The use of reasonable force to protect oneself or members of the family from bodily harm from the attack of an aggressor, if the defender has reason to believe he/she/they is/are in danger. self-defense is a common defense by a person accused of assault, battery or homicide. the force used in self-defense may be sufficient for protection from apparent harm (not just an empty verbal threat) or to halt any danger from attack, but cannot be an excuse to continue the attack or use excessive force. examples: an unarmed man punches allen alibi, who hits the attacker with a baseball bat. that is legitimate self-defense, but alibi cannot chase after the attacker and shoot him or beat him senseless. if the attacker has a gun or a butcher knife and is verbally threatening, alibi is probably warranted in shooting him. basically, appropriate self-defense is judged on all the circumstances. reasonable force can also be used to protect property from theft or destruction. self-defense cannot include killing or great bodily harm to defend property, unless personal danger is also involved, as is the case in most burglaries, muggings or vandalism.