Jurors in the Colorado movie theater shooting trial must decide whether James Holmes met the state's legal definition of insanity when he opened fire on a movie theater in the Denver suburb of Aurora.

Prosecutors are seeking the death penalty. Holmes pleaded not guilty by reason of insanity.

His attorneys insist he is mentally ill and was gripped by a psychotic episode at the time of the July 2012 shootings, which killed 12 people and injured 70.

Colorado law defines insanity as the inability to know right from wrong because of a mental illness or defect.

The jury will make that determination based on evidence presented at trial, including two court-ordered evaluations at the Colorado Mental Health Institute at Pueblo that determined Holmes was legally sane.

Two psychiatrists for the defense testified that Holmes did not know right from wrong, and met the legal definition of insanity.

Deciding won't be easy.

"I think that there is no doubt in anyone's mind that this young man was very mentally ill, and all the psychiatrists have agreed to it, and all of the experts have said that but for this mental illness, we wouldn't be here in court today," said Karen Steinhauser, a former prosecutor and adjunct professor at the University of Denver Sturm College of Law. "The issue, and it's really been the issue from the outset of this case, is: Did his mental illness rise to the level of legal insanity? And it's a tough job for the jurors to do."

Scott Robinson, a trial lawyer and legal analyst, said evidence presented at trial might help save Holmes' life if he is convicted.

Testimony from experts for both sides could help the defense in a penalty phase of the trial because they agreed Holmes suffers mental illness.

If Holmes is found not guilty by reason of insanity, he would be committed indefinitely to the state mental hospital and could — at least in theory — be released someday. Experts say that's not likely given the notoriety of the crime.