Years before Edward Snowden provided documented proof that the National Security Agency was really a national insecurity agency as it was violating law and the US Constitution and spying indiscriminately on American citizens, William Binney, who designed and developed the NSA spy program revealed the illegal and unconstitutional spying. Binney turned whistleblower, because NSA was using the program to spy on Americans.
As Binney was well known to the US Congress, he did not think he needed any NSA document to make his case. But what he found out was "Congress would never hear me because then they'd lose plausible deniability. That was really their key. They needed to have plausible deniability so they can continue this massive spying program because it gave them power over everybody in the world. Even the members of Congress had power against others [in Congress]; they had power on judges on the Supreme Court, the federal judges, all of them.