FF here.
I didn't start till after I got hired on... but if you're worried about the polygraph, they do ask you if you've done any illegal drugs. Most counties wont test for juice specifically, its too expensive, they just have the basic 5 panel drug test.
If the cop does ask you if you've done any illegal drugs, and you say "no" and the results come back "questionable" he will ask you about it before you even stand up. Example; He asked me to put a dollar amount on everything I have stolen in my life. Obviously you're not going to know exactly how much, but I said "$300" and it came back "questionable" and when he asked me about it, I just said I didn't really know, all I've take is office supplies/pens/etc.. Basically what they are looking for is HUGE differences, like if you've stolen a car or something.
Not sure how you can get around that question, without making something up like "yah I smoked 1/2 joint in high school" or something. Because I'm pretty sure if you say you jooce, you either A: wont get the job, or B: will have a reg flag next to your name.