I'm imagining a very generic situation of violence. Say there are two groups of people, W (witnesses) and A (accused). Some members of group A are accused of an act of violence from all members of group W. All members of group A, whether directly accused or not, deny this accusation.
Apart from this witness testimony, the only other piece of evidence are the injuries sustained by members of group W. However, these injuries are minor enough so that they could be self-inflicted (e.g., torn clothes, a few bruises, or a small flesh-wound cut from a knife).
There is no other evidence. No physical evidence, like a knife or a security camera. Nobody has an alibi either. And there's no good reason for why the supposed violence occurred. The members of W simply claim that it happened and that it was perpetrated by members of A.
The situation is generic, but I think I have described it well enough for one to address it specifically. What happens? With whom does the Law side? How does the answer depend on the sizes of group W and group A?