CENTENNIAL, Colo.?- Prosecutors in Colorado will seek the death penalty for accused movie theater gunman James Holmes in the 2012 slaying of 12 people during a showing of the Batman film "The Dark Knight Rises", the lead prosecutor said in court on Monday.

Holmes, a 25-year-old former graduate student of neuroscience, is accused of opening fire inside a suburban Denver multiplex during a midnight screening of the movie last July in a rampage that ranked as one of the deadliest mass shootings in the United States.

Accused Aurora theater shooting suspect James Holmes listens at his arraignment in Centennial, Colorado in this file photo taken March 12, 2013. [Photo/Agencies]

It was one of several last year, including the December attack on an elementary school in Newtown, Connecticut, that killed 20 children and six staff members, re-igniting a national debate over gun violence and the limits of the constitutionally protected right to bear firearms.

Holmes is charged with multiple counts of murder and attempted murder in the shooting spree, which also wounded 58 moviegoers. A dozen other people suffered non-gunshot injuries as they fled the Aurora, Colorado, cinema.

At the start of the latest court hearing, George Brauchler, the District Attorney for Araphoe County who is leading the prosecution, formally declared his intention to seek a death sentence should Holmes be convicted.

"My determination for James Eagan Holmes -- justice is death," Brauchler told the judge.

Holmes, bearded with shaggy dark hair, showed no visible emotion as he sat silently at the defense table, shackled and wearing red prison garb and flanked by his lawyers. When he first entered the chamber, the accused glanced briefly at his parents, who were sitting with spectators in the courtroom.

There was an audible gasp from the victims' side of the courtroom, and Holmes parents looked grimly at one another, as Brauchler said he would pursue capital punishment in the case.

A new trial date was set for Feb 3, 2014.

Brauchler had previously announced he had assigned a death-penalty specialist to the prosecution team, and in court documents released March 28 he rejected a suggestion by defense lawyers that Holmes plead guilty in exchange for a life prison term without the possibility of parole.

Last month, Judge William Sylvester entered a not guilty plea on Holmes' behalf, but said he would consider allowing that plea to be changed to not guilty by reason of insanity.

While Holmes' attorneys said in a filing last week they are prepared to mount an insanity defense, they also wrote that their client was "willing to resolve the case to bring the proceedings to a speedy and definite conclusion for all involved" in return for a plea deal that would spare his life.

Brauchler, in a written response, called the defense move improper at this stage of the case, saying, "it was filed for the intended purpose of generating the predictable pretrial publicity."

"The only conclusion that an objective reader would reach ... is that the defendant knows that he is guilty, the defense attorneys know he is guilty and that both of them know that he was not criminally insane," Brauchler wrote.

In court pleadings, public defenders Daniel King and Tamara Brady have said Holmes has been hospitalized twice since his arrest, once for "potential self-inflicted injuries."

At one point, jailers determined Holmes was a danger to himself and in "immediate need of a psychiatric evaluation." He was transported by ambulance to a Denver psychiatric ward "where he was held for several days, frequently in restraints," his lawyers wrote.