In Pennsylvania, when a person claims self-defense, they are admit committing a crime but they are providing a defense as to why it was necessary. A successful self-defense claim will completely excuse the actor for committing the crime. To successfully claim self-defense, three things are necessary:
The actor must reasonably believe that he was in imminent danger of death, serious bodily injury, kidnapping, or rape.
The actor's belief that force is necessary must be a “reasonable belief” in light of the facts as they appeared to the actor at the time of the crime. If the actor really did believe that force was necessary, but his belief was unreasonable, he may have a self-defense claim that is “imperfect.” This “imperfect” defense may protect the actor from being convicted of the highest offense, such as first-degree murder, but will probably result in his conviction for a lower offense, such as voluntary manslaughter.
The actor must have used only a reasonable amount of force, or the amount of force necessary to repel the attack.
In general, when the force being used by the attacker is non-deadly, the actor can retaliate with equal force without having to retreat. However, when an attacker is using deadly force, states vary as to when and under what circumstances the target of the attacker has a duty to retreat. In some states, deadly force cannot be used when the actor can safely retreat from the attacker. In Pennsylvania, an actor may use deadly force to retaliate when he is threatened by someone using a firearm or other lethal weapon, even if he is able to safely retreat from the situation. Additionally, in Pennsylvania, you have no duty to retreat from your own home and may use deadly force against anyone who attacks you while in your own dwelling if the force used to retaliate was excessive, malice could be proven and a claim of self-defense would not be available. For example, if the actor shoots the attacker more times than is necessary, or an actor retaliates against the attacker by using a gun when the attacker was only using his fists, the actor has used excessive force and may be found guilty of acting with malice, or wrongful intention.
The actor must not have provoked or continued the situation resulting in the force being used.
This requirement of self-defense was at issue in the Trayvon Martin case. It was debated as to whether George Zimmerman would be able to claim self-defense because it was thought that he may have provoked or created the situation requiring him to use force. When an actor brings about a fight and then later feels the need to defend himself from the person he provoked, he is unable to claim self-defense.