The terror from within: What drives a 'perfect' boy to kill?

Centennial, Colorado (CNN)It's déjà vu all over again. One by one, neighbors, teachers, coaches, classmates and teammates are stepping up to a witness stand to share their memories of a "perfect kid."

They describe a quiet, sweet-natured, respectful boy who did well in school, got along with others and was kind to those less fortunate.
A few months ago, the good boy's name was Jahar.
This one is being called Jimmy.
    The 13th Juror

    With the experienced eye of a trained observer and an avid trial-watcher's curious mind, Ann O'Neill is "The 13th Juror" for CNN's audience. Follow @AnnoCNN on Twitter daily.

    These boys, Dzhokhar "Jahar" Tsarnaev and James "Jimmy" Holmes, grew up to do horrible, unspeakable things. They killed strangers in places where people seek enjoyment, leaving others bloodied, broken and maimed. They made simple pleasures frightening, scarring communities once secure in the belief that "bad things don't happen here."
    Both boys had parents who wanted nothing more than for them to succeed and live out the American dream. But the boys felt out of place as they entered their teens, and eventually lashed out with unspeakable violence. For Jimmy and Jahar, the dream died before they reached 25.
    They now stand convicted of committing multiple murders deemed especially cruel, heinous and depraved. And they are becoming poster boys for the death penalty at a time when some states are declaring moratoriums and the method of execution is being challenged in the courts.
    For all their similarities, there is one glaring difference between these two capital cases. While Tsaraev's crime was cloaked in terrorism and what a judge called "the siren song" of martyrdom in the name of radical Islam, Holmes' story will focus on mental illness. It is the terror from within.
    We know what happened to Jahar Tsarnaev. His jury was unmoved by the photos of the cute little boy with the big brown eyes, or the fact he was helpful at school, attended a prom for the special ed kids and was nicer to girls than some of his friends.
    Voices of Aurora: Coping with grief, conquering life
    voices of aurora orig nws_00003402


