First, anyone can be sued for anything, anywhere, anytime in this great land of ours
, so there is no way to guarantee you won't be sued. The best you can do is to make sure what you do is reasonable
, so as to better your odds of not losing
Second, there is a huge difference between a guard
dog and a watch
dog. The guard dog is a big dog, extensively (and expensively) trained to defend an area and attack intruders. You do not want this in a residential area or near a family. A watch dog can be as simple as the family pet terrier, who yaps his head off whenever a stranger comes to the door. As someone said earlier, this (like motion-sensor lighting) may be all the unwanted attention needed to ward off a predator and make him move on to another house.
Third, get a shotgun. As my dad once told me, better alive and in court than dead and in the right.