Hours later, investigators found his apartment booby-trapped with potentially deadly explosives, police said.
In previous hearings — many witnessed by victims and survivors — Holmes' appearance and behavior ranged from bizarre to unremarkable. On his first day in court, his hair was a shocking orange-red, his face was covered with stubble and he seemed to be in a daze.
By last week, his hair was a natural-looking brown and he wore a full beard. He sat quietly and seemed to be aware of the proceedings.
Holmes could get the death penalty or life in prison without parole if he goes to trial and is convicted of murder. He could avoid the death penalty if his lawyers argue he is mentally ill or innocent by reason of insanity.
Holmes' mental health is expected to be a major factor whether his case ends in a plea agreement or goes to trial.
His lawyers have told the judge that Holmes was mentally ill, and court records indicate they may call witnesses in the preliminary hearing to testify about his mental health. The defense team has not said whether Holmes would enter an insanity plea.
An insanity plea is different from the competency argument used for Jared Loughner, who pleaded guilty to killing six people and wounding 13, including then-Rep. Gabrielle Giffords, in Arizona in 2011.
A judge ruled in May 2011 that Loughner was mentally incompetent to stand trial and ordered him to undergo psychiatric treatment. After Loughner spent more than a year in treatment, the judge ruled he had become competent, and Loughner accepted a plea agreement that carried a sentence of life in prison without parole instead of execution.
The decision on whether to seek the death penalty will be up to the new district attorney for Arapahoe County, George Brauchler, who was elected in November and takes office Tuesday, after the preliminary hearing begins. Brauchler has not indicated what he will do.
A spokeswoman for outgoing District Attorney Carol Chambers, who oversaw the filing of charges against Holmes, declined to comment.
If prosecutors do not seek the death penalty, and if Holmes is convicted of or pleads guilty to first-degree murder charges, he would face a mandatory sentence of life without parole.