James Holmes Asks to Plead Insanity
PHOTO: James Holmes sits in the courtroom during his arraignment in Centennial, Colo. on March 12, 2013.

Attorneys for accused Aurora theater shooter James Holmes say mental health experts have now examined and diagnosed their client, prompting them to ask a judge today to change Holmes' plea to not guilty by reason of insanity.

"We now have a diagnosis that is complete," defense attorney Daniel King told the judge.

King did not reveal what the diagnosis is, but told the judge they were now ready to enter an insanity plea. In March, a judge entered a standard not guilty plea on Holmes' behalf over the objection of defense attorneys who said they needed more time before entering a plea.

Holmes is accused of opening fire last July 20 during a midnight screening of "The Dark Knight Rises" Batman movie, killing 12 people and injuring another 70. He faces a total of 166 counts, including murder and attempted murder.

If tried and convicted of the murders, Holmes could face the death penalty.

This is the first official plea from Holmes' attorneys.

Judge Carlos Samour did not immediately rule on whether he would accept the new plea, but signaled he is leaning in Holmes' favor. Under Colorado law, a plea can be changed after an arraignment if attorneys show "good cause." Samour said Holmes' defense team had met that burden.

"Allowing Mr. Holmes to enter a plea of not guilty by reason of insanity would be consistent with fairness and justice," Samour told a packed courtroom.

Samour said he would rule on whether to accept the new plea later this month.

Holmes appeared in a maroon jail jumpsuit, but showed little reaction to the proceeding. He has grown a full beard and sideburns, his brown hair slightly disheveled. Eight armed court deputies were positioned around him in the courtroom. He did not speak during the proceeding.

Holmes' physical appearance has evolved over his time in prison, visible only in rare court appearances. He has gone from wild, Joker-like orange and red hair in his first appearance to his most recent look of brown hair and a shaggy beard. He has sometimes looked bug-eyed and confused and other times so despondent and drowsy that people questioned whether he had been drugged.

Prosecutors objected to Holmes changing his plea, arguing that defense attorneys had dragged their feet.

"Our largest frustration is the amount of time it has taken to get to this point," said senior deputy district attorney Jacob Edson.

King countered that the case is complex and voluminous, and that the defense team has been working "on all cylinders" in preparing to enter a plea.

"Mr. Holmes mental illness hasn't changed in the last 60 days," King told the judge. "We acted as promptly as we could."

More ABC News