The 24-year old was charged with multiple counts of first-degree murder and 116 counts of attempted murder for opening fire on theatergoers in Aurora, Colo., on July 20. 12 people were killed and 58 others wounded. Holmes was also slapped with a count of possession of explosives, according to the Associated Press.
Under Colorado law, first-degree murder can be punishable by death. However, Holmes' mental capacity has been a public question since the shooting, and many believe insanity will be his only line of defense.
Three days after the theater slaughter, Holmes was brought before the court for an initial hearing, during which he appeared dazed. His head was bobbing and his eyes were often opening and closing. Police said Holmes, a Ph.D. student at the University of Colorado-Denver medical school, was being uncooperative.
With his orange-colored hair, he looked like a cartoon. Now, some think that Holmes may avoid the death penalty, or even jail time, by pleading insanity.
'Not A Get Out Free Card'
But Holmes' defense attorney may have a hard task at hand.
It is difficult for a defense to win with a "not guilty by reason of insanity defense," or NGRI, but it is possible. The insanity defense is one of last resort - averaging less than 1 percent of total felony indictments - and has a success rate of about 25 percent for those who raise such an issue, a study showed. This is a great difference from the public's perception that insanity is a cop-out method that is used often.
"This is not a get out free card," said James Silver, former federal prosecutor in Washington, D.C., and current criminal defense lawyer in Massachusetts. "It's a lengthy process. The system does everything it can to make a defendant competent to stand trial and to make sure only those suffering from the most profound mental disease or defect are found not guilty by reason of insanity."
Silver co-authored the book "Almost a Psychopath: Do I (or Does Someone I Know) Have a Problem with Manipulation and Lack of Empathy?" with Ronald Schouten, a forensic psychiatrist and associate professor of psychiatry at Harvard Medical School.
While Silver doesn't believe Holmes has any other defense but insanity at this time, he believes that the prosecution will not buy it.
"Not in a case of this magnitude," Silver said. "There is just so much pain and suffering and death."
Colorado rarely uses the death penalty.
The state's Department of Corrections website stated that the first person to be executed was convicted murderer Noverto Griego in 1890. Executions were performed by hanging until 1933, then capital punishment was administered by the gas chamber until 1967. Between 1890 and 1967 there were 77 executions in Colorado.
Gary Lee Davis, 53, was the state's first execution in 30 years, on Oct. 13, 1997. He was also the first to be executed by lethal injection, the current method of capital punishment.
The Century 16 theater was a sold out event. Scores, if not hundreds, of people were attending the midnight showing of the new Batman movie.
Former public defender David Kaplan, who heads Colorado's public defender's office, told ABC News that there are charges can probably be brought against Holmes on behalf of anyone who was in the theater that night.
"The state will need to decide how they approach all of those charges," Kaplan said.
The questions that remain are whether the state of Colorado will seek the death penalty against Holmes, and if it does so, what's the likelihood that he will be sentenced to death. While many experts think the death penalty will be sought in the case, the decision will not be made for months.
And, if Colorado, does ask for the death penalty, Holmes will have to be convicted.
"While that is obviously very likely, there is no absolute certainty in a trial," Silver said. "If he is convicted, his mental health, along with any other mitigating factors, will have to be considered. If these outweigh the aggravating factors of the crime, he might escape the death penalty. At this point, that outcome does not seem likely at all, but there is still a great deal of investigating to be done by both the state and the defense."
Testing Holmes' Competency
The full story of what went on before the deadly shooting is not yet known. The facts released to the media at this time are the number of casualties; and that four guns - including an AR15 semi-automatic rifle - were recovered, along with approximately 6,000 rounds of ammunition legally bought. Holmes' apartment was also booby-trapped, in order to kill anybody who entered. A bomb squad had to use a robot to thwart that threat. The building where Holmes lived was evacuated.
"Trying to come to a rational understanding of why people do this is difficult," Schouten said. "You have to get inside the delusion."
If Holmes' attorney moves forward with an insanity defense, competency becomes an issue in the case. Holmes must not only understand what's taking place, he must also be able to communicate with his attorney.
"A person who describes himself as the Joker and dyes his hair orange, the signs point to metal illness at this point," Schouten added.
He predicted Holmes would be sent to a facility to test his mental capacity, after which a competency hearing will follow and a decision will be made to go forward or not. Psychiatrists from both sides will be looking for malingering deception. Assessing Holmes' competency could take about two months, Schouten said. They will sift through his mental health records, get a psychological testing, and assess his personality traits and mood disorders or psychotic disorders.
It was reported that a university psychiatrist had been treating Holmes but it is uncertain at this time what he was being treated for. There have also been reports that the psychiatrist allegedly received a package from Holmes. Several media outlets have reported that the mailed package had a notebook in it with descriptions of an attack. However, court documents showed that Arapahoe County District Attorney Carol Chambers said the parcel wasn't opened by the time the "inaccurate" news reports came out.
If Holmes had in fact sent a package, it might contain clues. Schouten said very often people will reveal their intentions to a third party.
Reconstructing Holmes' Past
If Holmes is able to put forward evidence of mental instability, what prosecutors might do is reconstruct his life in the days, months and even years leading up to the crime. They might talk to schoolmates, family and friends. Prosecutors will also try to show any action Holmes took before the crime, that is buying the guns and ammunition and the gas canisters he used to stun the crowd of theatergoers.
"[This is] because you want to know everything and be able to show a jury the amount of planning, details, that went into this crime," Silver said. "They may show the video of him standing in line buying tickets, standing next to the people he was going to shoot. That's to show that he knows what was going to happen. [That's] to show his awareness of the criminality of his act."
Silver said predicts the prosecution may also show that Holmes was in the process of withdrawing from the university before the incident happened. And, if Holmes was holding a steady job and paying bills on time, he added that these are actions that show he can follow the rules. The burden will then be on the defense to show that while behaving like a normal citizen, Holmes was suffering from mental illness.