Before the shooting, Holmes was seeing a psychiatrist at the University of Colorado, Denver, where he was a first-year neuroscience graduate student. The psychiatrist became alarmed, but Holmes left the graduate program shortly after failing a year-end exam in June. Holmes was apparently never contacted by law enforcement.
During the preliminary hearing, witnesses testified that Holmes spent weeks amassing an arsenal and planning the attack, and that he took photos of himself hours before the shooting, including one that showed him grinning with a handgun.
They also detailed an elaborate booby trap set up at Holmes' apartment designed to explode at the same time the theater attack occurred several miles away.
Prosecution witnesses testified that Holmes began acquiring weapons in early May, and by July 6 he had two semi-automatic pistols, a shotgun, a semi-automatic rifle, 6,200 rounds of ammunition and high-capacity magazines that allow a shooter to fire more rounds without stopping to reload.
Defense lawyers didn't call any witnesses during the hearing.
The delay of the arraignment signals the possibility of more postponements in the case, particularly given the questions about the mental health of Holmes.
Either side in the case could contend that Holmes is not mentally competent to stand trial. If he were found incompetent, the case would come to a halt while he receives psychiatric treatment at the state mental hospital. He would remain there until doctors can restore him to competency, at which point the case would continue.
Once the judge rules Holmes is competent — either immediately after a competency hearing or after psychiatric treatment — and any other delays are resolved, Holmes would then enter a plea.
That happened with Jared Loughner in the Tucson, Ariz., shooting that killed six people and wounded 13, including then-Rep. Gabrielle Giffords. A federal judge ruled Loughner was incompetent to stand trial. After more than a year in treatment, Loughner was ruled competent, the case proceeded, and he entered guilty pleas. He is serving life in prison.
Another possibility could involve Holmes pleading not guilty by reason of insanity. In that scenario, future legal maneuvering and a trial would pivot on his mental state. If found not guilty by reason of insanity, Holmes would be committed to the state mental hospital for treatment. His case would be reviewed every six months, and he conceivably could be released if he ever is deemed no longer insane.
In any case, victims are bracing for a lengthy process.
"It's going to be a lot of waiting, but justice is going to be served," said Yousef Gharbi, 17, who spent 35 days in a hospital after being grazed in the head during the massacre.
Associated Press writer P. Solomon Banda contributed to this report.