Courvoisier v. Raymond

Should the common law excuse harmful contact made in self-defense? If so, how do we decide which harmful acts fall within the scope of self-defense?

Defendant was woken one night by parties who were trying to break into his jewelry store. After the group gained entry, defendant scared them away by shots into the air. Plaintiff—a policeman—approached the defendant, identified himself as an officer, and called out for the defendant to stop shooting. The defendant mistook the plaintiff as one of the trespassing parties and shot him.