Diablery evidence or your word versus theirs?

OK, what happens in situations like these.

Vampire A goes missing. Vampire B was the last person seen with them. Vampire B is then seen with black stains in their aura by someone with Auspex. Vampire B told their clannmates that they got rid of the problem Vampire A, but not how.

What happens? It's all circumstantial evidence, but is someone seeing black stains in your aura enough to accuse them or is it more your word against theirs?