"In order to establish self-defense, a defendant has to prove that (1) he was not at fault in creating the situation giving rise to the affray, (2) he had reasonable grounds to believe and an honest belief that he was in immediate danger of death or great bodily harm and that his only means of escape from such danger was by the use of force, and (3) he had not violated any duty to escape to avoid the danger. . . . A defendant is privileged to use only that force that is reasonably necessary to repel the attack." State v. Hendrickson, 2009 Ohio 4416
There is no duty to retreat when defending one's self or others in one's home or vehicle. Deadly force maybe used when an aggressor is illegally entering one's home or vehicle.
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.