How polygraph tests work (and can they really tell if you're lying?)

Polygraph tests can supposedly detect when a person is lying. But how can a machine do that, and can we really trust the ...
NPR

The FBI and other agencies are using polygraphs to find leakers. But do they work?

Federal agencies have stepped up their efforts over the past few weeks to find potential leakers, and some — like the FBI, the Department of Homeland Security and the Department of Defense — are ...