Witness accounts and graphic photos of a Navy SEAL out of control while deployed to Iraq, U.S. Navy prosecutors said in military court at Naval Base San Diego.
Special Operations Chief Edward Gallagher arrived at court Wednesday in his uniform and handcuffs.
U.S. Navy prosecutors accuse Gallagher of premeditated murder for the stabbing death of an injured ISIS fighter who they estimate was about 15 years old.
The stabbing happened in Mosul, Iraq in May 2017.
Gallagher is also charged with aggravated assault for shooting Iraqi civilians. Prosecutors want those charges increased to attempted murder.
On Wednesday, the Navy outlined its evidence including cell phone photos that show Gallagher holding the severed head of the fighter during a reenlistment ceremony.
That evidence is considered privileged and was not shown in court because it could be used as propaganda by enemies of US troops.
The government also said it had a video of the Iraqi fighter before he was killed.
An NCIS investigator testified about interviews with witnesses to the alleged stabbing death and other possible crimes.
Gallagher's private defense attorney questioned conflicts in dates and testimony in court and Asked if investigators were able to determine if the ISIS fighter could have died from injuries suffered in an airstrike.
The defense says Gallagher was turned in by his subordinates because he was too tough on them.
Gallagher was arrested on Sept. 11 at the Camp Pendleton Intrepid Spirit Center.
He is also accused of encouraging members of his platoon to stay quiet about what happened in Iraq, the Navy Times' Carl Prine reported. Those conversations allegedly took place in and around San Diego between April and September when he was arrested, he reports.
Prine reports the NCIS investigation targets several SEALs who deployed to Iraq between 2017 and early 2018 as well as senior enlisted and commissioned leaders in Naval Special Warfare Group 1.
The Navy SEALs Fund Brotherhood Beyond Battlefield has launched a fundraising campaign for Gallagher who served eight tours of duty with six as an elite special forces operator.
Gallagher has served 19 years in the U.S. Navy and more than 14 years as a Navy SEAL, his attorney said.
In 2017, Gallagher was ranked as the top SEAL chief and his platoon was ranked as the top SEAL platoon, the website said.