All states have self-defense laws that allow people who are threatened to use reasonable force to defend themselves or others, and to avoid criminal liability from their use of force. However, each state has its own rules governing the use of force in self-defense, and any use of force that occurs outside the bounds of the state's laws can result in a criminal conviction. For example, a person who is attacked may fight back, but may not necessarily use deadly force. A person who sees an incapacitated person in danger of being sexually assaulted may intervene to protect the person, but may not pull the person to safety and then attack the assailant.
Self-defense is one of several so-called "affirmative defenses," which include insanity. For more on affirmative defenses, see Affirmative Defenses in Criminal Cases.
Generally, claims of self-defense only come into play when the defendant is accused of a violent crime, such as assault, battery, manslaughter, or murder.
Defendants who claim self-defense admit that they used force or violence against the victim, but they assert that they did so because the "victim" was actually the attacker, that they had to act to avoid being hurt themselves (or to protect someone else from being hurt), and that the amount of force they used was proportional to the threat presented. The basic issues in any self-defense claim are who started the incident and whether the defendant's response was necessary and proportionate to the threat posed by the agressor.
Generally, people cannot claim self-defense when they are the ones who instigated the fight, although there are some exceptions. For example, imagine a husband and wife get into a verbal disagreement. The wife slaps the husband and he retaliates by trying to stab her with a knife. The wife grabs the knife from him and uses it in self-defense. In this case, the wife might still be able to successfully claim self-defense, even though she was not totally innocent, because the husband greatly escalated the use of force. The husband, however, would not be able to assert a good self-defense claim because his response was disproportionate.
People can use reasonable force to prevent an attack too, but the threat of harm needs to be imminent. For example, suppose two football fans get into an argument in a sports bar. One clenches his hand into a fist and the other immediately punches him in the face, knocking him to the ground. The fan has a good self-defense claim, because the other person was about to hit him, and people are allowed to use self-defense to prevent an imminent attack.
Generally, a defendant can use a "reasonable" amount of force in self-defense. What is reasonable depends on the circumstances. The most important circumstance is how much force the victim is using. Defendants who use more force than necessary to protect themselves or others can still be found guilty of a crime, just like the husband in the example above. Consider another example: two parents get into an argument at a Little League game. Things get heated and little Timmy's mother slaps little Suzy's mother across the face. In response, Suzy's mother pulls a gun out of her bag and fires it at Timmy's mom. Suzy's mother has no valid self-defense claim because a slap in the face does not justify shooting at someone; she can be charged with and convicted of assault with a deadly weapon.
In addition to considering whether the defendant's response was reasonable, in many states the use of deadly force in self-defense (force likely to kill or seriously injure someone) is in a class of its own. In these states, the defendant cannot use deadly force unless the victim first uses or threatens deadly force. There must be some evidence that the defendant was reasonably in fear for his own life, such as when:
In some states, defendants cannot use deadly force in self-defense if they can safely retreat from the attack. For example, in a state that imposes a duty to retreat, a person who is about to be attacked by another partygoer, but who has ample opportunity to leave or otherwise escape the situation, cannot legally pull out a gun and shoot the attacker. However, there are some exceptions to the duty to retreat and it does not apply in all states.
The castle doctrine is the most important exception to the duty to retreat. This idea, based on the notion that "a man's home is his castle," sometimes allows a person to use force, even deadly force, against someone who has entered his home without permission, without trying to escape or retreat. The castle doctrine may apply to a person's workplace as well as home. While specifics of the law vary from state to state, generally, people who are under attack in their own homes don't need to retreat or try to escape, even if they can do so safely. Instead, they can typically use force—even enough force to kill—if they are in apparent danger of serious injury. The theory is that people shouldn't have to run within or from their own homes—that they should be free to defend their "castles."
"Stand your ground" laws extend the no-duty-to-retreat aspect of the castle doctrine to situations outside the home. Such laws are in place in over half the states, where a person who is attacked, even in a public place or even when the person could easily get away, has a right to stand his or her ground and meet force with force. Florida's "stand your ground" law was at issue in George Zimmerman's trial for the murder of Trayvon Martin.
For more information on this case and stand your ground laws, see Stand Your Ground: New Trends in Self Defense Law and The George Zimmerman Verdict: Murder, Manslaughter, and Self-Defense.
The most important evidence to present in support of a self-defense claim is evidence that shows that the defendant did not start the fight and responded with a reasonable amount of force. Self-defense is sometimes referred to as an affirmative defense because the defendant may be required to present some evidence to support the claim.
For more information, see Affirmative Defenses in Criminal Cases.
Defendants can also sometimes introduce evidence that the victim was prone to violence or had attacked the defendant in the past. However, a defendant should take care in deciding what sort of evidence to present. In some states, if the defendant presents evidence of the victim's history of violence, the prosecution is allowed to present evidence of the defendant's history of violence.
The traditional self-defense claim focuses on a response to a contemporaneous or very imminent attack. Today, many states allow people who have attacked their abusers to present evidence that they have been victims of serious domestic violence in the past.
For more information on domestic violence, see Domestic Violence & Abuse.
If you are charged with a crime of violence against another person, such as assault or battery, and you believe you were defending yourself or someone else, you should consult with an experienced attorney who is familiar with the criminal law in your state. An attorney can investigate your case and determine whether the facts support a claim of self-defense according to your state's laws. An attorney can help you protect your rights and obtain the best possible outcome in your case.