hypothetical legal question

Today I was talking to a friend, and he mentioned smoking up on a particular field in a nearby park. I told him that it was dangerous to do it out in the open there, and that he should get stoned first and THEN go to the park. He joked that if a cop ever approached him or anything, he'd just swallow his joint. I'm wondering, would this keep him from getting in trouble? I mean, the cop might smell weed, but if he swallows it and has nothing on him, can he still get in trouble with the law?

the cop will try to sneak up on you and take it from you, and if he can't, then he'll search you for a baggy or anything he could get you with possesion for.

what if the baggy's empty but it smells like weed?

yea i was wonderin that too. if u smell like weed or anything but have nothing on u can u still get arrested or a ticket or whatever the penalty is.