Yes, have done! There is no such thing as a lie detectory. The polygraph, used on TV shows, is a discredited bit of pseudo-science that only measures bodily reactions to stress. If you can control stress, you get through - simple as that!
Further more, it doesn't flash up 'true' or 'lie', it produces a print out, a graph showing heart rate, skin conductivity etc. It is up to the operator to interpret this, so essentially, all you are getting is someone's guess. In many cases, this interpretation is not double-blind, the operator is privy to, or even asking, the questions. So it is totally subjective.