      Voices of Aurora: Coping with grief, conquering life


    Voices of Aurora: Coping with grief, conquering life 04:13
    He awaits his death sentence, locked away in isolation at the federal Supermax prison, a 90-minute drive south of the courtroom where Holmes and his lawyers are appealing to jurors' mercy.
    Tsarnaev was tried, convicted and condemned in a federal court in Massachusetts, where there is no state death penalty. Holmes' case is unfolding in a state court in Colorado, which has the death penalty on the books, but seldom uses it.
    Neither state has held an execution in a generation.
    Holmes has been convicted of 24 counts of first-degree murder. No one questions that he suffers from schizophrenia. No one questions that his illness is severe. It wasn't enough for a successful insanity defense, perhaps, but his lawyers are far from finished.
    At this stage of the trial, when punishment is determined and mercy is granted or denied, the focus shifts from the crime to the man who committed it. The seats reserved for the families of the dead and wounded were empty as the defense took control of the courtroom narrative.
    "This phase will be, in its entirety, all about the person who committed these horrors, these aggravated murders," prosecutor George Brauchler said. "When he was a child, he had an uneventful life," he added, ticking off the things that later went wrong for Holmes: "One love lost, one school lost, one career lost."
    "When things didn't work, the crime took place," the prosecutor said.
    The jury already has found that Holmes deliberately opened fire during the first moments of July 20, 2012, at a crowded movie theater in suburban Aurora. He intended to kill, and he acted with extreme indifference for the value of human life.
    He wasn't out of his mind, jurors determined; he knew what he was doing was wrong.
    "We accept your verdicts," defense attorney Rebekka Higgs told jurors on Thursday, after they found that the cruelty of the murders qualified for the ultimate punishment.
    It is possible to be legally sane but seriously mentally ill, Higgs said. "But for his mental illness, this crime never would have occurred. It's not a justification or an excuse, but a reason to choose life."
    And so, the defense is pulling out all the stops to humanize Holmes. It brought 18 witnesses from California to Colorado to talk about his wonder years.
    "You're going to hear about Mr. Holmes' life from the beginning because you are now responsible for that life," Higgs told the jury. "And you need to know everything about that life."
    Ten of the witnesses took their turns before the jury, until a juror fell ill. The jury was sent home Friday, but the testimony continued, captured on video to be shown later.
    The witnesses described a polite, mellow kid who seemed to enjoy an idyllic childhood with parents who were loving, supportive and engaged. There were piano lessons and soccer and basketball practices.
    The haunted house the Holmes family created in their garage each Halloween was a hit in the Oak Hills neighborhood near Castroville, California. The small agricultural community is known as "The Artichoke Capital of the World."
    There were big neighborhood parties on Christmas and July 4, and kids roamed freely across unfenced back yards. Holmes was one of a group of boys who had the run of the place. In the photographs, he is smiling. He seems happy.
    Listen to what people who once knew Holmes and his family had to say:
    "He was a normal kid. He was very popular, a very bright student. The other kids liked to play with him. He was good in sports," said Suzanne Jimenez Diaz, a secretary at Castroville Elementary School.
    "He was a gentleman. He was sweet. He just had a nice, mellow mannerism to him," said Martin Thomas Barrett, a neighbor from Oak Hills. He said Holmes was one of a pack of about 15 neighborhood boys, including his sons, who played together. "It seemed like all those boys were having a great childhood," he added, saying Holmes seemed "extremely happy" as a boy of 9 or 10. He described Holmes' parents, Robert and Arlene, as "superparents."
    "He was a very nice kid, very fun to be around. He was just there having fun with everyone else," said Barrett's son, Joseph, who went by the childhood nickname of "Jo-Jo." Joseph Barrett is now an attorney in Las Vegas.
    "He was a good student and I thought he had potential," said his former piano teacher, Claire Ann Vincent. She said she was sorry to lose him when the Holmes family moved to San Diego as he reached the age for middle school.
    "He was a good boy," said middle school band teacher James Gerald Posteraro. Holmes traded the piano for a trumpet. He didn't seem to have trouble fitting in, and he received straight As and high marks for effort and citizenship.
    "I remember a very funny, very sweet, quiet kid who kind of flew under the radar," said Patrick Silva, who played soccer with Holmes during middle school and high school. "I didn't have anything bad to say about him on the field, and I don't give my respect willy-nilly."
    "He was pretty much a model child," said Barbara Stop Martin, a neighbor in San Diego who hired Holmes for yard work when he was 17. She said he worked hard and did everything he was asked to do.
    But, Holmes wasn't as social in San Diego as he had been in Castroville. By the end of middle school, he began to withdraw. Classmate William Tyler Reese recalled him as a group of five "quiet guys" who ate lunch together in the cafeteria, went to movies and played paintball.
    "I would say he was a 'by himself' kind of guy," said Thomas James Oliver, who taught Holmes in advanced history and English classes in high school. "Jimmy was really tough to get to know." He doesn't remember him having friends.
    He had won medals in cross-country as a child, but by the time he got to high school, Holmes didn't have the stamina or form to succeed, said his coach, Lori Villareal Godwin. He usually came in last, but he kept coming to practice.
    She described Holmes as "a shadow figure." She never saw him smile and found his social awkwardness "painful." He kept his head and eyes down and gave off a vibe: "I can see you but please don't talk to me." He seemed to be "in his own little world."
    "He was part of us, but not part of us," Godwin said. "If I didn't take roll, I probably wouldn't even know he was there." He was so shy that she wondered if he had a learning disability. But, she added, other students told her Holmes was "crazy smart."
    Crazy smart. Is that what happened to the model child, the happy boy?
    By high school, Holmes was struggling with his "broken brain" and having thoughts about killing people, he revealed in a notebook he mailed to a psychiatrist hours before going on his killing rampage.
    None of the people who has testified so far mentioned seeing signs of serious mental illness. That evidence is yet to come, and according to the defense, it is the key to the argument for mitigation.
    "The only reasonable explanation here is a psychotic break, a broken mind," said defense attorney Higgs. All the elements that made his crime especially heinous "were born of disease," she told jurors, saving her most dramatic argument for last:
    "We don't kill people for being sick."