This artist’s rendering shows Massachusetts Air National Guardsman Jack Teixeira, right, appearing in U.S. District Court in Boston, April 14, 2023. (Margaret Small/AP)

BOSTON — A member of the Massachusetts Air National Guard who pleaded guilty to leaking highly classified military documents about the war in Ukraine is to be sentenced in federal court on Tuesday.

Prosecutors argued that Jack Teixeira should be sentenced to 17 years in prison, saying he “committed one of the most significant and significant violations of the Espionage Act in American history.”

“As a member of the United States Armed Forces and a warrant holder, the defendant took an oath to defend the United States and to protect its secrets—secrets that are vital to the national security of the United States and the physical safety of Americans who serve abroad increase,” prosecutors wrote. “Teixeira broke his oath almost every day for over a year.”

Teixeira’s attorneys will argue that U.S. District Judge Indira Talwani should sentence him to 11 years in prison. In the sentencing memorandum, they acknowledged that their client “made a terrible decision that he repeated for 14 months.”

“It is a crime that deserves serious consequences,” the lawyers wrote. “Jack has fully accepted responsibility for the injustice of his actions and is prepared to accept whatever punishment must now be meted out.”

Teixeira, of North Dighton, Mass., pleaded guilty in March to six counts of withholding and intentionally transmitting national defense information under the Espionage Act. This came nearly a year after he was arrested in the most significant national security leak in years.

The 22-year-old admitted to illegally collecting some of the nation’s most sensitive secrets and sharing them with other users on the social media platform Discord.

When Teixeira pleaded guilty, prosecutors said they would seek a prison term at the upper end of the range. But the defense wrote that 11 years was “serious and appropriate to take account of deterrence considerations and would essentially be equal to half the life that Jack has lived so far”.

His lawyers described Teixeira as an autistic, reclusive individual who spent most of his time online, particularly with his Discord community. They said his actions, while criminal, were never intended to “hurt the United States.” He also had no criminal record.

“Instead, his intent was to educate his friends about world events to ensure they were not misled by misinformation,” the lawyers wrote. “For Jack, the war in Ukraine was his generation’s World War II or Iraq, and he needed someone to share the experience with.”

Prosecutors, however, contested that Teixeira does not suffer from an intellectual disability that prevents him from knowing right from wrong. They argued that Teixeira’s post-arrest diagnosis as having “mild, high-functioning” autism “is of questionable relevance in these proceedings.”

The security breach raised alarm over America’s ability to protect its most closely guarded secrets and forced the Biden administration to try to contain the diplomatic and military fallout. The leaks have embarrassed the Pentagon, which has tightened controls to protect classified information and disciplined members who were found to have willfully failed to take necessary action on Teixeira’s suspicious behavior.

Teixeira, who was with the 102nd Intelligence Wing at Otis Air National Guard Base in Massachusetts, worked as a cyber transportation systems specialist, which is essentially an information technology specialist responsible for military communications networks. He remains in the Air National Guard in an unpaid status, an Air Force official said.

Authorities said he first typed the classified documents he accessed and then began distributing photos of files marked SECRET and TOP SECRET. Prosecutors also said he tried to cover his tracks before his arrest, and authorities found a broken tablet, laptop and Xbox game console in a dumpster at his home.

The leak exposed to the world unseen secret assessments of Russia’s war in Ukraine, including information on troop movements in Ukraine and the provision of supplies and equipment to Ukrainian troops. Teixeira also admitted to posting information about a US adversary’s plans to harm US forces serving overseas.