Well this question should get some interesting responses. IMHO a potentially lethal trip wire "boobie-trap" that fires a shell and harms a trespasser without warning will make you the criminal in a U.S. court of law. You'd probably get free room and board with "Bubba" sharing a nice 9x5 prison cell, and then the trespasser will take all your worldly possessions with a civil lawsuit. And even if your trip-wire contraption isn't lethal and uses a fireworks charge like a cherry bomb or M80 (also illegal in a lot of states) you run a risk. Better off with a good guard dog, auto-lights around the property and blaring horns as a security system. Best of luck.
