Last year, Snowden leaked documents that revealed the extent of some of the surveillance, including one program begun in 2008 that allows the government to read or listen to communications of non-Americans located outside the U.S. for counterterrorism purposes. Defending the programs, the Obama administration has provided even more information about how and when this particular surveillance was used.
These details gave some people accused of terrorism a clearer picture of what evidence might have been used against them that they didn't know about. And this prompted questions about why certain defendants weren't told about this particular surveillance.
The surveillance at issue in the Justice Department review covers communications of non-Americans outside the U.S. Under that provision, known as Section 702, the NSA can also sweep up the domestic communications of any American in contact with the terror suspect, even if those contacts have nothing to do with terrorism. The resulting sweeps are likely to have included emails and other data from tens of thousands of Americans over the past decade, experts have said.
Civil liberties groups challenged the constitutionality of this program in 2008, after it was added to the Foreign Intelligence Surveillance Act. Their case ultimately went to the Supreme Court, which found that they had no standing to challenge the law, because they had no proof that their communications were monitored.
That decision came in February 2013, months before the Snowden disclosures. But, during the course of the Supreme Court arguments, the government stated that it is the government's policy to tell a defendant if evidence derived from this particular surveillance program would be used against him or her.
At that point, no defendant in a terrorism case was aware that the surveillance authorized under that particular law had been used in gathering evidence against him.