Updated

A U.S. soldier charged with killing 16 Afghan civilians is expected to undergo a court-ordered review of his sanity beginning this weekend.

The review of Staff Sgt. Robert Bales by Army doctors will start Sunday and could last three to seven days, his attorney John Henry Browne said Wednesday.

Bales is accused of murdering Afghan villagers, mostly women and children, during pre-dawn raids on March 11, 2011. Bales, who was on his fourth combat deployment, slipped away from his base in southern Afghanistan to attack two nearby villages and returned soaked in blood, prosecutors say.

He has not entered a plea. The Army is seeking the death penalty.

Browne previously objected to the sanity review because the Army would not allow the proceedings to be recorded, would not let Bales have a lawyer present, and would not agree to appoint a neuropsychologist expert in traumatic brain injuries to be involved.'

However, a military judge ruled in January that Bales must participate, and Browne said continuing to refuse could preclude the defense from introducing mental health issues at his court martial, scheduled for September at Joint Base Lewis-McChord south of Seattle.

"We're concerned that if we don't, we might be cut off on the mental health issues," he said.

Browne said he is still hoping the Army will allow the proceedings to be recorded or attended by a defense lawyer.

Such reviews are aimed at discerning a defendant's mental state at the time of the crime and their competency to stand trial.

Last week, six Afghan civilians who are expected to testify at Bales' trial traveled to Lewis-McChord. The purpose of the trip was to familiarize them with the process and logistics for the court martial, said Lt. Col. Gary Dangerfield, an Army spokesman at the base.

Among the visitors was Haji Mohammad Naim, who was shot and wounded during the massacre, said Lela Ahmadzai, an Afghan filmmaker who said she spoke with relatives of the victims recently.

Ahmadzai, who lives in Germany, marked this week's anniversary of the killings by releasing a web documentary about the attack, "Silent Night: The Kandahar Massacre", including dramatic interviews with some of the victims recorded in October.

"It's really hard to hear about it from the kids' perspective," she said. "I wanted to show them, to give them a space to talk. They don't usually get that."