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Experts in the field of body language say they can often tell if a person is lying. There may be subtle cues of discomfort. There are also more obvious signs of lying such as stalls or delays to account for thinking time while a person is trying to formulate their lie.
Of course, these experts are people trained especially for interrogation and to read body language, which most of us are not.
Statistics say that people generally do not catch lies about 50% to 80% of the time.
One theory is that that average person is reading the body language, but is discounting it or ignoring it in favor of the spoken word.
The use of mindfulness skills while interacting with another person can greatly enhance our overall understanding of the exchange by paying attention to facial expressions and behaviors that convey much more about mood, attitude, and intention than the words alone. Mindfulness while interacting with others helps us to detect dishonesty in the exchange.
The act of being fully present (mindful) in the conversation will help you read the subtleties of the body language and the unspoken word. This mindfulness practice then broadens the connection and understanding with the other person; it is not solely serving the purpose of detecting a liar.