Hearing may be 'mini-trial' in Colorado movie theater shootings

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.