Is there any case law in which a witness has not been sworn?

In Slauter v. Whitelock, 12 Ind. 338, one of the grounds of the attack on a verdict for the plaintiff was that one of the witnesses had not been sworn. We are not informed, says the court, when the mistake as to the testimony having been without the sanction of an oath was discovered by the complaining party. The first we hear of it is in the reasons for a new trial. If it was known before the jury retired, the mistake could have been corrected by swearing the witness and rehearing the evidence, or if that course was not taken, by an instruction to the jury to disregard his statements. If no motion was made upon the discovery, by either party, it would amount to acquiescence in the reception of his statements as evidence in the case.

The case of Hawks v. Baker, 6 Greenl. (Me.) 72, 19 Am. Dec. 191, was one in which an unsworn witness testified, believing that he had been sworn, and in which the omission to administer the oath [184 N.Y. 308]was unknown to the parties or their counsel until after the verdict. Here, of course, there was no room for the application of the doctrine of waiver, and the verdict was set aside; but the court in granting a new trial, distinctly recognized the fact that a party might by implication consent to the reception of testimony by a witness who had not been sworn, saying: It is a well settled principle of law that no evidence can be permitted to go to the jury, unless under oath, without express or implied consent.