Joint Base Lewis-McChord, Washington (CNN) -- It didn't take long for Staff Sgt. Calvin Gibbs to make an impression on his soldiers.
Gibbs, the new leader of 3rd Platoon, part of the Army's 5th Stryker Brigade, had served a previous tour in Iraq and another in Afghanistan, and at 6 feet 4 inches and 220 pounds, towered over most of the platoon members.
Gibbs took over the platoon, stationed in Kandahar Province, Afghanistan, in November, 2009. It was a low point for the group: A massive roadside bomb had injured their previous leader and left the team rattled. Gibbs wasn't rattled though.
And, as several of his fellow soldiers would later testify, Gibbs promised his men they would have a chance to exact revenge on the "savages," referring to the Afghan civilian population they were meant to protect.
Nearly two years later, Gibbs, 26, faces a military court martial on Friday for numerous charges, including the murder of three Afghan civilians.
He is the highest ranking soldier charged in what prosecutors say was a rogue "kill squad" that allegedly targeted Afghan civilians and made the deaths look like casualties of Taliban counterattacks.
He has also been charged with removing body parts from his alleged victims, such as teeth and fingers, to keep as souvenirs; planting "drop weapons" to fake attacks on soldiers; and intimidating several of his own unit members from speaking out against the unit's alleged murder plots and rampant drug use.
After his May 2010 arrest in Afghanistan, Gibbs showed investigators a tattoo on his lower left leg depicting crossed pistols and five skulls. He told investigators the skulls were a way to keep track of his kills in both Iraq and Afghanistan, according to investigative interview notes shown to CNN.
Gibbs has pleaded not guilty. His attorney Phillip Stackhouse did not respond to CNN's requests for comment. Stackhouse said in a preliminary hearing this summer that Gibbs acted lawfully and that other soldiers who have testified against him were unreliable witnesses.
Gibbs, a Billings, Montana, native who is married with a young son, faces life in a military prison. His trial is expected to last a week.
Twelve soldiers from the Army's 5th Stryker Brigade have been charged in the case, including five with murder. Three of the soldiers charged with murder -- Spc. Adam Winfield, Pvt. Jeremy Morlock, and Pfc. Andrew Holmes -- have pleaded guilty in exchange for their testimony. Spc. Michael Wagnon has pleaded not guilty to a single charge of murder, and awaits court martial.
Several of the soldiers charged in the case documented the alleged murders through unsanctioned photographs of the bodies. In one of the photos, soldiers hold up a dead man's head and pose alongside the corpse, like a hunting trophy.
In March, these photos were obtained and published by German publication Der Spiegel and Rolling Stone magazine, generating comparisons to the Abu Ghraib scandal, and causing the Army to issue an apology.
Prosecutors have portrayed Gibbs as the kill squad's alleged ringleader. But according to testimony in the court martials of other soldiers, he didn't have to push many of the soldiers very hard to take part in the killings which he referred to as "scenarios."
"It wasn't a completely new conversation," Pvt. Jeremy Morlock testified during a July hearing. "It wasn't far-fetched. Rolling around our minds I guess."
Getting away with murder
Gibbs openly discussed how easy it would be to kill Afghan civilians and then make them appear as if they were insurgents, other soldiers have testified. They said they thought Gibbs was joking.
Morlock said the alleged "kill squad" soldiers carried out the executions spur of the moment.
"There was never anything planned," he testified. "Like this date or this time. We found an opportunity."
The first "opportunity," Morlock testified, came in January 2010 during a patrol of a village called La Mohammad Kalay. Morlock told investigators that he and another soldier, Pfc. Andrew Holmes, spotted a teenage farmer named Gul Mudin alone in a field. They beckoned him closer.
"I could see his hands were empty," Holmes testified. "He didn't have a weapon."
Morlock testified he then threw a grenade and ordered Holmes to open fire. The blast ripped the man apart. Morlock testified that the grenade was "off the books" -- one that couldn't be traced back to him. It was, he said, given to him by Sgt. Gibbs.
As Mudin lay dying, Morlock and Holmes later testified, they told fellow soldiers the Afghan farmer had tried to attack them with the grenade. Against military regulations, the men posed for photographs with their "kill."
Both Morlock and Holmes pleaded guilty as part of separate plea deals with prosecutors. Morlock is serving a 24-year sentence for killing Mudin, and two other unarmed Afghan men, and Holmes was sentenced to seven years in military prison.
Morlock testified that he boasted about the shooting. Soon, word spread about the alleged "kill squad" among their fellow soldiers on base and even among some family members back home.
"People in my platoon ... can get away with murder," Spc. Adam Winfield wrote his father on Facebook on February 14, 2010. "Everyone pretty much knows it was staged."
Chris Winfield was stunned when he read his son's message. He tried to report his son's account and even, he said, called Joint Base Lewis-McChord where the division is based.
He said his warnings were not heeded.
Adam Winfield testified that he later told his father that he was afraid for his own life and not to seek any more scrutiny for the unit's alleged activities.
'They were not posing any threat to us'
In February 2010, the squad went on a mission to a village called Kari Kheyl. There, Gibbs, Morlock and Spc. Michael Wagnon entered the hut of man a named Marach Agha. They ordered Agha outside and then, according to Morlock, Gibbs turned to the other two soldiers.
"'Were we okay to go ahead and shoot this guy?'" Gibbs asked the soldiers, according to Morlock's testimony. "We said 'yeah.'"
