Disinterested witness is a witness who has no private interest in the lawsuit and has no stakes in the outcome of the case to which she offers evidence.
In criminal and civil cases, if a witness has a personal interest in the case, the witness’s credibility is taken as a question of fact and must go to the jury. That a witness is involved in the case to some degree does not automatically disprove one’s testimony, but the jury must weigh the testimony in light of specific circumstances.
When evaluating the credibility of the evidence, the court should not give more weight to the evidence presented by a disinterested witness than that of an interested witness. The court should not also instruct the jury to disregard or give little consideration to the witness’s testimony where the witness has an interest in the case. Further, the court should not comment on the evidence by stating or implying that a certain witness is interested or disinterested.
On a motion for judgment as a matter of law, under the Federal Rules of Civil Procedure the court should consider the uncontradicted testimony by a disinterested witness that favors the moving party. The court should not grant a motion if the testimony is given by a witness with a personal interest in the case, even if the testimony is uncontradicted, unless the truth of the testimony is corroborated by other evidence.
[Last updated in June of 2020 by the Wex Definitions Team]