Originally posted by twhitehead
Its not about whether the house owner is OK with it, its about whether or not you are committing a criminal offence. Unless he was asked to leave, he would not be committing a criminal offence.
Harming the trespasser in any way would almost certainly be a criminal offence. The correct course of action is to ask them to leave and if they do not, you call the police. Only if you are threatened by the trespasser can you take actions in self defence.
Trespass is a criminal offense. If a home has locked doors, and windows, it is presumed that anyone defeating those measures is trespassing.
A lot has to do with the exact circumstances. If I wake at 3am to the sound of a crowbar prying open my locked door, the offender has already rejected my denial of him entering, and declared criminal intent. If he entered knowing the home is occupied, I would presume his intentions to be to harm anyone inside. In American law, this is known as the "Castle Doctrine", as a man's home is his castle.
I would have no reason not to shoot this intruder, and would not owe him further warnings. Many people post signs to the effect that "burglars will be shot, and survivors prosecuted". Other means of warning off intruders are signs warning of vicious dogs.
I am aware that some jurisdictions have passed laws forbidding dogs, or active alarm systems such as booby traps. I find these wrongheaded, and basically protective of the criminal element.
I find your "ask them to leave" advise particularly foolish in any non urban environment, where police response by be a long time coming. For example, in northern Michigan between the Mac bridge and Escanaba is a stretch of road with a few small towns and almost no police, especially at night. A 911 call there might take an hour or much longer for a response. There are, in fact, many times and places where people must face emergencies on their own, even in urban areas.