Lawyers for the Colorado cinema massacre suspect have said for the first time that they are considering entering a plea of not guilty by reason of insanity on behalf of their client.
But in court papers made public on Friday, they said they could not make their decision about their defence of James Holmes until the judge ruled on their motion challenging the constitutionality of the state's insanity defence law.
The lawyers 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.
Holmes, 25, is accused of killing 12 people and wounding 70 during a midnight showing of the latest Batman film, The Dark Knight Rises, at the cinema in Aurora, outside Denver, last July. He faces multiple charges of first-degree murder and attempted murder.
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's hearing is on 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 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 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 lawyer and law professor who is also a former prosecutor.
The judge has ordered lawyers not to speak publicly about the case.
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 are 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 affects their decisions about Holmes's defence, his lawyers argue.