"What did [Snowden[ offer in return for the risk he hoped she would take? The answer was compelling. He knew things that the American public ought to know. The director of the National Security Agency, General Keith Alexander, had 'lied to Congress, which I can prove.' Alexander denied under oath that the NSA had ever engaged in the mass surveillance of Americans that was then going forward under the codenames PRISM and XKeyscore. Citizenfour could also demonstrate that General James Clapper, the director of national intelligence, came no closer than General Alexander to telling the truth. When asked, under oath, by Senator Ron Wyden of Oregon whether the NSA collects data on 'millions or hundreds of millions of Americans,' Clapper had answered: 'Not wittingly.'”
And here's the line: "Clapper’s statement was false in every possible sense of the words 'not' and 'wittingly.'”