Evidence to Convict?

[Astreja]

Not adding new "ifs".  The description, that there was no explicit physical evidence which pointed to any particular person was there from the beginning. And it's also the point of the question.

Ah.  What you have there is a straw man -- in the case of a physical assault, there would almost certainly be some physical evidence.  Without a victim or evidence that there was an actual set-to, the police would have nothing to go on and wouldn't be able to file charges.

That does appear to answer your question -- "No, statements of alleged witnesses are in themselves not enough to go on."