"What?"
"What? I hear bullshit, I say bullshit. It's a thing I have, you know."

Charlie Cale is "a human lie detector". In Episode 1.01 of Poker Face, she describes her ability as follows:
Ehh yeah, no, I only know if something is a lie. And outside of poker, less useful than you'd think. 'Cause everyone, they lie constantly. It's like birds chirping, people lying. Just once you tune into it, it's fucking everywhere all the time. And they usually don't lie to cover up some deep, dark secret, but about the stupid, meaningless shit, you know. So, the real trick of it is to figure out why. Why someone is lying.
This ability works over video, and also when she hears a voice, even over the radio. It's never explained, but the world of Poker Face is lacking in supernatural or magical elements, so we can perhaps put this down to a powerful instinct for grasping microexpressions and vocal intonation.
Charlie will not call you out on lying unless she thinks someone is going to be hurt by the lie, or if it's a matter of life and death. Otherwise, she'll let it slide as "birds chirping". But if you want any limitations on this ability, or just flat don't want to deal with it, please leave a comment below. Thanks!