I didnt read many other comments, but on my senior prom night of highschool a friend and I got busted hotboxing outside of the party house (at like 3AM in the back of a neighborhood, wtf). We had over an eighth (sep. baggies too), two pieces and a grinder... we told the cop we only had an eighth and just smoked a joint (he asked about the smell before he even introduced himself as a cop). We handed him the weed and only weed and he crushed it into the pavement. He let us off, left, then we scraped up about a gram of (still crystally and sticky) bud and smoked it. We also lied (always a terrible idea) about not having anything else in the car.
If you're under the influence of anything, when you tilt your head back and close your eyes they will twitch a lot. When your eyes are twitching behind closed eyelids and a light is shining on your face (god damn police flashlights) it's extremely noticeable and very hard to control.