First of all, there is no such thing as "proof." Parties present evidence to courts, and that evidence may take the form of personal testimony. My guess is that you're dealing with a situation where a judge is accepting certain evidence without corroboration of some sort. However, corroboration is rarely required. Therefore, if the testimony is uncontradicted and there are no issues about the witness's credibility, then there'd be no reason not to accept it. If the evidence is contradicted by someone else's testimony, then the judge has to decide who is more believable. Absent some facts or context, I can't say more than that and that you should consult with your attorney.
