James Holmes, who killed 12 people and injured 70 others when he opened fire in a packed Colorado cinema in July 2012, has been found guilty of murder.
James Holmes, 27, was found guilty on 24 counts of murder and multiple counts of attempted murder for the massacre at a Batman premiere in Aurora.
The man had pleaded not guilty due to insanity – his defense said he was controlled by his schizophrenia.
Prosecutors have said they will now seek the death penalty.
The panel of nine women and three men rejected the claim that James Holmes was legally insane.
Dressed in a blue shirt and cream-colored trousers he showed no emotion as Judge Carlos Samour took an hour to read through each of the 164 charges for murder and attempted murder, plus one count of possession of explosives.
During the 49-day trial with more than 250 witnesses, the court heard James Holmes entered the cinema in Aurora where The Dark Knight Rises was being screened, armed with an assault rifle, a shotgun and a pistol.
There were 400 people in the screening when Holmes, dressed head-to-toe in black body armor, entered through an emergency exit and appeared by the screen.
James Holmes’ victims included two servicemen, a man celebrating his 27th birthday and an aspiring broadcaster who had survived a mall shooting in Toronto. Several died shielding friends or loved ones.
The youngest killed was a 6-year-old girl whose mother suffered a miscarriage and was paralyzed in the attack.
On July 14, prosecutor George Brauchler ran through an account of the massacre.
Referring to the cinema-goers, he said: “They came in hoping to see a story of a hero dressed in black, someone who would fight insurmountable odds in the name of justice and trying to protect others.
“Instead a different figure appeared by the screen dressed all in black.
“And he came there with one thing in his heart and in his mind – and that was mass murder.”
James Holmes’ defense lawyer Dan King said his client had “lost touch with reality” and said “mental illness caused this to happen”.
He had been presented as a promising student studying for a PhD in neuroscience at the University of Colorado, having graduated from the University of California at Riverside.
James Holmes had no previous criminal record.
His defense called a pair of psychiatrists, including a nationally known schizophrenia expert, who concluded Holmes was psychotic and legally insane.
But two state-appointed doctors found otherwise. They testified that no matter what James Holmes’ mental state was that night, he knew what he was doing was wrong.
The prosecution argued that James Holmes’ detailed preparations, including the booby-trapping of his apartment with explosives before he left for the cinema, showed an awareness of what he was doing.
James Holmes was pictured at his first court appearance looking disorientated with dyed red hair in an apparent reference to Batman villain the Joker.
Deciding on James Holmes’ punishment could take the rest of the summer, Judge Carlos Samour has said.