חושן משפט ל"ד 4

24. If they testified about someone that he violated a specific sin, even though he did not receive a warning and therefore does not receive lashes, that individual is disqualified from testifying. This is true where he violated a sin that all of the Jews know is a sin. If, however, they saw him commit a sin on something that is close to a mistake, they must warn him first and then disqualify him. How so? If they saw him tying or untying on Shabbos they must inform him that this is a desecration of Shabbos because most people don’t know this. Similarly, if they saw him doing work on Shabbos or Yom Tov, they must tell him that it is Shabbos because he may have forgotten. Similarly, one who consistently plays with stones or becomes a tax collector or a collector that adds for himself, the witnesses must inform him that anyone that does this is disqualified from testifying because most people don’t know these things. The same applies to anything similar.

25. A person cannot disqualify himself due to sin. Rather, witnesses must testify against him because a person cannot establish himself as wicked. Nevertheless, we would not make him a witness in the first instance as is discussed later in 92:5. Similarly, we do not disqualify based on a rumor or mere suspicion such as where someone is suspect in the area of immoral relations because he often secludes himself with forbidden relations and rumors have spread. Such a person is valid for all testimony with exception of testimony for a woman. For the laws of those that are suspected, see Yoreh Deah Siman 119.

26. If a borrower testified against a lender that he lent him with interest and the borrower has another witness join with him to disqualify the lender, although a person cannot establish himself as wicked, we can split his words and we believe him with respect to the lender but not with respect to himself. Similarly, if he testifies that so and so had sexual relations with him- even if consensual, or he testifies that so and so had sexual relations with his wife or animal, he and another person may join together and testify to disqualify him. The same applies with respect to a theft victim who may testify against the thief just like a borrower can testify against the lender, so long as he gets no gain out of his testimony.

27. There are those that say that where one takes an oath to contradict a solo witness, that witness and the party that was the recipient of the oath may join together to disqualify the person that took the oath. The same applies if he took an oath to two counterparties, and they can testify against him to disqualify him. There is no distinction whether he swore to both in one oath or one after the other. There are those that disagree and hold that even if there were two counterparties who each had their own witness, they would not be able to join together once he stood in judgement and he swore on the testimony. Prior to this, however, they are able to testify against him.