Lawyers for Colorado theater shooting suspect James Holmes have for the first time confirmed they are considering entering a plea of not guilty by reason of insanity on behalf of their client.

But they say in a motion made public Friday that Holmes shouldn’t have to enter a plea until the judge rules on whether Colorado’s insanity law is unconstitutional.

They say the law is unfair to defendants who invoke it because it requires the disclosure of potentially incriminating mental health records, while those who simply plead not guilty are not required to turn over evidence.

The 25-year-old Holmes is charged with going on a rampage in July at a suburban Denver movie theater that killed 12 people and injured 70. Holmes is scheduled to enter a plea March 12.