Well if they catch you staring, just quickly switch your eyeballs and stare at something different (or stare right past him) but still keep your same postion....that way, it would look like you've been staring into space and not him! Then when he looks away again, you can switch your eyeballs back on him!
lol been there, as one of the above posters said just avert ur eyes but dnt move so its less obvious. Only thing i ever do norm. If i get caught i sumtimes went bright red, at that point i was beyond hope of denial lol