CENTENNIAL, Colo.— Prosecutors on Monday said they will seek the death penalty against the man accused in last year’s movie theater attack that killed 12, wounded 70 and spurred new gun control laws in Colorado.

The much-anticipated disclosure came in a court hearing held four days after prosecutors publicly rejected an offer by James Holmes’ attorneys that the former neuroscience graduate student would plead guilty to avoid execution.

Prosecutors had said the defense proposal wasn’t a valid plea bargain offer, although they could still agree to a plea before the case goes to trial.

“It’s my determination and my intention that in this case for James Eagan Holmes justice is death,” Arapahoe County District Attorney George Brauchler said at the Monday hearing. He spoke quietly and deliberately without any hesitation.

There was no audible reaction from Holmes, who sat in court with his back to reporters.

Holmes’ parents sat side by side in the gallery, clutching hands with fingers intertwined.

They were also quiet, as were the victims in the courtroom when Brauchler disclosed his decision, which he said he had shared with no one.

Holmes’ attorneys are expected to argue he is not guilty because he was legally insane at the time of the July 20 shooting. They balked at entering that plea last month, saying they couldn’t make such a move until prosecutors made a formal decision on the death penalty.

Investigators say Holmes methodically stockpiled weapons and ammunition for his assault on a packed midnight screening of “The Dark Knight Rises,” and booby-trapped his apartment to explode and distract any police who responded.

The massacre was repeatedly cited by gun control advocates who pushed a hotly contested package through the Colorado state Legislature last month. The bills include a ban on the sort of high-capacity magazines that Holmes allegedly used to spray the theater with dozens of bullets in a matter of seconds.

President Obama is scheduled to visit Denver on Wednesday to highlight the legislation as part of his push for more gun control following December’s Sandy Hook Elementary School massacre.

As the tangled case against Holmes returns to court, survivors and families of the victims are uncertain about what happens next.

If the case goes to trial, “all of us victims would be dragged along potentially for years,” said Pierce O’Farrill, who was shot three times.

“It could be 10 or 15 years before he’s executed. I would be in my 40s and I’m planning to have a family, and the thought of having to look back and reliving everything at that point in my life, it would be difficult,” he said.

Defense lawyers revealed in a court filing last week that Holmes would plead guilty if prosecutors allowed him to live out his days in prison with no chance of parole instead of having him put to death.

That prompted an angry response from prosecutors, who called it an attempt to gin up public support for a plea deal.

Prosecutors also said the defense has repeatedly refused to give them the information they need to evaluate the plea agreement.

If prosecutors do accept a deal, they will want to ensure that it’s air-tight, said Karen Steinhauser, a former prosecutor who is now an adjunct professor at the University of Denver law school.

Holmes would give up his right to appeal by pleading guilty, she said. And although he could ask to change the plea if new evidence surfaces or if he claimed his lawyers were ineffective, “it’s very, very hard to withdraw it,” she said.

District Judge William Sylvester would want assurances from defense lawyers that Holmes is mentally competent to plead guilty and accept a life sentence with no parole, Steinhauser said.

The judge could order a mental competency evaluation before accepting a guilty plea, but Steinhauser said that’s unlikely unless Holmes showed some sign of incompetence.

She said Sylvester would probably accept the word of Holmes’ lawyers.

If Holmes is convicted and sentenced to prison, the state Department of Corrections would determine what kind of mental health care he gets, said Alison Morgan, a department spokeswoman.

A third of the state’s inmates have moderate to severe mental illness, and the prison system has an extensive mental health division with a 250-bed facility for the acutely mental ill, she said.

Inmates can be sent to the state mental hospital in Pueblo — where people found not guilty by reason of insanity are committed — but the stay is temporary, and they are returned to the prison system after treatment, she said.