After a three-month trial in which they were presented with thousands of pieces of evidence and testimony from hundreds of witnesses, jurors deliberated for about a day and a half, then handed prosecutors a big win. The panel of nine women and three men rejected the defense's claim that Holmes was legally insane.
Holmes showed no reaction as the lengthy, multi-count verdict was read by Arapahoe County District Court Judge Carlos Samour. The gunman stood beside his court-appointed attorneys, looking straight ahead with his hands in his pockets.
The trial now enters the punishment phase, when the jury must determine whether Holmes, 27, should be put to death or serve a mandatory life sentence with no possibility of parole.
The defense conceded that Holmes was the shooter, but presented expert witnesses who testified that the former neuroscience student was not in control of his actions because he suffered from schizophrenia and heard voices ordering him to kill.
The prosecution presented two court-appointed psychiatrists who concluded Holmes was legally sane when he plotted and carried out the July 2012 rampage at a multiplex in the Denver suburb of Aurora.
District Attorney George Brauchler said the gunman was unusually intelligent but socially inept, and harbored a long-standing hatred of humanity.
Brauchler said Holmes could not take it when he did poorly on exams at the University of Colorado, and broke up with the only girlfriend he had ever been intimate with.
The prosecution argued that Holmes' detailed preparations for the attack showed he knew what he was doing, and knew it was wrong. They presented evidence about his purchases of guns, tear gas and body armor. They also showed how he conducted online research into bomb-making so he could booby-trap his apartment before he left for the cinema.
Holmes rigged the bombs and turned loud music on the stereo, hoping someone would open the door and trigger a deadly blast. The devices were later defused by a police bomb squad.
Sobs filled the courtroom during the trial as dozens of wounded survivors testified about hiding behind plastic chairs from the hail of bullets, and stumbling over the bodies of loved ones as they fled the theater.
Brauchler showed photos of the dead during his closing argument. His voice broke and he wiped his eyes.
"That guy, sitting right there," he said, pointing at Holmes. "He did this."
When he went to Aurora's Century 16 multiplex, Holmes was dressed head to toe in a gas mask, helmet and body armor. He lobbed a teargas canister into the screening, then opened fire with a semiautomatic rifle, pump action shotgun and pistol.
He was listening to loud techno music on headphones at the time, "to block out the screams," the prosecution had said.
Holmes declined to testify in his own defense, but jurors did watch more than 22 hours of a videotaped sanity examination conducted by one of the two court-appointed psychiatrists.
In the video, Holmes confirmed most of the details of the mass shooting, including his purchase of the weapons and his plan to draw police and other first responders away from the theater by blowing up his apartment.
Brauchler, during his closing argument this week, read to the jury mundane emails which Holmes sent to his parents discussing everyday topics, including the weather and a savings account, all while he was steadily amassing "overwhelming" firepower, steel-penetrating rounds, and bomb-making materials.
Holmes, who graduated with honors from the University of California, Riverside, had no previous criminal record.
He had been courted by neuroscience doctoral programs, but had been seeing a school psychiatrist and dropped out of a graduate program at the University of Colorado's Anschutz Medical Campus in Aurora just weeks before the attack.
Days after the rampage, the defendant first appeared in the same small, windowless courtroom in Centennial, another Denver suburb. At that time, he looked wide-eyed and disoriented, and with his hair dyed red. He has put on weight since then, and his hair has returned to its natural brown color.