Centennial, Colorado CNN  — 

James Holmes’ insanity defense may have failed when he was found guilty of first-degree murder in the Aurora movie theater massacre, but his attorneys will likely raise his mental illness again when they try to persuade jurors to spare his life.

The month-long penalty phase of Holmes’ trial is set to begin on Wednesday, and his mental illness should play an even more prominent role than it did when the jury was asked to decide whether his shooting rampage was an act of murder or madness.

A failed neuroscience graduate student, Holmes became one of the nation’s worst mass shooters when he opened fire three years ago at a midnight show in a crowded theater in the Denver suburb of Aurora. He killed 12 people and wounded 70 others.

A memorial with 12 crosses, one for each victim, stood outside the Century 16 multiplex on Monday, and the victims were remembered during an evening memorial service.

It is the second time this year an anniversary of a horrific crime has been observed between the guilt and penalty phases of a major capital case. In April, the Boston Marathon was held between the guilt and penalty phases for the convicted bomber, Dzhokhar Tsarnaev. The jury condemned Tsarnaev to death for his crimes.

Holmes’ jury – nine women and three men – was swift in rejecting his insanity defense, finding last week that although he is a diagnosed schizophrenic, he knew what he was doing that night, and that it was wrong.

Mental illness was not enough to spare him from responsibility for his crime. But will it save his life?

“It’s very unusual for juries to find ‘not guilty by reason of insanity’ because the legal definition is so restrictive,” said CNN legal analyst Mark Geragos. “That certainly doesn’t mean he isn’t nuts, which will play a role in the next phase of the trial.”

Prosecutors are expected to launch their case for execution by presenting powerful victim impact evidence from some of the 70 shooting survivors and grieving relatives of the 12 people who died – victims Holmes told a psychiatrist he considered “collateral damage.”

The stories of devastation and loss will be emotionally compelling, and no doubt overwhelmingly sad.

Jurors will be asked to find aggravating factors and mitigating factors, and then to weigh them. The final question they will face is daunting: If you decide in favor of the death penalty, can you morally stand behind that decision?

Colorado lists 17 possible aggravating factors that qualify for the death penalty, and it won’t be difficult for the jury to determine which ones apply to Holmes: The movie theater murders could be considered especially “heinous, atrocious, cruel or depraved,” he used weapons, he committed multiple murders and his actions endangered bystanders.

It is up to the defense to present evidence of mitigating factors – circumstances under which the penalty would be considered too harsh a punishment. The legal language is vague; mitigating factors can be found in “the character, background and history of the defendant.”

And so, the defense testimony likely will return to Holmes’ struggle with schizophrenia. The experts called earlier in the trial agreed on the diagnosis – some variety of schizophrenia – even if they disagreed over whether he was legally insane.

During the penalty phase, the defense can delve with more emotion, depth and detail into Holmes’ illness than they could while presenting an insanity defense. His parents, who have attended the trial, could be called to the stand to testify, as could former teachers, friends and others who knew him.

Colorado has executed just over 100 people in its history, but is not now considered a strong death penalty state; just one person has been executed in the state since the modern death penalty laws were enacted in 1979. The alternative is a sentence of life in prison without parole.

Still, said legal analyst Geragos, “Our death penalty history is littered with the detritus ‎of medicating the mentally ill so we can then inject them with lethal ‎medication and kill them.”

Beyond a reasonable doubt

Some 400 people had gone to the midnight premiere of the Batman movie “The Dark Knight Rises” on July 20, 2012, in Aurora, Colorado. They hoped to be entertained by a hero dressed in black, “someone who would fight insurmountable odds for justice,” as prosecutor George Brauchler told jurors.

Instead, a shooter – also dressed in black – came gunning for them. For many of the survivors, going to the movies would never again be simple or fun.

Even before the trial began, nobody disputed that Holmes was the gunman in black. And nobody disputes that he was and is severely mentally ill. But was he so sick that he couldn’t appreciate that what he was doing was wrong? So sick that he shouldn’t be convicted of murder? That was the initial question the jury faced.

