There is no such crime as "domestic violence". Rather, the term, and the legal concept behind it, is a modifier to existing crimes. Hitting somebody (a third degree assault) is one thing. However a third degree assault on a person with whom the accused has "an intimate relationship" is "domestic violence". All sorts of procedural and sentencing repercussions flow from this labeling, but the fact remains: you must first have a crime. Further, all the affirmative defenses applicable to a given crime, e.g. self-defense for assaults, apply just as much as they do in non-domestic incidents.

If you are accused of domestic violence it is important you know that notwithstanding all the hubub of victims’ advocates, media focus, District Attorneys’ political considerations, and the court-fed therapeutic industry, you are not guilty of domestic violence if you are not guilty of the crime with which you’ve been charged. Judges understand this, and juries can be made to understand it.