Holmes' attorney told the court that he was not ready to enter a plea, but the judge entered a not guilty plea for him and said he could change the plea to not guilty by reason of insanity, reports the Associated Press.
Holmes sat silent, but alert, throughout the hearing, alternately appearing to look at the judge and stare into space.
Holmes, who is facing 166 counts, mostly of murder and manslaughter, has spent the past eight months behind bars. He was reportedly restrained in a psychiatric ward for several days during the fall out of fear he might harm himself.
To be found not guilty by reason of insanity, Holmes has to prove that he did not know right from wrong when he committed the crime of which he is accused. Prosecutors say Holmes planned the massacre well in advance, ordering arms and ammunition through the internet and dressing in paramilitary gear on the night of the assault. Police also found explosives in his apartment that had reportedly been rigged to go off when authorities entered.
In many ways, Holmes is an anomaly. He had no known connection to any of his victims, and unlike Newtown shooter, or Columbine shooters Eric Harris and Dylan Klebold, he did not end his massacre by committing suicide.
Some parallels can be drawn between Holmes and, the man who opened fire outside a Tucson supermarket in January 2011, killing 6 and wounding 13 others, including former Congresswoman Gabrielle Giffords. Loughner, a diagnosed schizophrenic, was initially ruled not competent to stand trial, but after more than a year of treatment inside a federal prison, pleaded guilty to the charges against him and was sentenced to life without parole.
The District Attorney will make an announcement on April 1 about whether he intends to seek the death penalty for Holmes. Holmes' defense attorney asked for more time to prepare.Complete coverage of James Holmes on Crimesider