When the police ask, you can say that you were attempting to design a better car alarm (When the thief screams).
I thought about wiring a sparkplug into the gas tank of my old Z..... that would teach the dumb ass that kept trying to steal it. The one time he succeeds in hot wiring it and BOOOM. Yeah, it might be mean, but not half as mean as if I walked up when someone was screwing with my car.