Judge enters not guilty plea for Colorado shooting suspect James Holmes

[Updated at 11:18 a.m. MT]

CENTENNIAL, Colo.— In somewhat of an unexpected twist, James Holmes declined to enter a plea during his arraignment Tuesday morning, so the judge made a plea of not guilty on his behalf.

But Judge William Sylvester left the door open for Holmes to change the plea to not guilty by reason of insanity at a later date.

The former neuroscience student was arraigned Tuesday in a crowded Arapahoe County courtroom. Holmes' public defenders told the court that they were not prepared to make a plea because they still had mental evaluations and other work to do.

"At some point this case has to move forward," prosecutor Karen Pearson argued. "That's what the victims wish in this case."

Holmes’ parents, Robert and Arlene, sat together in the second row of the packed courtroom, just several feet from their son, who wore a red jail jumpsuit and now has longer, bushier brown hair and a thick beard. They left the courtroom with tears in their eyes after the 30-minute proceeding.

Daniel King, Holmes' lead attorney, said part of the delay on entering a plea is not knowing if his client could face execution. It puts them in a "Catch-22" with how to proceed, he said. When King told Sylvester the defense team wasn’t ready to plead, several victims and their families near the back of the courtroom dropped their heads. One groaned, seemingly in disgust.

Sylvester asked King how much time the defense needed.

“[That’s] very difficult to say, judge. We could be ready by May 1. I don’t know,” King responded. “It may be June 1. It’s very difficult for us to predict. I wish I could give the court a better answer.”

Pearson told Sylvester she found King’s reasoning “disingenuous,” saying the defense had received information it had asked of the court, but it was now saying it wasn’t prepared. At that point, a seemingly irritated Sylvester ruled he would enter the not-guilty plea on Holmes’ behalf.

The district attorney's office said it will announce on April 1 if it plans to seek the death penalty. Sylvester scheduled the trial to begin in August for four weeks.

Prosecutors allege that Holmes was the gunman who opened fire last July inside a packed premiere of “The Dark Knight Rises” Batman movie in the Denver suburb of Aurora. Twelve people were killed and 70 others wounded (either by gunfire or during the melee to get out).

The 25-year-old faces multiple counts of murder and attempted murder.

Holmes was arrested behind the theater minutes after the massacre. He was clad in combat gear and had weapons nearby.

[RELATED: 'Truth serum' may be used to assess Holmes' sanity]

His court-appointed defense attorneys have said Holmes is mentally ill.

In a notice posted to the court's website on Monday, Judge William Sylvester advised Holmes that the legal definition of insanity applies to someone "who is so diseased or defective in mind at the time of the commission of the act as to be incapable of distinguishing right from wrong with respect to that act."

However, Sylvester also noted, an insane person should not be confused with someone who has "moral obliquity, mental depravity, or passion growing out of anger, revenge, hatred, or other motives and kindred evil conditions."

At the conclusion of a preliminary hearing in January, prosecutors declared they had presented overwhelming evidence that Holmes meticulously planned and executed the attack without remorse.

"Because he wanted to kill all of them, and he knew what he was doing," prosecutor Karen Pearson said.

Whether Holmes is diseased or defective in mind (as the defense has implied it will argue) or is a mass murderer fueled by anger and bent on revenge (as the prosecution has alleged) is central to the case.

Holmes' mental state has been the crux of his attorneys' arguments. Starting with his first court appearance in July and in numerous hearings since, they devoted the bulk of their arguments to his relationship with his university psychiatrist, a notebook he sent her shortly before the shooting and when Holmes' treatment with his psychiatrist ended. Those details, they said, only began to examine the depths of Holmes' mental illness.

[RELATED: Senators seek tougher gun background checks for mentally ill]

The prosecution, meanwhile, has repeatedly sought information apparently unrelated to Holmes' mental state—his grades, school emails, admission applications, his purchases of ammunition, gas masks, grenades and body armor—to show that Holmes concocted what they call a "detailed and complex" plan to slaughter movie patrons at the Aurora multiplex, just east of Denver.

Yahoo reporter Jason Sickles contributed to this report.