Borrow a coin from the spectator and you're ready. The spectator can hide the coin whichever hand he wants, without your knowledge. Then you can detect where the coin is. Not once but twice at a time, 100% accurate. Spectator do not give any information from start to finish. This is impossible to reverse engineer.

No billets
No gimmicks
No questions
No guessworks
No liar/truthteller