teenager that his mind was "broken." He said he had been obsessed with killing for more than a decade. Brauchler said in his opening statement that Holmes killed to make him feel better about himself after a series of personal setbacks, including failing at school and breaking up with his girlfriend.

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Holmes wrote in his notebook that he studied neurology in college and grad school in a failed attempt to fix his own "broken mind."

His childhood was haunted by night terrors in which "Nail Ghosts" hammered on the walls. Shadows and "flickerings" danced in his peripheral vision. He has been depressed and obsessed with murder since about age 14, he says, because it was the only viable alternative to suicide.

No voices commanded Holmes to kill. The idea was completely his own, he told Reid.

"I'd say I was on my own authority."

He said he considered carrying out the mass shooting at the movie theater since the day he bought the shotgun -- May 28, according to court records.

He listed a host of physical maladies -- from schizophrenia to Asperger's to restless leg syndrome -- in a section called "Self-Diagnosis of a Broken Mind." He complained of fatigue, catatonia, insomnia, social awkwardness and isolation, hyperactivity and problems with his eyes, ears, nose -- "constant dripping" -- and even his penis, which he said he injured as a child. He studies himself and his "physical shortcomings" in the mirror obsessively.

But perhaps the biggest symptom of his broken brain, he said, was the difficulty he has forming his thoughts into words. He simply cannot communicate, and contact with other human beings makes him very uncomfortable. It feeds his hatred for "humanity."

He struggles with an "odd sense of self," waging a constant battle between his "real self" and his "biological self."

He noted that he had recently "lost" the battle by allowing himself to fall in love.

"So always, that's my mind," he wrote. "It is broken. I tried to fix it. I made it my sole conviction but using something that's broken to fix itself proved insurmountable."

He pursued knowledge as a cure, but it didn't work.

"Neuroscience seemed like the way to go but it didn't pan out. In order to rehabilitate the broken mind, my soul must be eviscerated. I could not sacrifice my soul to have a 'normal' mind."

He said he "fought and fought" until the end. To relieve his personal torture, he sought to escape by distracting himself or ignoring the problem. Still, his depression and low opinion of himself persisted.

And so, in the end, he made a choice and noted it in his composition book: "The last escape, mass murder at the movies."