Prosecutors filed formal charges Monday against Colorado shooting suspect James Holmes, who is accused of killing 12 people and wounding 58 others at a midnight movie screening.

Holmes has been charged with 24 counts of first-degree murder and 116 counts of attempted murder related to the shooting rampage in the Denver suburb of Aurora.

His first 12 first-degree murder charges pertain specifically to murder after deliberation, while the last 12 relate to murder with an “extreme indifference to the value of human life.” In total, the charges work out to two counts for each person who was killed during the July 20 spree.

The same reasoning was used with the 58 people injured. Two counts of attempted murder, after deliberation and with “extreme indifference,” apply to each of the wounded.

Authorities have also laid one charge of possession of explosives against Holmes, whom police allege booby trapped his apartment with trip wires and explosives.

The murder charges both carry a maximum penalty of death. Life sentences handed down for “extreme indifference” convictions are served consecutively.

Tense legal discussions are expected to follow over the sanity of Holmes, a 24-year-old who was in the process of withdrawing from a PhD program in neuroscience.

Colorado law dictates that defendants are not legally liable for their actions if they are too ill to distinguish right from wrong. The law, however, also states that prosecutors must be careful not to confuse mental illness with “moral obliquity, mental depravity, or passion growing out of anger, revenge, hatred, or other motives, and kindred evil conditions."

Authorities allege Holmes started acquiring weapons and gear as early as May and June, months before a masked gunman opened fire during a packed showing of “The Dark Knight Rises.”

Law professor Sam Kamin of the University of Denver said there is evidence that the attack was premeditated, which could complicate possible attempts to use insanity as a defence.

"But," he told The Associated Press, "the things that we don't know are what this case is going to hinge on, and that's his mental state."

It’s possible that Holmes’ public defenders could argue he is not fit to stand trial. Another option, if lawyers fail to convince the court that Holmes is mentally incompetent, lawyers can attempt to avoid a possible death penalty by arguing he is mentally ill.

As well, defence lawyers have filed a motion to find out who told media outlets about a package Holmes allegedly mailed to his psychiatrist at the University of Colorado Denver.

Several media outlets reported that the package, discovered on Holmes’ campus three days after the July 20th shooting, contained a notebook outlining plans to carry out the attack. But Arapahoe Country District Attorney Carol Chambers said in court papers that the package still had not been opened by the time those reports were published.

Court papers confirm Holmes was seeing a psychiatrist at his university but it’s unclear how long he was seeing Dr. Lynne Fenton and for what reason -- mental illness or otherwise.

Craig Silverman, a former chief deputy district attorney in Denver, argues that based on the evidence thus far Holmes’ case appears to be straightforward.

"This is not a whodunit,” he told The Associated Press "The only possible defence is insanity."

During his first court appearance, Holmes appeared with a shock of wavy, red-orange hair, a hairstyle evocative of a hairdo donned by Batman’s rival The Joker.

Onlookers commented that Holmes appeared to be in a daze during the appearance last week.

“What I saw is someone who ultimately stared out into the courtroom as if he was watching a movie,” psychiatrist Mark Goulston told CTV’s Canada AM on Monday.

If Holmes did, in fact, intend to mimic the Joker, Goulston noted that the gesture of modelling one’s self after a villain rather than a hero sends an interesting message.

“It’s unclear what to make of that, except that he identified with the power to do evil as opposed to the power to do good,” Goulston said in an interview from Los Angeles.

Holmes appeared dazed once again during Monday’s court appearance. However, he did confer with one of his lawyers during the proceedings.

Information about Holmes’ case is expected to be strictly controlled. A gag order has been placed on lawyers and law enforcement, his court file has been sealed and his university has been prohibited from releasing records related to Holmes.

While Holmes’ first court appearance was televised, Monday’s was not. District Chief Judge William Sylvester approved a defence request to bar video and still cameras from the courtroom, citing concerns over whether they would compromise Holmes’ right to a fair trial.

Those wounded during the Aurora shooting rampage continue to make a slow march towards recovery, including a young mother who lost her six-year-old daughter during the violence and suffered a miscarriage over the weekend.

With files from The Associated Press