Though they are not perfectly accurate, they are generally indicative, so it's useful in a statistical game. Border agents are trained to look for all sorts of

Though they are not perfectly accurate, they are generally indicative, so it's useful in a statistical game. Border agents are trained to look for all sorts of things, none of which make you guilty, but a few of which may make you suitable for more questions or a quick search. So I'd imagine it'll get used in the same context.