Denver: Attorneys for the suspect in a deadly movie theatre shooting said for the first time, in court papers made public Friday, that they are considering entering a plea of not guilty by reason of insanity on behalf of their client.

But they said they can’t make their decision about their defence of James Holmes until the judge rules on their motion challenging the constitutionality of the state’s insanity defence law.

The attorneys say the law is unfair to defendants who invoke it because it requires the disclosure of potentially incriminating information, such as mental health records, while those who plainly plead not guilty are not required to turn over any evidence.

Prosecutors have not announced whether they will pursue the death penalty, but they have 60 days from when a defendant enters a plea to do so. Holmes’ hearing is March 12.

A legal expert said the manoeuvring may be part of a defence strategy to make sure prosecutors never get their hands on a notebook that was purportedly sent by Holmes to his psychiatrist and included descriptions of a possible attack.

The notebook was the subject of court hearings in the months after the July shooting. Under state law, the notebook was protected because it was part of a doctor-patient relationship that Holmes had with the psychiatrist.

“That’s why there’s a big issue there, there’s information that the prosecution may not be entitled to unless they plead not guilty by reason of insanity,” said Karen Steinhauser, a Denver criminal defence attorney and law professor who is a former prosecutor.

Under state law, defendants who plead not guilty by reason of insanity must reveal to prosecutors mental health records as well as psychiatric evaluations that may include details of the crime for which they’re accused.

While the law has not been challenged before in cases involving the death penalty, determining whether it violates a defendant’s constitutional right against self-incrimination directly impacts their decisions about Holmes’ defence, his attorneys argue.

Steinhauser said the defence had to file their motion challenging the insanity defence law before the plea is entered because they could not raise issues with the statute afterward. They could still, however, raise other trial-related issues later.

Steinhauser said the judge can rule on the matter, which likely will be appealed to higher courts and possibly delay Holmes’ arraignment.

Holmes’ attorneys have said their client is mentally ill and had sought the help of a psychiatrist at the University of Colorado, Denver, where he was a neuroscience graduate student.

Holmes faces multiple charges of first-degree murder and attempted murder in the shootings at an Aurora theatre during a midnight showing of the latest Batman movie, “The Dark Knight Rises.”

Holmes was ordered to stand trial following 2 days of testimony from police and federal agents who provided excruciating details about the attack. Holmes had been expected to enter a plea following that hearing, but defence attorneys requested a delay, saying they would not be ready until March.

Legal experts say there may be few options for Holmes. If, as many anticipate, he enters the plea of not guilty by insanity, he would undergo lengthy evaluations at a state psychiatric hospital before trial.

If the case goes to trial and he’s found not guilty by reason of insanity, Holmes could conceivably be released from a psychiatric facility someday if he is deemed to have recovered, but that is considered an unlikely possibility. A guilty plea or conviction could mean life in prison or the death penalty.