What is self-defense? It's a good defense for a crime if you had to fight back to protect yourself from being injured. It's accepted in most cases that people who are under threat will fight back and potentially even break laws to keep themselves safe. As a defense option in court, self-defense can be used to show why someone would attack, hurt or kill another person.
A self-defense claim can help a jury and judge understand why a typically non-violent person would suddenly be involved in a violent act. To prove self-defense, it's important to know that you must have had a sufficient reason to react in the manner you did. For instance, if someone kicks you, it may not be a good enough reason to kill him or her. However, if someone has a gun and has shot at you before you attack with a knife, then you could say it was a reasonable response to an imminent threat.
Offensive words themselves are not enough to constitute as an imminent threat. That means that if someone is just being aggressive but hasn't been violent, there is little way to use self-defense as a claim if you attack the other person. Your fear of harm must be reasonable, so if there was no real risk of harm, then you could be held accountable for your actions against the other person.
When you're in a situation where you need to use self-defense as a claim to defend yourself against charges, your attorney may have you collect evidence like videos or photographs. Information on your medical treatment following an attack may also help prove your innocence.
Source: FindLaw, "Self-Defense Overview," accessed Nov. 04, 2015