The TV show Lie to Me poses the theory that "micro-expressions" that appear and disappear on the face can be used to definitively determine if a person is lying or telling the truth. This is a case of Truth in Television, as the science of micro-expressions has been around for a long time; psychologist Paul Ekman has written a number of books that show how this can be used to detect lying, honesty, and other emotions and private feelings. His 1985 book Telling Lies inspired the show.
In the show, there are some people who can automatically tell if a person is lying because of their micro-expressions; these people are "hyper-aware" and can pick up even fleeting expressions. In reality, this is harder; most experiments use slow-motion cameras, because subjective human opinion can be swayed by other evidence and by personal feelings. The practice of using micro-expressions to root out lies and deception has been implemented in some parts of business and national security, but is not entirely successful to date.