Lawyers for James Holmes, the 25-year-old man accused of opening fire in a crowded movie theater in Aurora, CO and as a result killing 12 people and injuring many more, say they intend to pursue an insanity defense at his trial.

Holmes is accused of entering a movie theater in Aurora, CO in July 2012 during a midnight screening of the Batman movie "The Dark Knight Rises" and shooting at the audience, killing 12 moviegoers and injuring 60 more. He is facing 160 counts, including murder and attempted murder.

In a court document filed Tuesday it is stated that "Mr. Holmes intends to tender a plea of not guilty by reason of insanity." Holmes's attorneys have said that they intend to request a change of plea from the standard not guilty plea that has already been entered at a hearing scheduled for Monday May 13th.

Presiding at Monday's hearing, Judge Carlos Samour Jr. wrote in an order that he will allow Holmes's legal team to argue that they have "good cause" for the plea change, The Denver Post reports.

"After the court determines whether 'good cause' exists, it will decide how to proceed," Samour said in his order.

It's not unexpected that Holmes would eventually opt for a plea of insanity for his alleged crimes, as his lawyers repeatedly reported that the man is mentally ill in previous court proceedings. Holmes had been seeing a psychiatrist prior to his brutal massacre. An insanity plea would break any confidentiality agreement between his himself and his doctor, who would likely testify during the trial.

If Samour agrees to the new plea Holmes will likely be transferred from prison to a psychiatric hospital where he would undergo a comprehensive evaluation by Colorado state psychiatrists. This process could be a considerably lengthy one and officials say they expect it would push back the start date of the trial, which is currently slated to begin in February of 2014. Additionally, as a result of the psychiatric evaluation the case could end up lasting for a substantially longer amount of time than was originally anticipated, according to reports.

"We know it's going to be a lengthy process," Tom Sullivan, whose son was killed during the shooting, told ABC News. "We're resigned to whatever it takes. This is the guy who did it. He'll never see freedom again."