Are you saying that if the police were contracted by victims instead of by society, this would never happen? It seems to me it would just happen more often, as the courts would also be private, and the "victims" could just contract for "Wanted: dead." Non-socialist justice is better known as vigilantism.
It seems that this is how self-defense works in England. It is a
defense against conviction, not a defense against going to court. This sort of conservative attitude ensures that the whole Trayvon Martin vs. George Zimmerman controversy would not happen as the evidence is to be outlined in public in court.
https://en.wikipedia.org/wiki/Self-defence_in_English_law