Holmes, 24, sat silently in a packed Denver-area courtroom on Monday, as a judge told him about the charges filed against him, including murder and attempted murder, in one of the deadliest mass shootings in recent U.S. history.
After the charges were read, prosecutors and defense attorneys sparred over whether a notebook that news reports said Holmes sent to his psychiatrist and had descriptions of the attack was privileged information.
It's an argument that foreshadows one of the case's most fundamental issues: Does Holmes have a mental illness and, if so, what role did it play in the shooting that left 12 people dead and 58 others injured?
Sam Kamin, a law professor at the University of Denver, said there is "pronounced" evidence that the attack was premeditated, which would seem to make an insanity defense difficult. "But," he added, "the things that we don't know are what this case is going to hinge on, and that's his mental state."
In all, prosecutors charged Holmes with 142 counts in the shooting rampage at a midnight showing of the new Batman movie.
Holmes faces two first-degree murder charges for each of the 12 people killed and two attempted first-degree murder charges for every one of the 58 injured in the July 20 shooting.
The maximum penalty for a first-degree murder conviction is death. The multiple charges expand the opportunities for prosecutors to obtain convictions.
"It's a much easier way for the prosecution to obtain a conviction," said Denver defense attorney Peter Hedeen. "They throw as many (charges) up as they can. If you think you can prove it three different ways, you charge it three different ways."
Unlike Holmes' first court appearance July 23, Monday's hearing was not televised. At the request of the defense, District Chief Judge William Sylvester barred video and still cameras from the courtroom, saying expanded coverage could interfere with Holmes' right to a fair trial.
A shackled Holmes did not react as the charges were read. At one point, Holmes, his hair still dyed orange-red, leaned over to speak with one of his lawyers and furrowed his brow. When the judge asked him if he was OK with postponing a hearing so his team could have time to prepare, he said softly: "Yeah."
Some court spectators Monday wore Batman T-shirts. Several people clasped their hands and bowed their heads as if in prayer before the hearing. At least one victim attended, and she was in a wheelchair and had bandages on her leg and arm.
Jessica Watts, whose cousin Jonathan Blunk was killed in the shootings, said in a written statement that she believes in the justice system. "He will be held accountable for his actions and we, Jonny's family, will continue to mourn the hole we now have in our lives," she said.
For the murder charges, one count included murder with deliberation, the other murder with extreme indifference. Both counts carry a maximum death penalty upon conviction; the minimum is life without parole.
In addition, Holmes was charged with one count of possession of explosives and one count of a crime of violence. Authorities said Holmes booby trapped his apartment with the intent to kill any officers responding there the night of the attack.
A conviction under the crime of violence charge means that any sentence, including life terms, would have to be served consecutively, not concurrently, said Craig Silverman, a former chief deputy district attorney in Denver.
That ensures that if laws change in the future, the person convicted would still serve a lengthy sentence, Silverman said.
Analysts expect the case to be dominated by arguments over the defendant's sanity.
Under Colorado law, defendants are not legally liable for their acts if their minds are so "diseased" that they cannot distinguish between right and wrong. However, the law warns that "care should be taken not to confuse such mental disease or defect with moral obliquity, mental depravity, or passion growing out of anger, revenge, hatred, or other motives, and kindred evil conditions."
Holmes' public defenders could argue he is not mentally competent to stand trial, which is the argument offered by lawyers for Jared Loughner, who is accused of killing six people in 2011 in Tucson, Ariz., and wounding several others, including U.S. Rep. Gabrielle Giffords.
If Holmes goes to trial and is convicted, his attorneys can try to stave off a possible death penalty by arguing he is mentally ill.
Prosecutors will decide whether to seek the death penalty in the coming weeks.
Defense attorney Tamara Brady said Monday she will subpoena University of Colorado, Denver, psychiatrist Lynne Fenton, whom Holmes had been seeing, to testify in a dispute over whether the notebook is privileged because of a possible doctor-patient relationship.
Arapahoe County District Attorney Carol Chambers disputed news reports that the notebook contained descriptions of an attack.
On Friday, court papers revealed that Holmes was seeing Fenton. They did not say how long or if it was for a mental illness or another problem. An online resume listed schizophrenia as one of Fenon's research interests.
Holmes' public defenders want to know who leaked the information to the news media. Prosecutors say the notebook was inside a package Holmes reportedly sent to Fenton at the university. Holmes came to the school's competitive neuroscience doctoral program in June 2011 and dropped out a year later.
Authorities seized the package July 23, three days after the shooting, in the mailroom of the medical campus where Holmes studied. A hearing on the matter was set for Aug. 16.
Sylvester set an Aug. 9 hearing on news organizations' motion seeking to unseal the case docket.
Sylvester has tried to tightly control the flow of information about Holmes, placing a gag order on lawyers and law enforcement, sealing the court file and barring the university from releasing public records relating to Holmes' year there.