By Jessica Mintz
TACOMA, Wash (Reuters) - A U.S. Army sergeant is due to go on trial on Friday charged with murdering unarmed civilians and taking body parts for war trophies as ringleader of a rogue platoon that terrorized villagers in Afghanistan.
The court-martial of Staff Sergeant Calvin Gibbs, 26, marks the climax of an 18-month investigation of the most egregious case of atrocities U.S. military personnel are accused of committing during a decade of war in Afghanistan.
Pentagon officials have said the misconduct exposed by the case, which began as a probe into hashish use within Gibbs' unit, had damaged America's image around the globe.
Published photographs showing two fellow soldiers posing with the bloodied corpse of an Afghan boy they had just killed have drawn comparisons to the inflammatory Abu Ghraib prisoner abuse scandal in Iraq in 2004.
Gibbs, from Billings, Montana, is charged with three counts of premeditated murder, as well as cutting fingers off dead bodies and beating a fellow soldier who had alerted superiors to widespread drug abuse within their unit.
Charging documents said he was found in possession of "finger bones, leg bones and a tooth taken from Afghan corpses."
If convicted of all charges, Gibbs faces a maximum sentence of life in prison without the possibility of parole.
Prosecutors have cast him as the chief instigator among five infantrymen from the 5th Stryker Brigade accused of slaying civilians in random killings staged to look like legitimate combat casualties in Kandahar province.
Seven others soldiers were charged with various lesser offenses, ranging from assault for opening fire at civilians to using illegal drugs. Most have already reached plea deals.
About 30 witnesses are expected to testify during the court-martial, slated to run through next week at Joint Base Lewis-McChord near Tacoma, Washington, according to Army spokesman Major Christopher Ophardt.
The first day of proceedings will likely be devoted to selecting a jury panel and handling procedural motions.
(Writing by Steve Gorman; Editing by Jerry Norton and Paul Simao)