The judge in the deadly Colorado movie theater shooting case entered a not guilty plea on behalf of James Holmes on Tuesday after the former graduate student's defense team said he was not ready to enter one.

If Holmes is convicted, he could be executed or spend the rest of his life in prison. Judge William Sylvester said Holmes, 25, can change his plea to not guilty by reason of insanity later, if he chooses.

Such a change could be the only way Holmes could avoid life in prison or execution. Prosecutors have not said yet whether they will pursue the death penalty, announcing Tuesday that they will make their decision known on April 1.

Holmes is charged with 166 counts, mostly murder and attempted murder, in the July 20 attack on moviegoers at a midnight showing of “The Dark Knight Rises'' in the Denver suburb of Aurora that killed 12 people and injured 70. The brutal killings were one of a string of public mass killings last year that launched a fierce national debate over gun control.

The judge set Aug. 5 for the start of the trial. Prosecutors and defense attorneys declined comment.

As he has done in past hearings, Holmes sat silently through Tuesday's proceedings. He wore a red jail jumpsuit and sported a thick, bushy beard and unkempt dark brown hair.

When he walked into the courtroom, he looked at his parents, James and Arlene Holmes. They sat silently at the front of the room and left without comment after the hearing.

In the nearly eight months since Holmes first shuffled into court with vacant eyes and reddish-orange hair, neither he nor his lawyers have said much about how he would plead.

Holmes' lawyers repeatedly raised questions about his mental health, including a recent revelation that he was held in a psychiatric ward for several days last fall, often in restraints, because he was considered a danger to himself.

That raised the possibility that they could end up entering a plea of not guilty by reason of insanity at the hearing Tuesday. Holmes' lawyers, however, said they were not ready to enter a plea.

A not guilty by reason of insanity plea carries risk. Prosecutors would gain access to Holmes' mental health records, which could help their case if the evidence of insanity is weak.

If Holmes does plead insanity, the proceedings would be prolonged further while he is evaluated by state mental health officials. With the judge entering the plea, prosecutors still don't have access to Holmes' health records.

During Tuesday's hearing, defense attorney Daniel King said he could not advise Holmes on what plea to enter. He said the defense wasn't ready despite previous delays _ prompting prosecutors to object.

Sylvester asked King when Holmes might be ready to enter a plea.

“We could be ready by May 1. It may be June 1,'' King said.

“So how am I supposed to make an informed decision?'' Sylvester asked before entering the not guilty plea. He said the defense can always petition to change the plea to not guilty by reason of insanity.

If a jury agrees he was insane, Holmes would be committed indefinitely to a state mental hospital. There would be a remote and unlikely chance he could be freed one day if doctors find his sanity has been restored.

Prosecutors laid out a case that Holmes methodically planned the shooting for months, amassing an arsenal and elaborately booby-trapping his apartment to kill anyone who tried to enter.

On the night of the attack, they say, he donned a police-style helmet, gas mask and body armor, tossed a gas canister into the seats and then opened fire.

Some of the victims and their families said they were grateful the judge is moving proceedings along.

“I was glad the judge was able to enter a plea so we could get the clock ticking,'' said Jessica Watts, whose cousin Jonathan Blunk was killed.

Marcus Weaver, who lost his friend Rebecca Wingo and was shot in the arm at the theater, said the district attorney's office has been surveying families about whether Holmes should face the death penalty.

He said that based on conversations he's had with other victims “the death penalty does seem to be what everyone feels like.''

Weaver said he thinks the death penalty should be pursued if Holmes fights the accusations but not if he pleads guilty.

Also the week of April 1, the judge will hold a hearing on who leaked information about a notebook that Holmes sent to a psychiatrist before the shooting, violating a gag order. King said Tuesday that a judge in New York has signed a subpoena for Fox News reporter Jana Winter to testify about her story, which cited unidentified law enforcement officials.

Holmes' attorneys are trying to get Winter to disclose her sources for the story. Her lawyer has said that shield laws in New York and Colorado protect Winter from demands to reveal her sources. (AP)