The Navy SEAL allegedly boasted about the number of people he had killed, including women, according to the testimonies.
Stabbing a teenage prisoner to death, picking off a young girl and an old man with a sniper rifle and firing a heavy machinegun into a residential area: these are some of the charges facing an elite U.S. Navy SEAL on trial for war crimes while deployed in Iraq.
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Special Operations Chief Edward Gallagher, a decorated 39-year-old veteran of combat missions in Iraq and Afghanistan, is still a hero in the eyes of many U.S. citizens and the rightwing Fox News channel - and his case may even become a factor in next year's presidential elections.
Around 40 Republican members of Congress have written an open letter demanding Gallagher - who denies the charges against him - be set free until he stands trial. One has even called on President Donald Trump to step in and have the case dismissed.
Trump has weighed in on the case on Twitter, saying that he had intervened to ensure that Gallagher "will soon be moved to less restrictive confinement while he awaits his day in court."
Trump said the move was made "in honor of his past service to our Country."
Gallagher, a platoon commander of SEAL Team 7, will face a military tribunal at a Navy base in San Diego on May 28. He was arrested last September and has been held at the base ever since.
He was arrested after men under his command in the elite Navy unit were so horrified by his actions that they complained to their superiors, but were warned that their accusations could damage their careers, according to reports in The Navy Times and The New York Times this week.
Gallagher now faces charges of premeditated murder, attempted murder and obstruction of justice. He could be sentenced to life in prison if found guilty.
The crimes he stands accused of were committed in 2017 during a deployment in the northern Iraqi city of Mosul. U.S. special forces were fighting alongside Iraqi troops to take back parts of the town from Islamic State group fighters.
His lawyer did not respond to an AFP request for comment.
According to testimony at a preliminary hearing last November, members of Gallagher's Alpha platoon were so disturbed by his behavior that they tampered with his sniper rifle to make it less accurate, and would fire warning shots to make civilians flee before he could open fire on them.
"They said they spent more time protecting civilians than they did fighting ISIS," Special Agent Joe Warpinski of the Naval Criminal Investigative Service told the military court.
In May 2017, Iraqi troops captured a wounded teenage Islamic State fighter who appeared to be around 15 years old.
Two members of the SEAL team said that as a medic was treating the fighter's wounds, Gallagher stepped up without a word and stabbed the prisoner in the neck and side several times.
He then posed for a photo holding up the teenager's head in one hand and the knife in the other, the two SEALs said. He went on to stand over the youth's body and perform a re-enlistment ceremony while another member of the team held up a U.S. flag, they said.
According to the charge sheet, soldiers from his unit tried on several occasions to alert their superiors about the alleged war crimes, but without success. Seven of them said they were told they could face retaliation if they went public with the case, but finally managed to bring their concerns to a higher-ranking officer.
Gallagher's commanding officer, Lieutenant Jacob Portier, reportedly posed in the photo with the dead teenager and is himself facing charges for failing to report the crimes and for destroying evidence.
Navy prosecutor Chris Czaplak said Gallagher had "handed ISIS propaganda manna from heaven" by deciding to "act like the monster the terrorists accuse us of being."