Less than two weeks before Staff Sgt. Robert Bales faces a sentencing hearing for the murder of 16 Afghan civilians, his attorneys want Army prosecutors removed from the case.

Defense attorneys made the request because prosecutors inadvertently received an unredacted copy of a sanity-board report that evaluated Bales’ mental health, according to John Henry Browne, Bales’ Seattle attorney.

A hearing on the motion is next Tuesday at Joint Base Lewis-McChord, according to Browne. The full report would give prosecutors an unfair advantage as they make their arguments in the final phase of the court-martial scheduled to begin Aug. 19, he said.

“They are not supposed to get it; this was a serious mistake,” Browne said.

During the sentencing phase, an Army panel will decide whether Bales, a soldier from JBLM, will spend the rest of his life in prison or eventually be eligible for parole.

Military sanity boards are composed of doctors who meet with defendants to review their files to understand more about their personal life and military experiences. The boards are charged with determining whether the accused had a severe mental disorder or defect at the time of alleged crimes, and is able to appreciate the wrongfulness of the alleged conduct and understand the court-martial proceedings.

The board that examined Bales produced a brief document stating he was fit to stand trial, and a longer report that Browne said should not have been shared with prosecutors before the sentencing hearing.

Browne said an Army judge inadvertently passed on the unredacted, longer copy to the prosecutors.

The defense team wants new prosecutors appointed to argue the Army’s case at the sentencing. If the motion is granted, the sentencing hearing could be postponed for weeks or months, according to Browne.

But the judge also could rule to retain the current prosecutors, said Dan Conway, who has represented numerous military defendants including a JBLM soldier accused of murder in Afghanistan.

“There could be less extreme options that would place limitations on the prosecutors’ ability to use the evidence,” Conway said.

Bales pleaded guilty in June to the murder of the 16 Afghan civilians while serving in Afghanistan in March 2012. That plea was part of an agreement reached with prosecutors that removed the possibility of a death sentence.

Bales’ actions represent the worst U.S. war crime to be prosecuted from the Afghanistan conflict.

Early on March 11, 2012, Bales twice left his small outpost in Kandahar province to murder civilians, most of whom were women and children. He burned some of the bodies before returning to his outpost in a blue cape wrapped around bloodstained clothes.

“As far as why, I have asked that question a million times since then, and there is not a good reason in this world for why I did the horrible things that I did,” Bales said at the June hearing.

At the sentencing hearing, Bales’ attorneys are expected to cite a range of extenuating circumstances to marshal the argument that their client, who was on his fourth tour of duty to a combat zone, should be allowed eventually to apply for parole.

Hal Bernton: 206-464-2581 or hbernton@seattletimes.com