I have been researching and teaching advanced investigative interviewing for over twenty years. "The Truth About Lies" although well produced, is disappointingly predictable in it’s uncritical promotion of self-serving tidbit psychology. Paul Ekman’s FACS, (facial action coding system), and much of the new show “Lie to Me” is based on the dubious notions that our intuitive powers are ineffectual and that articulated instruments devised by experts are far more effective at revealing liars. There is no doubt that behind our everyday stoic masks we often reveal momentary and minute emotional expressions. The problem is in the translation of expression to credibility involves a whole set of variables including preconceived notions and the needs of the interpreter. If you look at any of the examples of the effectiveness of FACS you will notice one common feature. The public already believes these people are liars. There is no risk for the researchers making assertions that they can distinguish the meaning of expressions when one is already certain the subject is a liar. Take for example the clip in “The Truth About Lies” of a researcher decoding the expressions of contempt, disgust and anger of a murderous husband. Stress about a missing loved one will manifest a whole range of intense labile emotions. A spouse may feel rage toward an imagined abductor, contempt or disgust toward an ineffectual or indifferent investigation, all emanating from the racing mind of a panicked and innocent suspect.
There are many factors that lead to the detection of deception, including expectation, time, observation, risk, context, sophistication and ultimately how desperately you want to know the truth. Trustworthiness is often based not on knowledge or experience, but on our need to rely on others in our ignorance. This includes psychologists, who we want to believe make sense of our behaviour with unshakable facts, whether or not it is well founded. There are two things I have learned after years of research. Your detecting skills are far better than the experts are telling you and experts are far less capable than you are being led to believe.

That's encouraging to hear Dana, I still figured my gut feelings were pretty reliable, just based on how often it seems to turn out accurate.
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A stranger could probably decieve me easily enough, but the longer I know someone the better I can tell. I'm not sure if that's through any sort of micro-expressions, or more that I've been able to observe how well their words line up with their actions.
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What gets me is when somebody is dishonest with themselves. Sometimes I feel that a person is being genuine with me, they truely believe what they're saying, but I suspect it's self-deciet.

Instinct is often played down, it's true - if you know someone well enough their 'truth' often speaks louder than their words, tone of voice and mannerisms combined give the real answer. Fleur