James Holmes, theater shooting suspect, faces formal charges Monday

DENVER -- Colorado prosecutors are expected to file formal charges against James Eagan Holmes, the former neuroscience student accused of killing 12 people and wounding 58 others at an Aurora movie theater.

Cameras will not be allowed in the courtroom during Monday morning's hearing where attorneys will also argue over a defense motion to find out who leaked information to the news media. The information included details about a package the 24-year-old former neuroscience graduate student allegedly sent to his psychiatrist at the University of Colorado Denver.

Authorities seized the package July 23, three days after the shooting, after finding it in the mailroom of the medical campus where Holmes studied. Several media outlets reported that it contained a notebook with descriptions of an attack, but Arapahoe County District Attorney Carol Chambers said in court papers that the parcel hadn't been opened by the time the "inaccurate" news reports appeared.

Both Aurora police and CU were not able to comment on the notebook citing a court imposed gag-order forbidding them from discussing any details of the investigation.

Legal analysts expect the case will be dominated by arguments over the defendant's sanity.

Holmes allegedly began stockpiling gear for his assault four months ago, well before the shooting spree just after midnight during a showing of the Batman film "The Dark Knight Rises." He was arrested by police outside the theater.

Police believe the attack was meticulously planned. Holmes had four guns with him during the shooting and had bought hundreds of rounds of ammunition, police have said.

Analysts say that means it's likely there's only 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."

Experts say there are two levels of insanity defenses. Holmes' public defenders could argue he is not mentally competent to stand trial, like Jared Loughner, who killed six people when he shot Arizona Rep. Gabrielle Giffords in Tucson in 2011. Loughner has pleaded not guilty to charges in the shooting. He has been diagnosed with schizophrenia and is undergoing treatment at a Missouri prison facility in a bid to make him mentally fit to stand trial.

If Holmes' attorneys cannot convince the court that he is mentally incompetent, and he is convicted, they 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.

Holmes was not expected to enter pleas on Monday.

Holmes ultimately could enter a plea to the anticipated dozen first-degree murder charges verbally, or his attorneys could enter it for him. Prosecutors may file multiple counts of attempted first-degree murder and other charges against Holmes, whom Aurora police say booby-trapped his apartment with the intent to kill any officers responding there the night of the theater attack.