Lois Silver/Reuters

A courtroom sketch shows U.S. Army Staff Sgt. Robert Bales, center, and his defense attorneys Emma Scanlan, second from left, and Maj. Gregory Malson, left, listen to witness Sgt. Jason McLaughlin (R) testify at a U.S. Courts Martial pre-trial proceeding, at Joint Base Lewis-McChord, Washington on Monday. Col. Lee Demecky, top center, is seen presiding over the hearing.

Sgt. Robert Bales, accused of carrying out a massacre of Afghan villagers in March, had been chosen for an especially challenging assignment in southern Afghanistan because he was deemed a top soldier, according to testimony on Wednesday by 1st Sgt. Vernon Bigham, the News Tribune reported.

"We needed to put our best guys" with a Special Forces team at Village Stability Platform Belambay, the Tribune said, quoting Bigham, who testified over a video teleconference link from Kandahar Air Field to the hearings at Joint Base Lewis-McChord, Wash.

Defense attorneys called witnesses Wednesday in hearings that mark the start of the military justice process for Bales, who is accused of slaughtering 16 Afghan villagers, mostly women and children, in a pre-dawn rampage on March 11.

Bales seemed remorseful after he was taken into custody and seemed to want to confess, but Bigham discouraged it, according to the testimony.

"He invoked his rights, so I didn't want him to talk about those things to me," said Bigham.

Bigham's testimony painted a picture of Bales as a capable soldier whom he was trying to groom for a promotion, according the the Tribune. He said that Bales missed the cut for 2011 sergeant first class promotion and was disappointed.

The mission he was on, as part of an attachment to Special Forces across southern Afghanistan, split up the company of men across 14 different sites, limiting normal oversight of the soldiers, he said.

"We gave up control of our guys" to the Special Forces teams, Bigham said.

In testimony later on Wednesday, Special Agent Matthew Hoffman said U.S. Army criminal investigators could not reach the scene of the alleged massacre for three weeks, because American and Afghan leaders considered the area too dangerous.

Focus on Bales' state of mind
The Article 32 hearing at Joint Base Lewis-McChord, Wash., where Bales is based, are to determine whether there is enough evidence to put Bales through a full court martial.

Proceedings started Monday with prosecutors laying out their version of the events. They said the sergeant acted alone and with "chilling premeditation," leaving his base in Kandahar province twice in one night and killing 16 people, mostly women and children in nearby villages as they slept.

Bales faces 16 counts of premeditated murder and six counts of attempted murder, as well as charges of assault and wrongfully possessing and using steroids and alcohol while deployed.

Military prosecutors are seeking the death penalty.

The defense team has not revealed its strategy, but lead civilian defense attorney John Henry Browne has suggested over the past few months that Bales may not have acted alone and may be suffering from post-traumatic stress disorder. Bales was on his fourth combat deployment in 11 years and suffered a concussive head injury in a previous deployment.

Bales has not participated in a medical evaluation known as a "sanity board," because his lawyers have objected to having him meet with Army doctors without them present.

The defendant has appeared in court wearing camouflage fatigues with his head shaved, but has remained silent except to say he understands the charges and his rights. Bales has not entered a plea, and is not expected to testify.

Conflicting accounts
On Tuesday, Bales' defense team began calling witnesses who gave testimony that appeared to cast doubt on the assertion that Bales acted entirely alone.

Testifying Tuesday, Private First Class Derek Guinn said he was told by Afghan guards that two U.S. soldiers were seen entering the compound in the early hours of March 11, and one was seen leaving again.

But Guinn, who spoke to the guards through an interpreter, said he personally did not see anyone leaving or entering Camp Belambay.

His testimony was at odds with the U.S. Army prosecutor's case — supported by several witnesses on Monday — that Bales, 39, left and entered twice on his own, and was solely responsible for the Afghans' deaths.

Witnesses from the Afghan villages where the alleged killing spree took place are set to testify on Friday via video link to the hearings, expected to last two weeks. Some villagers have said that more than one U.S. soldier was present during the attacks.

Guinn's testimony was the first notable discrepancy from the version of events laid out by military prosecutors on Monday.

Covered in blood
In the first session of the hearing, lead prosecutor Lieutenant Colonel Jay Morse said Bales alone was responsible for the deaths, in two premeditated attacks. He showed the court a video taken from a surveillance balloon apparently of Bales returning to the base for a second time, just before 5 a.m.

An Army medic testified on Tuesday that he saw Bales covered in blood and that he knew from experience that the blood was not his own.

The medic, Sgt. First Class James Stillwell, said he asked Bales where the blood came from and where he had been.

Bales responded with a shrug, Stillwell testified, and then said, "If I tell you, you guys will have to testify against me."

