It seems this topic is getting a lot of attention and people feel strongly about it. Since everyone is debating the law, the following is the Penn. Self-Defense statute. It is only the statute so you'll have to find the cases yourselves. Enjoy the debate.
Â§ 505. Use of force in self-protection.
(a) Use of force justifiable for protection of the person.--
The use of force upon or toward another person is justifiable
when the actor believes that...