Gibbs first fired a contraband AK-47 into a wall, Morlock said, to simulate enemy fire. Then with his M4 rifle, Gibbs shot Agha, Morlock testified. Morlock said he and Wagnon also fired rounds to make it appear as if the soldiers had been attacked first.
Wagnon is charged with Agha's killing and has pleaded not guilty.
In March 2010, while on patrol, Gibbs spotted two Afghan men who he said were carrying a rocket-propelled grenade launcher. But what the men held was actually a shovel, Staff Sgt. Robert G. Stevens, a medic who was also on the patrol, later testified.
"They were not posing any threat to us," Stevens said. Gibbs ordered the soldiers to shoot them, according to Stevens. The medic told the court he intentionally shot 75 yards away from the Afghans, who fled.
"Sgt. Gibbs said we needed to work on our accuracy," Stevens testified, "Because it did not appear that we hit anyone."
As part of a plea deal, Stevens was sentenced to nine months in prison for that incident and for faking an insurgent attack on a nighttime Army vehicle convoy with a grenade.
After he threw the grenade, Stevens testified, soldiers in the convoy fired at nearby Afghan huts. Stevens said he did not believe any Afghans were hit. None of the soldiers in the convoy were injured by explosion.
Combat decorations awarded to the soldiers were later rescinded after investigators discovered Stevens had thrown the grenade.
Stevens testified that Sgt. Gibbs gave him the grenade hidden in a sock. Also in the sock, Stevens testified, was a human finger.
In May 2010, Gibbs, Morlock and Winfield were among soldiers on a patrol in a village called Qualaday. In the three months since writing his father on Facebook, Winfield had shifted from wanting to expose Gibbs to trying to get into the sergeant's good graces.
Winfield was afraid of his sergeant, he would later testify, and his easy talk of covering up murders in a war zone.
In Qualaday, Winfield testified, the three men singled out a man named Mullah Allah Dad, the local cleric, and led him away from the compound where he lived with his wife and children. Winfield said Gibbs ordered the man to kneel in a ditch.
"I had an idea that Sgt. Gibbs was looking for a kill," Winfield told the court. Then, with Winfield and Morlock shielded behind a low wall, Winfield said Gibbs threw a grenade at Allah Dad. The explosion, he said, ripped the cleric apart.
Morlock and Winfield next opened fire to simulate a firefight and then the soldiers planted a grenade near the man, Winfield testified.
Depressed over his role in the incident, Winfield said he grew afraid that Gibbs might want to silence him. While walking across base to talk with a chaplain, Winfield said Gibbs suddenly intercepted him.
"Sgt. Gibbs reminded me I shouldn't be talking about things I shouldn't be talking about," Winfield testified.
Winfield said Gibbs warned him that he could kill Winfield and make it look like an accident.
Meanwhile Gibbs' behavior was becoming more outlandish, other soldiers said. According to the soldiers who testified at preliminary hearings in Gibbs' case, he showed off fingers and teeth he had removed from corpses and discussed throwing candy onto roads.
The sweets would draw children who they could then run over, he allegedly theorized.
'Kill squad' unravels
The unraveling of the alleged "kill squad" came about not from targeting Afghans but after prosecutors said Gibbs organized an attack on a fellow soldier.
Three days after prosecutors say Gibbs killed Mullah Allah Dad, he and six other soldiers confronted Pfc. Justin Stoner. The soldiers were furious at Stoner for ratting them out for abusing drugs.
According to prosecutors, several of the soldiers used Stoner's room to smoke hashish they bought from Afghan translators. Stoner, according to prosecutors, was afraid he would shoulder all the blame for the drug abuse and complained to superiors
The soldiers began to beat Stoner, prosecutors charged. After the alleged stomp down, according to prosecutors, Gibbs showed Stoner fingers he allegedly cut off the corpses of dead Afghan men
The alleged threat backfired though and Stoner soon was talking about the drug abuse, the beating and killings of civilians to investigators.
Gibbs was arrested in May 2010 in Afghanistan and on Friday, he faces those charges in a military courtroom some 7,000 miles away from the Afghan villages he is accused of terrorizing.
Even though none of the soldiers' officers have been charged for participating in or knowing about the alleged kill squad, they bear some responsibility for the unit's actions, Stjepan Mestrovic, a sociology professor at Texas A&M University told CNN in an interview..
"There was a focus on body counts and aggression throughout the brigade," said Mestrovic who testified for Morlock's defense and was permitted to review documents in the case including a sealed report on what the brigade leadership knew.
Mestrovic described a "dysfunctional command climate" where officers disregarded the military's declared counterinsurgency mission of engaging and winning support with the local population.
"In this climate there was a 'kill board,'" Mestrovic said, describing the way in which units were ranked for how many Taliban they had killed. "They had a brigade commander who wanted a high body count, who was constantly preaching to search out and kill the enemy rather than what they mockingly called 'go and have tea with the village elders.' "
But prior to Gibbs' arrival, the unit hadn't had any kills, Mestrovic said, and was being pushed to be more aggressive with an enemy that preferred to ambush rather than directly engage them.
The soldiers' frustration and boredom became a toxic mix, Jeremy Morlock testified. "We lost fellow soldiers to IEDs and lived in fear of being killed by them on a daily basis. ... I just wanted to survive and come home in one piece," Morlock told the court. "I realize now I wasn't fully prepared for the reality of war as it was being fought in Afghanistan."
"Soldiers were basically left on their own," Mestrovic said. "The distinction between an enemy and a civilian broke down. They saw everyone out there as an enemy."