CENTENNIAL, Colo. » After nearly 3 years of mystery, a clearer but conflicted portrait of James Holmes emerged from the first few hours of his trial in the Colorado theater shootings.

In opening statements Monday, defense lawyers portrayed him as a smiling child who enjoyed surfing with his family but who also sensed something was wrong with his mind, even at a young age.

Hoping to find a fix, he set off to study neuroscience at the University of Colorado, but mental illness propelled him to commit the bloody and terrifying attack on a suburban Denver movie theater in July 2012, defense lawyer Katherine Spengler said.

Prosecutors depicted a frighteningly smart killer who methodically planned and carried out a mass murder to make himself feel good and be remembered — knowing all the while that what he was doing was immoral and illegal.

No witnesses testified Monday, but in four hours of opening statements, prosecutors and defense attorneys revealed a wealth of details that had been kept secret for months because of the judge’s gag order.

Defense attorneys didn’t dispute that Holmes killed 12 people and injured 70 more when he slipped into a midnight premiere of a Batman movie, but say his brain was so addled by schizophrenia that it distorted his sense of right and wrong and he had no control over his actions.

It was the first disclosure of what was wrong with Holmes’ mind.

Prosecutors revealed that two court-appointed psychiatrists both found that Holmes was sane when he opened fire, chasing moviegoers up and down the aisles, shooting at them when they tried to flee.

Holmes sat quietly throughout the first day, harnessed to the floor by a cable that ran through his pants leg.

Subdued and emotionless, his demeanor never changed, even as District Attorney George Brauchler showed jurors photos of his victims — two active-duty servicemen, a single mom, a man celebrating his 27th birthday, and an aspiring broadcaster who had survived a mall shooting in Toronto, and a 6-year-old girl whose pregnant mother lost her baby and was paralyzed.

"Through this door is horror," Brauchler told jurors, showing them a photo of the open back door of the theater, the ground bloodied by wounded, escaping victims.

"He tried to murder a theater full of people to make himself feel better and because he thought it would increase his self-worth," Brauchler said.

At least one juror dabbed tears from her eyes as he spoke.

Holmes has pleaded not guilty by reason of insanity. His defense hopes jurors will agree and have him indefinitely committed to a mental institution.

Prosecutors say he was sane and should be executed.

Prosecutors will call their first witnesses Tuesday. They are expected to start by calling wounded victims to the stand.