"Mr. Vinas was, during the darkest period of his life, a terrorist," attorneys Michael Bachrach and Steve Zissou wrote in a court filing Friday that CNN obtained.
"However, we can proudly state that Mr. Vinas took the worst experience in his life and turned himself into one of America's greatest weapons against al-Qaeda. Stated simply, he saved lives, and he helped the United States government substantially dismantle what had been the greatest threat to our nation and to our Western allies."
Vinas pleaded guilty in January 2009 to a variety of terrorism charges. He was the subject of the 2010 CNN documentary "American al Qaeda," which told how an all-American kid from Long Island
became radicalized and traveled to the Afghanistan-Pakistan border region
in 2007 to join al Qaeda. As CNN has reported, his capture in Pakistan in November 2008 was kept secret for eight months because of the highly sensitive information he started giving US authorities within days after they caught him.
Vinas, who is now 34, told US government agents that while out in the tribal areas of Pakistan he had suggested attacks on the Long Island Rail Road
and a Walmart store in the United States, but al Qaeda didn't greenlight either plot. He also revealed he acted as a lookout for approaching Pakistani helicopters as al Qaeda fighters fired rockets during a cross border raid on a US base in Afghanistan. In its filing detailing Vinas' actions as a jihadi, the government made no mention of him directly harming anybody at any point.
'He has provided us priceless information'
In 2010, a senior US counterterrorism official told CNN that Vinas had provided "extremely helpful information" in targeting al Qaeda operatives in the tribal areas of Pakistan.
"Just by talking about what he saw, telling us what houses and streets operatives were living in, identifying how al Qaeda runs its courier networks, he has provided us priceless information," the senior official told CNN. "This was actionable intelligence."
Vinas' arrest coincided with an intensification of the CIA's drone campaign in the tribal areas of Pakistan. US counterterrorism officials have not commented on whether intelligence from Vinas helped with any specific strike. What officials have acknowledged, however, is that he became a powerful resource in the US war against al Qaeda.
"His intelligence was not just useful in the first few weeks after his capture but for months afterward," the senior US counterterrorism official told CNN in 2010.
"Vinas was as valuable as having our own agent penetrate al Qaeda," the official added.
In a submission to federal court in February, the US government acknowledged Vinas' contribution to counterterrorism efforts.
"To say that the defendant provided substantial assistance to the government is an understatement. Indeed, he may have been the single most valuable cooperating witness available to the government and law enforcement agencies with respect to al-Qaeda and associated topics related to the time period in which Vinas (traveled) to and was operational in Afghanistan and Pakistan between 2007 and 2008," the government said.
Vinas "contributed to the opening or closing of more than thirty law enforcement investigations ... (and) he provided the FBI with critical information relating to domestic threats and al-Qaeda external operations planning against the United States," it said.
This information, the government said, also created new leads, identified new targets for investigation, confirmed already existing information and filled gaps in the government's understanding with regard to al Qaeda's threat. The government said it was not possible to disclose more detail because "the extensive information that Vinas provided continues directly to contribute to ongoing law enforcement investigations."
In recent years, Vinas has "directly contributed to the prosecutions of numerous individuals by the U.S. government," including testifying at the 2012 trial of a man who was later convicted in an al Qaeda plot to bomb the New York subway, the US attorney said in the February filing.
"(It's) a well known fact that al-Qaeda's operational capacity has been severely diminished
over the last ten years. ... Mr. Vinas was the proximate cause of that diminished operational capability," his defense attorneys stated Friday.
"What's next for Mr. Vinas?" his lawyers wrote. "He dreams one day to find work as a counter-terrorism expert, essentially turning his lengthy cooperation into a career."
They added that a "target will forever be placed on his back by the groups he cooperated against."