The judge in the case of Colorado shooting suspect James Holmes has delayed the trial until next February and has acknowledged even that date might be pushed back.

The trial had been proposed for August.

However, all sides agreed Monday the case will take longer now that prosecutors say they'll seek the death penalty.

Prosecutors want the case wrapped up by spring of next year. But defence lawyers say there's no way that can happen.

Defence lawyer Tamara Brady says the lawyers will do whatever it takes to defend Holmes' life and don't want the trial rushed.

The 25-year-old man accused of killing 12 people in a movie theatre in Aurora, Colo., last year will face possible execution if convicted, prosecutors announced on Monday.

The announcement came after behind-the-scenes manoeuvring erupted into a public quarrel between prosecutors and the defence over Holmes' public offer to plead guilty in exchange for spending the rest of his life in prison.

As the case returned to court, survivors and families of the victims expressed concerns over having a 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.

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Arlene and Robert Holmes, parents of accused Aurora theatre gunman James Holmes, leave their son's arraignment in Centennial, Colorado on March 12, 2013. (Rick Wilking/Reuters)

Holmes is accused of meticulously planning and brutally executing a plan to attack a Colorado movie theatre at midnight during a showing of the latest Batman movie, killing 12 people and injuring 70.

Defence 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 rejected the offer four days ago and called it an attempt to gain public support for a plea deal.

Prosecutors also said the defence has repeatedly refused to give them the information they need to evaluate the plea agreement. Although they argued the defence proposal wasn't a valid plea bargain offer, they could still agree to a plea before the case goes to trial.

Holmes' lawyers 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 theatre with dozens of bullets in a matter of seconds.

Obama to visit Denver on Wednesday

U.S. President Barack 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 in Connecticut.

Holmes would give up his right to appeal by pleading guilty, said Karen Steinhauser, a former prosecutor who is now an adjunct professor at the University of Denver law school.

And although Holmes 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 defence 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.