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.

  • Let's take My Cousin Vinnie as an example: there is the old lady that claims to have seen the two. The defense lawyer claims she isn't credible, but he doesn't make the whole show about her no being able to see the number of fingers lifted even with her glasses?
    – Trish
    Sep 26, 2021 at 20:15
  • @Trish I know that scene but I don't get your point. Clearly what Vinny does is discredit her: she can't see how many fingers he is holding up despite half the distance. Conversely, in this question there is no evidence discrediting the witness.
    – Greendrake
    Sep 26, 2021 at 20:22
  • So your fivtive lawyer just claims "This wittness is not credible" but shows not why, yes?
    – Trish
    Sep 26, 2021 at 20:31
  • @Trish That's exactly right. See updated question for details.
    – Greendrake
    Sep 26, 2021 at 20:36
  • 1
    I thought witness credibility was always up to the finder of fact to decide, based on the testimony itself as well as whatever other evidence may or may not be offered. I've never heard of any rules defining situations where the finder of fact must, or must not, consider a witness as credible. Sep 26, 2021 at 21:40

2 Answers 2


If anything, the opposite. A witness under oath is assumed to be testifying truthfully in the absence of evidence to the contrary. A jury, of course, is free to weigh the credibility of a witness in any manner desired.


A lawyer for either party can claim, during argument, that an adverse witness is not credible, for any reason or none. Often the lawyer will point to matters disclosed during cross-examination, claiming that they are contradictions, show bias, or otherwise indicate lack of credibility. Or the lawyer could point to elements of the primary testimony which the lawyer claims are implausible. If there has be evidence of a prior conviction, the lawyer could refer to this. A lawyer may in general ask a witness about prior convictions.

Criminal convictions are generally matters of public record, and can be researched.

It is not usual to present reputation or credibility witnesses for any person except the defendant, and failure to do so, even for the defendant, does not lead to any automatic assumption of lack of credibility. Not does the appearance of such a witness grant an automatic assumption of credibility. But a lawyer may point out reasons for thinking a witness not credible.

Ultimately it is up to the finder of fact, often a jury, to decide what weight to give the testimony of each and every witness, based on the impression that testimony made, as well as any argument from the lawyer. This is one reason why courts are reluctant to overturn factual assessments by a jury: the reviewing court does not see and hear the manner of a witness and what it may indicate about credibility.

  • "Criminal convictions are generally matters of public record, and can be researched" — where is that? Of course you can find published judgments, but, in general, I am not aware of any way for the public to check convictions of a given person without their consent.
    – Greendrake
    Sep 26, 2021 at 22:45
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    Most jurisdictions in the US now provide this info online. There are now a number of firms that will, for a small fee, search all public records including criminal for a specified person. They advertise this as a way to check up on dates and potential business partners. It never required the consent of the subject to check criminal records, but it used to be tedious because one had to check jurisdictions one-by-one. Now this has been automated. Sep 26, 2021 at 23:27
  • @Greendrake [...] Also, there is such a thing as discovery in a criminal case in many places, where a witness could be asked about prior convictions. Sep 26, 2021 at 23:32
  • Wow, it pretty much surprises me that in the US you can check convictions without subject's consent. In New Zealand this info is protected by privacy laws. Also, discovery/disclosure requires the prosecutor to provide only what he has hands-on access to; if inquiries need to be made to retrieve info, then it does not need to be done.
    – Greendrake
    Sep 27, 2021 at 0:43
  • 1
    @Greendrake Records of convictions have always been public in the US, right back to the colonial period. After all they are delivered in open court, and anyone may record them there. Arrest records are public too. Employers can and do check them. If a witness is deposed during during discovery, s/he can be asked about prior convictions then. Sep 27, 2021 at 15:42

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