Duty to Retreat:
Self defense is generally used as a defense to a charge of criminal assault or criminal battery. The requirements that must be met in order for the defense to be successfully raised will differ depending on whether or not the defendant is charged with using deadly force or not.
In all cases where the defendant uses self defense as a defense to a charge of assault or battery, the following five elements must be proven.
First, the defendant must prove that he reasonably believed that his act was necessary to defend himself. This defense is available even if it turns out that the defendant did not actually need to defend himself. As long as he reasonably believed that he needed to defend himself, he will be able to use this defense.
Second, the defendant must show that he reasonably believed that he was being threatened with physical harm.
Third, the defendant must show that the threatened harm was imminent.
Fourth, the defendant must show that he reasonably believed that the threatened harm was unlawful.
Fifth, the defendant must show that the threatened harm was of such a nature that it actually required the level of force that the defendant used.
Although these five elements must be proven in any instance in which the defendant claims self defense, one other element must be proven when the defendant has used deadly force on the victim. In such a situation, the defendant must additionally show that he reasonably believed that the other person was about to inflict death or serious bodily harm on him and that the deadly force he used in self defense was necessary to prevent the death or serious bodily harm with which he was threatened. See Beard v. United States, 158 U.S. 550 (1895).
An issue that often comes up when the defendant argues self defense in a deadly force situation, is whether or not the defendant had the duty to retreat before using self defense if, in fact, the defendant had the opportunity to do so. Under the common law, in order for the defendant to use deadly force in a self defense situation, the defendant has to show that he had no opportunity to retreat or that he looked for an opportunity to retreat and could find none.
There are, however, two exceptions to this rule. First, where retreat is required, it is only required where it could have been done in complete safety. That is to say, if the defendant reasonably believed that he could not retreat in complete safety he is not required to retreat at all before resorting to deadly force. See State v. Anderson, 631 A.2d 1149 (Conn. 1993).
The second exception is that retreat is not required of the defendant if the defendant was attacked in his or her own home. See People v. Tomlins, 213 N.Y. 240 (1914).
Many jurisdictions today have abandoned the common law rule and do not have any strict requirements that the defendant retreat before he resorts to the use of deadly force.
Certain unique problems arise in applying the rules of self defense to cases in which the victim is in a long standing abusive relationship (eg. a battered wife), tries to use the self defense argument after she has killed her abuser. The particularly difficult issue arises because of the fact that, in most cases, the victim of the abuse kills the abuser after a particular episode of abuse has ended, and, therefore, any future harm that she fears from her abuser is not imminent. Further, barring any physical confinement that would prevent the abused person from leaving the abuser, the law generally takes the position that the abused victim has other, non-deadly alternatives, other than killing their abusers. It has been advocated, especially in cases where expert testimony shows that the long standing abusive relationship has caused the defendant to think that leaving the relationship is not an option and that further abuse is inevitable, that the law should no longer require the defendant to show that she reasonably believed that the deadly harm she was facing was imminent. Rather, it has been advocated that, in situations like this, it should be enough for the defendant to reasonably believe that the use of deadly force in self defense is necessary to protect herself from deadly force in the future. Some jurisdictions have passed laws to this effect. This defense has become known as the "battered women's syndrome" defense, although it applies equally to children of abusive parents etc.
Typically, the initial aggressor in a fight is not allowed to claim self defense. By beginning the fight, the defendant essentially forfeits his right to use that defense. However, there are two situations in which the initial aggressor will regain the right to use self defense. The first exception is where the defendant has initiated the aggression but has used non deadly force and the victim responds to that non deadly force with deadly force. In this case, even though the defendant was the initial aggressor, he may use whatever force is necessary, including deadly force, to protect himself. The second exception is where the aggressor withdraws from the fight. If the aggressor either physically removes himself from the fight or tells the other person that he no longer wants to fight and the other person continues fighting, the defendant may use whatever force is necessary to defend himself even though he was the initial aggressor.
In some jurisdictions, a person may act in self defense if he is being unlawfully arrested. This is true even where the defendant knows that the person who is arresting him is a law enforcement officer. However, most jurisdictions break from this rule and hold that a person is not allowed to use force in self defense to protect himself from an unlawful arrest if he knows that the arresting party is a law enforcement officer.
Finally, self defense is a complete defense,
meaning that, where it is successfully raised, the defendant will be
acquitted of the crime for which he is being charged. However, where
the defendant is on trial for a homicide, self defense can also act
as an incomplete defense. That is to say, where the defendant successfully
raises self defense in a murder trial, he will win an acquittal. Where
the defendant used force in a situation where he unreasonably believed
that the use of force was necessary to defend himself or in a situation
where he used an unreasonable amount of force, self defense will not
secure an acquittal. However, he may be able to use the defense in an
effort to reduce the charge from murder to a lesser charge of manslaughter.