I think there are three decent ways to tell if someone is lying: the statement itself (did it contain self-contradictions), the context around the statement (wa

I think there are three decent ways to tell if someone is lying: the statement itself (did it contain self-contradictions), the context around the statement (was their hand in the cookie jar), and credibility (does the person have a history of lying). You can use each of these questions to sway your belief in the truth of a statement, but nothing, short of corroborating facts at hand will give you an absolute assessment. Most of the time you just don't know, and it's a good reminder just how important trust is to a functioning society, and amazing how far some pathological liars can get. Importantly, behavioral queues are often misleading, and a person might be acting nervous for an independent reason, yet register all the behavioral clues of lying.