A Colarado judge in the Aurora theater massacre ruled Monday that James Holmes can plead not guilty by reason of insanity.
Judge Carlos Samour Jr said his decision was “consistent with fairness and justice” for Holmes, the LA Times reported.
It followed a submission Monday from defense attorney Daniel King who told the court medical experts had made a diagnosis and had a "qualified opinion" on Holmes' mental state which would support the plea.
He did not disclose to the court what the diagnosis was or who had made conducted the examination.
Holmes' attorneys announced last week they wanted to change his plea to not guilty by reason of insanity, CNN reported.
Under Colorado law an accused can change a plea to not guilty by reason of insanity if there is a compelling reason.
Holmes is charged with opening fire on a crowd of people at an Aurora theater last July, killing 12 people and injuring 70.
"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, ABC reported.
The judge however did not formally accept the plea, saying he would delay his decision until later this month.
AP reported that 18 of the victims and family members of the victims had formally objected to his insanity plea.
A trial is scheduled to begin February 2014 and is likely to last for at least four months.
If convicted, Holmes faces the death penalty.