In documents released Tuesday, defense lawyers confirmed they filed the appeal and asked that the document remain out of the public's view.
James Holmes pleaded not guilty by reason of insanity to charges of killing 12 people and injuring 70 in the 2012 attack. He underwent a mandatory sanity evaluation last summer, but the judge ordered another exam after prosecutors complained that the doctor who conducted the first one was biased.
Defense lawyers asked both the Supreme Court and the presiding judge to keep the appeal sealed. Neither court has responded, but the appeal remains sealed for now.