He came to national attention in the United States after he was charged in September 2018 with ten offenses under the Uniform Code of Military Justice.

In the most prominently reported offense, he was accused of fatally stabbing an injured 17-year-old ISIS prisoner, photographing himself with the corpse, and sending the photo to friends.

[10] Only after the reports gained visibility outside the SEAL community, were they acted upon and referred to the Naval Criminal Investigative Service (NCIS).

[6] On October 18, Lieutenant Jacob Portier of Gallagher's platoon was also charged with failing to properly notify his superiors within the chain of command and destruction of evidence.

[12] According to two SEAL witnesses, Gallagher said "he's mine" over the radio, then walked up to Abdullah and allegedly proceeded to stab him with his hunting knife without explanation.

[1] Gallagher also was reportedly known for indiscriminately spraying neighborhoods with rockets and machine gun fire with no known enemy force in the region.

[14] According to the original Navy prosecutor Chris Czaplak, "Chief Gallagher decided to act like the monster the terrorists accuse us of being.

[5] The case was considered to be "difficult"[15] because the Navy did not begin a formal investigation for nearly a year after the reports were made and by then much of the physical evidence, such as the bodies of those alleged to be killed by Gallagher, were not recoverable.

[12] The prosecution's case relied largely on eyewitness testimony, which the defense sought to discredit as merely that of spiteful malcontents who disliked Gallagher's gruff leadership style.

[16] The defense argued that Gallagher's text messages merely reflected dark comedy in a stressful situation, and that his more outrageous boasts, such as killing twenty people a day, were clearly impossible.

[1] The defense also claimed that the lead NCIS agent slanted witness statements and interviews to be more hostile to Gallagher than warranted in his notes.

[8] On March 30, President Donald J. Trump intervened and ordered Gallagher transferred to "less restrictive confinement" after complaints from his supporters, particularly commentators on Fox and Friends, about his detainment.

[18][19][20][21] In May 2019, defense lawyers accused the prosecution of sending both them and Navy Times reporter Carl Prine an email that included a Web beacon.

[15] As a result of the spying controversy, the judge ordered Gallagher freed from prison while awaiting trial as a remedy to interference from the prosecution.

[23][24][25][26] On May 8, 2019, then Republican Congressman Duncan D. Hunter showed combat video footage from a helmet camera to a group of legislators that he said exonerated Gallagher of one of the charges against him.

[27] According to anonymous administration sources, the Justice Department was reviewing Gallagher's case in preparation for a possible pardon from President Trump.

[29][21] The Daily Beast and CNN later reported that Fox & Friends co-host Pete Hegseth had sought to convince Trump to support and pardon Gallagher for months.

[30][31] During a podcast interview on May 28, 2019, Hunter said that he himself had posed for pictures with a dead enemy combatant and that American artillery fire had killed "hundreds" of Iraqi civilians in and around Fallujah.

And while press reports suggested Scott could conceivably be charged with perjury, the Navy dropped its investigation into his statements shortly after Gallagher's acquittal.

[35] After the trial, it was considered possible that Special Warfare Operator 1st Class Corey Scott, the SEAL Medic whose surprise testimony dismantled the prosecution's case, would be prosecuted for perjury; however, Chief of Naval Operations John M. Richardson stripped Navy prosecutors of their authority to charge Scott with perjury.

[19] The president's move also favored several other military members accused of misconduct: in addition to Gallagher, Lieutenant Clint Lorance was ordered freed; and the prosecution of Matthew Golsteyn was ended.

[47] Following his acquittal, Gallagher spoke publicly about the case, appearing on Fox News without authorization, and using social media to describe his superiors, including Rear Admiral Collin P. Green, the newly installed commander of the SEALS, as "a bunch of morons".

Associates said Spencer would resign if such an order is issued, believing it undercuts his authority and that of Rear Adm. Collin Green, commander of the SEALs.

"[55] After the verdicts, sentence and pardon, the New York Times revisited the case and accessed, using the Freedom of Information Act (FOIA), investigative reports and also videos of interviews in which six SEALs under the command of Gallagher had separately extensively detailed his ongoing prohibited combat zone behavior, sometimes crying as they recounted the abuse.

Following his Navy career, Gallagher began commercial ventures including an action figure, clothing line and nutritional supplement endorsements.

Gallagher openly discussed topics including his career, the raid upon his home, pre-trial confinement, legal proceedings, acquittal, retirement, and his life and family.

In that episode, (Shawn Ryan Show #008) Chief Gallagher explained in depth how teammates under his command at SEAL Team 7 not only accused him of being a war criminal, but relentlessly tried to send him away to life in prison for the alleged stabbing of an Islamic State fighter in Mosul, Iraq.