More than two years after 12 people were killed and 70 others were injured during a movie theater shooting in Aurora, Colo., the trial of the admitted shooter began on Monday.

James Holmes, now 27, is pleading innocence by reason of insanity. His attorneys, both public defenders, have admitted that their client was the gunman during the July 20, 2012, shooting which took place at a Century movie theater during a midnight screen of "The Dark Knight Rises," according to Fox News.

The main argument for the prosecutors is going to be that Holmes was sane enough to plan the attack. Fox News reports that when authorities went to his apartment after the shooting, he had set up traps in preparation of their arrival.

During Monday's opening statements, the prosecution said that Holmes was never able to give a straight answer as to what his motive for the shooting was, according to The Washington Post

District Attorney George Brauchler spoke to the jury about his interactions with Holmes, as reported by The Washington Post:

"Brauchler noted during opening arguments that Holmes told one state expert he decided to carry out the shooting in a movie theater because of the possibility of mass casualties. But Brauchler says Holmes told a defense expert he chose the setting because he liked the movies. When asked about the discrepancy, Holmes allegedly responded 'Things change with time' and offered no other explanation."

The prosecution added that as recent as four months prior to the shooting Holmes was not on medication and "seemed sane." The state also said that medical experts who examined Holmes have not yet been able to come to a decision on what mental disorder he may or may not have.

Prosecutors are seeking the death penalty for Holmes. If the defense of insanity holds up, he would be sent to a mental institution for an unknown amount of time, according to ABC News.

Holmes appeared in court on the opening day of his trial far different than how he looked in 2012, reports ABC News: 

"Holmes, who has previously been seen wearing an orange prison jumpsuit in various court hearings, was wearing khakis, a blue-and-white striped button-down shirt and glasses. Today he also had a small mustache and beard. His new look comes in stark contrast to his earlier appearances, when his unkempt hair was dyed bright orange."