How to Tell When the NSA is Lying to You
Imagine you are running a spy agency, and you are trying to watch a specific person. The crucial element of spying is to be sure that your subject does not know you are spying on them. Once your cover is blown, any information that the subject might divulge is probably useless, or even intentionally misleading. Your cover is essential to getting useful information.
Now, imagine that you are the NSA, and your mission is to spy on everyone on the planet. Then, you are asked to stand before Congress (and the entire world) and testify to the nature of your program.
They ask you, "Are you spying on Americans?"
The stock answer, without even thinking, must be "No." If you say "Yes," any valuable information being exchanged in the United States is promptly cut off. You directly damage your program if you provide any truthful information as to who, when, where or how you are spying on people. Even admitting the program exists is a shot in the foot.
They ask "How many employees do you have?" and "What kind of computers do you use?"
Is telling the truth any help to you? If your targets know your capabilities, they can thwart your efforts. Any information, from how long you store information to how your screening system works, can all be used against you if it becomes public. Your ideal scenario is to be spying on everyone without anyone knowing anything about your program.
Ultimately, it is essential to the success of your mission to lie about absolutely everything and reveal nothing. Any shred of truth can damage your mission, regardless of how trivial, and so it is imperative that you lie.
So how do you know when the NSA is lying to you? When their lips are moving.