In motions released Monday, the district attorney's office asked the judge to bar testimony about how the state puts inmates to death if the trial gets to the sentencing phase.
Holmes is accused of opening fire in a theater full of people watching a Batman movie in suburban Denver in July 2012, killing 12 and wounding 70. He pleaded not guilty by reason of insanity to multiple charges of murder and attempted murder.
His trial is scheduled to start Feb. 3 with jury selection.
Prosecutors are seeking the death penalty. Under Colorado law, that means if the jury convicts Holmes of first-degree murder, the same jury decides whether he should be executed or sentenced to life without the possibility of parole.
Colorado uses lethal injection for executions, but questions have been raised about whether the chemicals prescribed by law are available.
Further clouding the picture, Gov. John Hickenlooper stepped into another death penalty case in May, indefinitely delaying the execution of a prisoner already on death row because of questions about the fairness of the state's death penalty system and about the availability of the drugs.
The prosecution motion, one of several filed Friday and made public Monday, appears to be a pre-emptive move to keep those questions from creeping into Holmes' trial.
Other prosecution motions asked the judge to bar testimony during the sentencing phase about how Holmes' family and friends would be affected if he is executed, and what prison is like for inmates serving life without parole—apparently hoping to keep the defense from trying to convince jurors that prison would be harsh for Holmes and they wouldn't be letting him off easy if they send him there.
Prosecutors also asked the judge to bar the defense from trying to raise doubts in jurors' minds during the sentencing phase about whether Holmes should have been convicted.
Also Monday, a judge ordered Fox News reporter Jana Winter to return to court Sept. 30 for possible questioning about her confidential sources for a story about Holmes.
Holmes' attorneys want to know who told Winter that before the shootings, Holmes sent a psychiatrist a notebook containing violent drawings.
Defense lawyers contend that the leak violated a gag order. They also say police officers may have undermined their credibility as witnesses if they lied when they denied being Winter's source.
Winter has said she won't identify her sources. That could result in a jail sentence for contempt of court if the judge decides her testimony would be relevant.
Winter, who is based in New York, is awaiting a decision by a New York state appeals court challenging a lower court judge's decision to enforce the Colorado subpoena. If she wins the appeal, the subpoena would have no force and she wouldn't have to testify.
Holmes was not in court Monday. Authorities won't say whether he is at the state mental health hospital in Pueblo undergoing a mandatory sanity evaluation.
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