By Keith Coffman
DENVER (Reuters) - Accused Colorado theater gunman James Holmes, who could face execution if convicted of murdering 12 moviegoers last year, returns to a Colorado courtroom on Monday where his lawyers will seek to change his plea to not guilty by reason of insanity.
Holmes, 25, is charged with multiple counts of first-degree murder and attempted murder for opening fire during a midnight screening of the Batman film "The Dark Knight Rises" last July.
The attack, which along with last year's Connecticut school rampage helped reignite a national debate on gun control, ranks as one of the nation's deadliest mass shootings. Fifty-eight people were also wounded by gunfire.
A court filing by Holmes' public defenders last week said he intended to enter the plea at a hearing on May 13, but the lawyers continued to object to the constitutionality of the state's insanity defense law.
A judge had previously entered a not guilty plea for the former neuroscience graduate student in March, but ruled that it could be changed to not guilty by reason of insanity if defense lawyers showed "good cause."
Prosecutors announced last month that they would seek to put the California native to death if he is convicted of the massacre, citing the "especially heinous, cruel or depraved" nature of the crime.
Since it is a death penalty case, it is widely expected that Arapahoe County District Judge Carlos Samour Jr. will grant the change-of-plea request.
Defense lawyers hinted in an earlier pleading that they may enter the insanity plea over their client's objections. If an insanity defense is raised, Colorado law requires that the prosecution must prove a defendant was not insane at the time of the alleged crime.
Holmes' public defenders have said in written filings and in open court that their client suffers from an unspecified mental illness.
Twice since his arrest, Holmes has been transported from his jail cell to a hospital, once where he was held for several days in a psychiatric ward "frequently in restraints," his lawyers said in a court filing.
Police said they found inside Holmes' apartment a bottle of the anti-seizure medication clonazepam, which can also be used to treat anxiety disorders, and a bottle of the anti-depressant sertraline, known by its brand name Zoloft.
It is unclear if Holmes had either drug in his system when he was arrested after the shooting spree.
At a preliminary hearing in January, prosecutors laid out their case against Holmes, with investigators detailing his weapons purchases, the rigging of his apartment with explosives, along with other plans to commit mass murder.
Also at issue at Monday's hearing is a defense motion asking the judge to apply "heightened standards or fairness and reliability" for all proceedings in the capital case to ensure that Holmes is accorded due process.
Prosecutors responded in a written motion that the defense motion is vague and "essentially meaningless" because case law supports the elevated threshold only in the sentencing phase of death penalty cases, not at the trial level.
"Defendants in noncapital case and capital cases are entitled to the same constitutional rights during the trial on the underlying offense," the prosecution motion said.
Holmes' trial is scheduled for February 2014.
(Editing by Tim Gaynor and Eric Walsh)