i used to find trashy people on my dads land all the time, our woods bordered a trailerpark that served the town as the low income houseing area, and they would tear up the land leave trash every where and would down right try to attach us if we confronted them about it. I called the cops on it several times, just got worse. they guys that got cought just came back more probably as f*** you kind of thing.
we finally got my dad to let us put up a big tall permanent fence, hasnt happened ever again.