The Justice Department on Tuesday notified a Brooklyn man serving a 15-year sentence for supporting terrorism that evidence in his case derived from surveillance conducted without an individual warrant.

Agron Hasbajrami, sentenced in January 2013, is the third criminal defendant since the fall to be told that his prosecution involved surveillance under Section 702 of the FISA Amendments Act of 2008.

The law is being challenged as unconstitutional by Jamshid Muhtorov, a Colorado man who in October became the first criminal defendant to be notified that evidence used against him derived from Section 702.

Another defendant, Mohamed Osman Mohamud, was told in November. Mohamud was convicted of trying to detonate what turned out to be a fake bomb at a Christmas tree lighting in Oregon in 2010. He has not been sentenced.

“We’re only now starting to learn how this warrantless wiretapping statute was used,” said Jameel Jaffer, deputy legal director of the American Civil Liberties Union, which is part of Muhtorov’s defense team.

Last year, the department reversed its policy of not notifying defendants after the solicitor general, Donald B. Verrilli Jr., learned of it and objected to it. Earlier in the year, Verrilli had been under the impression that the department was notifying defendants and assured the Supreme Court that that was the case. The court rejected a constitutional challenge to the law by a group of lawyers, human rights activists and journalists on grounds that the plaintiffs could not prove that they’d been subject to the surveillance. It also reasoned, based in part on Verrilli’s assurances, that a way existed to challenge the law — that is, by a defendant notified that such evidence was used in his case.

Jaffer, who argued the Supreme Court case on behalf of the plaintiffs, said that questions remain about how the Justice Department arrived at its initial policy. “They don’t actually explain how they could have concluded that it was lawful to conceal the role that the FISA Amendments Act played in criminal investigations,” he said. “They haven’t explained their prior policy or how they arrived at it.’’