The man accused in the deadly Colorado theater shootings wants to change his plea to not guilty by reason of insanity, his lawyers said Tuesday, despite their fears that the plea could severely hamper his ability mount a defense against the death penalty.

James Holmes is charged with more than 160 counts of murder and attempted murder in the July 20 assault on a packed movie theater that killed 12 and injured 70. Prosecutors announced last month they would seek the death penalty.

Holmes was widely expected to plead insanity given the compelling evidence against him, but his attorneys put it off for weeks, saying state laws on the death penalty and insanity overlap in ways that violate his constitutional rights and his ability to mount an effective defense.

One of their worries: If Holmes doesn't cooperate with doctors who will evaluate his sanity at the state mental hospital, he could be barred from calling witnesses to testify about his mental condition during sentencing. That would make it nearly impossible for his lawyers to use his mental state as an argument against the death penalty.

“If you don't cooperate during the evaluation phase, you lose the right to call witnesses in your own behalf who could help convince a jury that your life should be spared,” said Karen Steinhauser, an adjunct law professor and former prosecutor.

Two judges previously refused to address the constitutionality question, saying Holmes couldn't challenge the insanity law unless he entered an insanity plea first. That gave his lawyers little choice but to enter the plea and then try to make their case against the law.

Their filing Tuesday made it clear they are not giving up their right to challenge the laws, Steinhauser said.

Holmes was supposed to enter a plea March 12, but his lawyers said he refused to do so because the constitutional questions prevented them from giving him good advice. The judge in charge at the time, William Sylvester, entered a standard not guilty plea for him.

Sylvester withdrew from the case April 1, saying his administrative duties as chief judge of the district wouldn't allow him enough time. Sylvester assigned District Judge Carlos Samour to take over.

Samour must approve the new plea before Holmes is allowed to enter it, and he already has said he would require an explanation before he does so. Steinhauser said she doesn't think that will be an issue.

If the judge does accept the plea, Holmes would be sent to the state mental hospital, where doctors would determine whether he was sane at the time of the shootings. If the doctors do determine Holmes was insane, a jury could still find him guilty.

Prosecutors declined to comment.

Colorado law defines insanity as the inability to distinguish right from wrong, caused by a diseased or defective mind. The law specifically excludes depravity, “moral obliquity” and passion caused by anger, hatred or other emotions from being considered insanity.

Prosecutors say Holmes, 25, spent months buying guns and thousands of rounds of ammunition, donned police-style body armor and opened fire during a midnight screening of the latest Batman movie. (AP)