You want to calibrate with questions as close as possible to the intensity of the questions you'll be asking. I've heard that voice tone often changes when someone is lying. Since voice tone is pretty unconscious in the Western world, it's often outside the awareness of the liar. So calibrating on voice tone might be another fruitful tack to take. But so far as I know, there's no absolute way to know if someone's lying.
Human beings are far too complex for our current understanding to give definite results.
I hope this helps. Back I have just read the email exchange between yourself and the police interrogation expert. As a newcomer to NLP I have started reading on the subject and have a book list I am working through. I am also looking for real-life examples of what I learn. Today, in a meeting, a colleague told what I believe to be a lie in response to a direct question.