Originally Posted by After Shock Media

Reason is that the police have no real idea what really started the fight or if you did not have prior issues and so forth. That is not their jobs. They must just try to get a story and piece it together then make a choice. Depends on whom the believe and such.

As also stated above, even in a case of self defense or mutual combat. If one person is seriously hurt or killed. You very well can be charged with anything from manslaughter to murder. Self defense is tricky at best. You are only allowed to use reasonable force in order to escape and no more.