20/20
I have an unfair advantage I think though. I sit at several poker games a week, and have read many books on "tells". A genuine smile has many uncontrollable effects on the body. If you were looking at their mouth, you stood no chance. Try looking at their ears, eyebrows, forehead, eyes, cheeks, etc... If they "tick" (an uncontrollable jerk of sort) that's a sure sign that it's genuine. In cards, a genuine smile, tick, or tell is as good as gold.
If anyone's into this stuff, I highly recommend reading some of Mike Carro's books.