In Colorado, the burden rested on the prosecution to prove beyond a reasonable doubt that Holmes was sane. Most states and the federal government place the burden on the defendant to prove insanity.

Not surprisingly, the experts called to the witness stand were divided in their opinions. Two court-appointed psychiatrists – William Reid and Jeff Metzner – said Holmes was mentally ill but sane at the time he committed the crime. He knew what he was doing, and he knew that it was wrong, they testified.

Judge Carlos Samour Jr. told jurors they should find Holmes legally insane if “he was so diseased or defective in mind at the time of the commission of the act as to be incapable of distinguishing right from wrong with respect to that act.”

Jurors were cautioned not to confuse insanity with “moral obliquity, mental depravity or passion growing out of anger, revenge, hatred or other motives and kindred evil conditions.”

In other words, there’s insanity – and then there’s just plain old evil.

Indeed, Holmes acknowledged to Reid during hours of videotaped sessions that killing was “legally wrong,” adding, “You get punished for killing.” And, he said, “It’s wrong to kill children.”

Two defense psychiatrists – including the University of Pennsylvania’s Raquel Gur, a nationally recognized expert on schizophrenia – testified that Holmes was so psychotic, his view of reality so warped, that he fit the criteria for legal insanity.

“The severe defect in his brain made him incapable of distinguishing right from wrong by societal standards,” she said.

Defense attorney Daniel King urged jurors to set aside their fears, prejudices and discomfort and confront the issue of mental illness in their deliberations. Society is not comfortable talking about mental illness, King said, and even Holmes feared the stigma enough to hide his mental illness from his family and doctors.

Holmes kept a notebook

The defense asserted Holmes has struggled with mental illness and homicidal thoughts since his early teens. By the time he opened fire, he had been battling what he called his “broken brain” for a decade. He was exhausted and only getting sicker. He had always felt something was wrong with him, according to testimony, and his studies in neuroscience may have been his way of trying to fix himself.

His childhood seemed normal, but he became withdrawn at age 12, when his family moved from Castroville to San Diego. He didn’t want to leave his friends and slid into depression. His concerned parents sent him to a therapist, and he was diagnosed with something called “oppositional defiant disorder.”

He described his battle with mental illness in a notebook he mailed hours before the shootings to Lynne Fenton, a University of Colorado psychiatrist who was treating him at a campus clinic. He had sought help for his social awkwardness; he told her about his homicidal thoughts. But, Fenton said, she saw no sign that Holmes would act on those thoughts.

The notebook wasn’t discovered until days after the movie theater massacre.

Holmes began seeing Fenton in early 2012, and by then his mental illness was winning the battle. He’d always done well in school, but he was failing. He broke up with the first girlfriend he’d ever had, and he lost his best friend at grad school. Why? Because he told them about his homicidal thoughts – the first time he’d dared articulate them to anyone.

In his twisted mind, defense attorney King said, Holmes now felt compelled to act on his homicidal impulses because he had spoken out loud about them. He had made them real.

He now viewed killing as his “mission,” King said.

Holmes bought a ticket and entered Theater 9 in the Century Aurora 16 movie complex 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.

He then opened fire with a 12-gauge pump action shotgun and then 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.

Starting about 12:30 a.m., 41 calls came in rapid succession to 911. The Aurora police station is just three minutes away, and the first officers arrived to find 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 weren’t being answered. Ten people lay dead in the theater, and two more would be pronounced dead at hospitals.

Holmes had brought 700 rounds of ammunition. Metal piercing bullets went through seats – and even through walls into Theater 8. He dressed in protective gear and took a painkiller in case he was injured during his capture by police. He feared being killed, and he did not want to feel pain.

Shooter had his own theory on actions

The defense has acknowledged that some of Holmes’ thoughts and actions might seem rational. He was able to plan intricately. But, they argued – unsuccessfully – the planning supported his primary delusion, what Holmes called his “life capital” theory.

