Our Gemara tells a fascinating story. In Rava’s courtroom a woman appeared who was obligated to take an oath. (It should be noted that in Jewish courts the obligation to take an oath does not rest on witnesses, who are assumed to be reliable unless we know otherwise, rather the defendant may be called upon to swear that he does not owe money, for example, if there was only a single witness against him.) Rava’s wife, who was Rav Ḥisda’s daughter, informed him that she knew the woman to be unreliable. Based on that information, Rava did not allow her to take an oath, but asked the other party to take the oath instead. Hipukh shevuah – switching the oath to the other party – is not an unusual ruling. In all cases where one party cannot take the oath (swearing that he owes no money), the shevuah is switched to the plaintiff who will be asked to swear that the money is really owed to him.
Subsequently, a promissory note was brought into Rava’s courtroom with a request that the court obligate the borrower to pay. Rav Pappa stated that he had personal knowledge that this note had already been paid. Once Rava ascertained that there were no other witnesses and that Rav Pappa was the only one who could testify, he rejected Rav Pappa’s testimony, arguing that a single witness could not be accepted in court. Rav Adda bar Mattana objected that Rava had accepted his wife’s statement with no compunctions! In response, Rava explained that he trusted his wife implicitly, and knew with certainty that she would never lie. With regard to Rav Pappa, however, he could only follow the letter of the law, which required two witnesses.
This story is the source for the Rambam’s ruling (see Hilkhot Sanhedrin 24:1) that with regard to cases dealing with money, a judge has the right and the responsibility to rule according to his understanding of the case, even if all of the legal requirements with regard to testimony have not been fully met. Nevertheless, the Rambam continues (see Hilkhot Sanhedrin 24:2), even though this is the halakha, due to concerns with unreliable courts, we no longer practice this rule. Thus, if a judge believes that the witnesses before him are offering false testimony, if he is unsuccessful in disproving them, his only choice is to recuse himself and allow another judge to rule.