Well, to some extent, yes. Why. Who's after you, and what have you done (now)?
Valium would serve to slow the heart rate, but not necessarily other physiological reactions that are largely involuntary. Therefore the reverse would be true to better mask reactions...coffee with a marathon. If your heart is already speeding, you're sweating, breathing is heavy, eye movement is rapid, and you're twitching...and that is the base, the norm, there is then no reaction to be had. And then there's false positives...
Ah, what do I know? (Just a little of many things, and not much on any one thing). It really doesn't matter since they're inadmissible, right cbraver?