Deadly force is justified in cases where the individual feels it is necessary to defend them selves or others against murder, great bodily harm, rape, or kidnapping. This applies to the person's home, place of business, or anywhere the person has the right to be.
Castle Laws are laws that address the use of force when defending one's self inside their home, or on their property. Some states expand this to vehicles, and the person's place of work. Castle Laws generally include: the places where this law applies, the requirements fro use of deadly force, if there is a duty to retreat, the amount of force that maybe used in defending one's self or others. These vary widely from state to state.