Trespassers Beware

Our rental property is on an acreage close to town. We have lots of bushes to hide behind and trees to hang out under. It means we get some pretty cool wildlife: bears, deer, coyotes, raccoons, and an array of predator birds. It also means we get all of the local teenagers sneaking onto our property to hang out and drink their shitty beer. While I know they are not really harming anyone or anything, it irks me that people are trespassing onto our property. My meds already make me paranoid enough to believe that I am being followed, the last thing I need is 16 year olds sitting in our yard with the ability to look through our windows. Fuck, I feel like an 80 year old man with a stick that I like to shake at the world. I am also concerned about the legalities involved... If something happens to them while on our property (mostly I am concerned if our dog attacks them) how liable are we? What if they start a fire in the brush with their cigarettes? What if someone passes out and dies? Today as I was picking up the dog shit in the yard, I was so tempted to dump the collection along the path and around the hangout spot - but I don't want to fuck with karma. Perhaps a giant spotlight will scare them off next time....