Feature: Colorado mass murder shooter trial begins

It was a riveting first day in the mass murder trial of James Holmes, as a packed courtroom heard opening statements in the most significant American trial in 20 years.

Holmes has pleaded guilty by reason of insanity to killing 12 and injuring 58 unsuspecting moviegoers with gunfire at the midnight showing of a Batman movie in the summer of 2012. He faces 166 counts of murder and attempted murder.

Both defense and prosecution attorneys exposed the crux of their positions, with the prosecution citing numerous reasons why Holmes was sane at the time of the shooting, including opinions of two qualified psychiatrists and his "meticulous" pre-mediated planning of killings.

The defense argued that Holmes, who suffers from severe schizophrenia, has been mentally ill for years, and was peaking with his illness when he entered the back of the Century 16 movie theaters with four guns and hundreds of bullets.

If found insane, Holmes will spend the rest of his life in jail. If found sane, he faces execution.

Arapahoe County District Attorney George Braucheler's two-hour remarks painted Holmes as a brilliant, "high IQ" Ph.D. candidate who "tried to murder a theater full of people because he thought it would make him feel better."

The defense, led by Daniel King, spent two hours detailing the depth and severity of Holmes' schizophrenia, and how it affected his judgment prior to the shooting.

"When James Holmes stepped into that theater in July 2012, he was insane," King told the jury. "His mind had been overcome by a disease of the brain that had plagued him for years."

For the first time since the July 20, 2012 shooting, the contents of Holmes' "notebook" was revealed.

Holmes sent his psychiatrist the notebook the day before the shooting. It showed the extent of his insanity and his general hatred of humanity.

Also revealed for the first time was that Holmes had entertained thoughts of killing people since he was 13, that he took the drug Vicodin just before the shooting, and that he was blasting techno music through his protective gas mask while he fired bullets into the unsuspecting crowd.

Public defender Katherine Spengler told jurors that Holmes' reason for opening fire in the Aurora theater might not be satisfying them.

"He is sick," she said. "He wants to be stopped but can't be stopped," Spengler noted, referring to Holmes' delusional belief that killing others would somehow help him.

Spengler said her client reached out for help constantly and saw his University of Colorado psychiatrist Lynne Fenton even as he amassed firearms, bullets and bomb-making materials just prior to the shooting.

The stirring statements triggered emotional responses from many in the courtroom, including friends and family of the victims, members of the media, and two of the 19 female jurors, who all teared up.

The defense relied on a powerful speech by King, likening schizophrenia to cancer, and Spengler detailing Holmes' family history of mental illness, his early signs of the condition, the "triggering" events that precipitated his act, and his behavior after the event, that support the theory he suffers deeply from the disease.

Others were not so convinced.

"It's a hoax...I don't believe him," Marcus Weaver, 44, said after the proceedings. Weaver, who was wounded by a shotgun blast to the left shoulder, held his friend Rebecca Wingo, 32, mother of two, in his arms as she bled to death in the theater.

"You have no idea what Christmas is like in her house...so many tears," Weaver told Xinhua. "He (Holmes) is very smart, very calculated, and he is guilty," Weaver said. "His justice is in God's hands."

Judge Carlos Samour Jr. said the trial may last through September.

Both sides played videos to influence jurors, who will decide whether Holmes is sent to a mental hospital or death row.

Brauchler showed a theater surveillance camera pic of 6-year-old Veronica Moser-Sullivan walking past the concession stand at the Century 16 multiplex with her pregnant mother.

It was taken "moments before he shot her four times -- four times!" yelled Brauchler to the jurors.

King showed jurors a video of a naked Holmes months after the shooting running headfirst into a concrete cell wall, falling backward and collapsing onto the ground.

"Mr. Brauchler said he did this for notoriety," King said. "Look at the video and you tell me if you would do this for the notoriety."

Brauchler told the 12 jurors and 12 alternates that Holmes wrote in his notebook a "longstanding hatred of mankind" and a year long obsession to kill."

A video of Holmes from last year saw him saying: "The dead can't be repaired or come back to life or be normal again; it's irreversible. You take away life and your human capital is limitless."

"And the wounded? Holmes was asked." "They're like collateral damage, I guess," he said without emotion.

King argued that this admission is the delusional thinking of a deeply sick young man, quoted Holmes as saying "I have fought for years to overcome my biology."

"In the end, he lost that struggle with his mind to a disease, a disease called schizophrenia," King said.

The Holmes trial is considered the biggest since those of O.J. Simpson and Timothy McVeigh, both in 1995. Endi