It was spelled out in the notebook he’d mailed to Fenton. Holmes also shared details of his thinking during hours of videotaped sessions with Reid, the court-appointed psychiatrist.

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. And so, by the end of the theater shooting, Holmes believed he had raised his “life capital” to 13, adding all the qualities and experiences of the people he killed to his own.

“The dead can’t be repaired,” he told Reid. “It’s kind of irreversible.”

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.”

Prosecutor Brauchler said Holmes’ actions – dressing in protective gear and taking painkillers for fear of being shot or killed by police – sounded like the thinking of a rational person. A sane person.

But the defense argued that Holmes didn’t need to be catatonic or babbling gibberish to fit the criteria for legal insanity. Some of his actions seem sensible, until one considers they are being done to support his delusional “life capital” plan.

“His delusional process cannot be separated from him. It’s part of his being,” said defense attorney King. “You cannot divorce the mental illness from this case, or from Mr. Holmes, because the mental illness caused this to happen. Only the mental illness caused this to happen, and nothing else.”

Surely only a madman could do such a thing, to shoot into a crowded movie theater. And there’s a lot about Holmes’ story that seems, well, crazy. He dyed his hair orange, posed for selfies wearing diabolical black contact lenses, armed himself to the teeth and donned what a prosecutor called his “kill suit.” He fired metal-piercing bullets into the crowd. He would have fired more but the gun jammed. And so he walked calmly outside to his car and surrendered to police.

Brauchler said surrendering is what any rational person would do in that situation. He pointed to the uneventful arrest as a sure sign the defendant was sane at the time of the shooting. And Holmes was able to plan the attack with meticulous detail, he added. Could an insane person do that?

But just hours later, a different side of Holmes emerged at the Aurora police station. He seemed almost childish. When detectives covered his hands with paper bags to preserve gunshot residue, he played with the bags as if they were puppets. Would any sane person accused of multiple murders do that?

The defense attorneys maintained that Holmes was in the throes of a psychotic breakdown. It had been building up for a long time and had gotten progressively worse between March and late July 2012.

He exhibited some symptoms at that time, but many more emerged during the first few months he was in jail.

The psychosis was so intrusive, according to the defense experts, that Holmes’ high IQ dropped by seven points.

His condition worsened in custody

In hindsight, there may have been some red flags. Fenton and a colleague treating Holmes at the university clinic grew concerned he was headed toward a breakdown. But he stopped seeing them when he withdrew from school. And he hid aspects of his disease from them, saving his homicidal thoughts for the notebook.

The loss of his friends after he told them about his homicidal thoughts should have put Holmes on warning that society frowned on killing, that what he was planning was legally and morally wrong, Brauchler argued.

But a person in the grips of a psychotic delusion doesn’t pick up on social cues, defense attorney King countered.

Once he was in jail, Holmes was a compliant prisoner, but his mental illness worsened. He experienced what doctors believe was a psychotic break nearly five months after his arrest – on November 12, 2012.

By then, shadows and voices haunted the walls of his cell, urging Holmes not to eat, especially the red food.

He banged his head on the cell walls, raising big bruises on his forehead, and fell over backward from his bunk to the hard floor. Asked why he’d done that, he responded that he was saving his captors from himself.

He placed a paper drinking cup over his penis and tried to keep it in place as he performed a backwards somersault. The cup fell off on every try. In a video, he is seen naked, with a blanket covering his head.

He smeared feces throughout his cell and then curled into a catatonic ball on the floor, his limbs contorted and seemingly frozen at odd angles. In an ambulance, on the way to a hospital, he babbled nonsense. “You can’t teach an old dog new tricks,” he mumbled, over and over, like a mantra.

He seems better now, or at least his behavior does. He has been a passive presence during 50 days in court. But, his lawyers say, Holmes still holds on to the delusion that he can add value to his life by killing others.

CNN’s Paul Vercammen and Jack Hannah contributed to this story.