The shooting, which if proven at trial would be the worst civilian slaughter by U.S. forces since the Vietnam War, eroded already-strained U.S.-Afghan ties after over a decade of conflict in the country.

NBC News' Kari Huus, The Associated Press and Reuters contributed to this report.

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Updated at 8:50 p.m. ET: Brandon Friedman, an Army combat veteran in Afghanistan and Iraq and author of the highly regarded memoir "The War I Always Wanted," warned against linking post-traumatic stress disorder or conditions at Joint Base Lewis-McChord to Barnes' alleged behavior.

There's "obviously no question of a tie between combat and PTSD," Friedman said in a Twitter message to msnbc.com. "But having PTSD doesn't signify a propensity to murder Americans."

Mount Rainier National Park remains closed until at least Saturday, park officials said.

Barnes was from Riverside County, Calif., and as a teenager attended a community day school for expelled and troubled students, the Press-Enterprise newspaper reported. A young man who answered the door at the family's home said the family had no comment, the paper said.

Original post: The Iraq war veteran believed to have killed a park ranger Sunday was last stationed at a Washington base considered among the military's most troubled facilities, where suicides and violence among service members have reached record levels.

Authorities said they believed Benjamin Colton Barnes, 24 — who was found dead Monday, apparently of hypothermia, in Mount Rainier National Park — shot and killed Park Ranger Margaret Anderson, 34, on Sunday. He is also believed to have shot and wounded four people, two of them critically, earlier in the day at a New Year's party in Skyway, near Seattle, authorities said.

Barnes, a private first class, was discharged from the Army for misconduct in 2009 after he was charged with drunken driving and improperly transporting a privately owned weapon at Joint Base Lewis-McChord, Wash. Lewis-McChord has drawn national attention for widespread problems with post-traumatic stress disorder among service members returning from Afghanistan and from Iraq, where Barnes served in 2007 and 2008.

In July, the mother of Barnes' young daughter said in court papers seeking a protection order that he "has possible PTSD (post-traumatic stress disorder) issues," NBC station KING of Seattle reported. In seeking sole custody of the girl, she said Barnes was suicidal and "gets easily irritated, angry, depressed and frustrated." 

The woman said Barnes had numerous weapons in his home, including firearms and knives, adding: "I am fearful of what Benjamin is capable of with the small arsenal he has in his home and his recent threat of suicide."

A year ago, the military newspaper Star and Stripes rated Lewis-McChord as the most troubled base in the entire U.S. military, with multiple criminal and military investigations under way into troops' behavior and the quality of the medical and mental health care for service members returning from the war.

And that was before the base set a record for presumed suicides in 2011, with 12, according to military statistics scheduled to be released this month but obtained by The Tacoma News-Tribune.

The Army directed base officials last year to focus specifically on the mental health of members of the 5th Stryker Brigade, which saw heavy action in Afghanistan in 2009 and 2010. Barnes served with a Lewis-McChord Stryker brigade, although officials said they didn't immediately know whether it was the 5th.

The problem isn't confined to Lewis-McChord. In a paper for the Army War College last year (.pdf), Army Col. Ricardo M. Love reported that "veterans returning from Iraq and Afghanistan are diagnosed with Post-Traumatic Stress Disorder (PTSD) at an alarming rate."

A 2008 RAND Corp. study indicated that 18 percent of all service members returning from Iraq and Afghanistan since 2001 had "PTSD or major depression." Only about half seek treatment, it said.

"Although Commanders are conducting tough and realistic training prior to deployment, the high number of returnees diagnosed with PTSD indicates we are not doing enough," Love concluded.

But the problem is especially severe at Lewis-McChord, which the Los Angeles Times profiled as "a base on the brink" just last week.

"I can tell you that in the last two years, we have had 24 instances in which we contacted soldiers who were armed with weapons," Bret Farrar, police chief in nearby Lakewood, told the newspaper. "We've had intimidation, stalking with a weapon, aggravated assault, domestic violence, drive-bys."

The issues have come to widespread public attention after Lewis-McChord's heaviest year of deployments in Iraq and Afghanistan, where 18,000 soldiers from the base served in 2009-10.

The base, near Tacoma about 50 miles south of Seattle, has seen numerous violent incidents, leading to several charges and convictions of soldiers for serious crimes. According to The Seattle Times, they include:

• Pfc. Dakota Wolf, 19, who is charged in the stabbing death Nov. 30 of a 19-year-old woman in a Seattle suburb while AWOL.
• Sgt. David Stewart, 38, who killed himself and his wife after leading authorities on a high-speed chase in April. Their 5-year-old son was found dead at home.
• Spc. Ivette Gonzalez Davis, 24, who was sentenced to life in prison in August 2010 for shooting two soldiers and kidnapping their baby.
• Sgt. Sheldon Plummer, who was sentenced to 14 years in prison for strangling his wife in February 2010.

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