Can a party in a case ever argue that their opponents' lay witness lacks credibility just because there is no evidence of their credibility?
Where the judge is the trier of fact (judge-alone/bench trials), can they assert that a witness is not to be trusted simply as there is no evidence of their character?
To avoid doubt, there is no evidence discrediting the witness.
(Any common law jurisdiction).
Background to the question
Unlike the police, private prosecutors cannot access criminal history of their witnesses to disclose to the defence. The defence, having been used to be given criminal histories of prosecution witnesses, questions credibility of the private prosecutor's witnesses and challenges the prosecutor to ask the witnesses to disclose their criminal histories voluntarily. The judge says that refusal to do so may be seen as a doubt of credibility of the witnesses. I say that is arguable, to which the judge agrees. It is unclear how this would be ultimately resolved.