The George Zimmerman case shone a spotlight on Florida’s ‘stand your ground’ law, an extension of the “castle doctrine” which is an ancient common law concept that a homeowner has no duty to retreat when threatened within his or her home by a third party. The castle doctrine exists in law in virtually every state, in some form, including Massachusetts:

Section 8A. In the prosecution of a person who is an occupant of a dwelling charged with killing or injuring one who was unlawfully in said dwelling, it shall be a defense that the occupant was in his dwelling at the time of the offense and that he acted in the reasonable belief that the person unlawfully in said dwelling was about to inflict great bodily injury or death upon said occupant or upon another person lawfully in said dwelling, and that said occupant used reasonable means to defend himself or such other person lawfully in said dwelling. There shall be no duty on said occupant to retreat from such person unlawfully in said dwelling.

Stand your ground laws are essentially extensions of the castle doctrine to outside the walls of one’s personal residence and were generally passed in 2005 or later. On the books of nearly half of the states, stand your ground laws generally allow people to use force (including deadly force) to defend themselves if they feel threatened, and in some states has been extended to include businesses, vehicles and anywhere that the individual is lawfully occupying (such as Florida’s law). These laws include varying degrees of requirements as to when citizens may use deadly force. Prior to these laws being promulgated, citizens were required to flee from an attacker before using force as a last resort.