Unlike modern courtrooms, where witnesses are asked to swear prior to their testimony in order to ensure that they will tell the truth, a Jewish courtroom believes that every witness who is called to testify will tell the truth. Nevertheless, there are several types of people, enumerated in the Mishnayot of Massekhet Sanhedrin, who cannot testify. Close relatives, for example, cannot testify, no matter how upstanding and honest we know them to be. There are also people whose behavior does not allow the court to accept them. Among them are untrustworthy people who have committed sins that put them in the Biblical category of a rasha. While the people discussed in this Mishna have not done anything that the Torah forbids, nevertheless, their participation in activities that show them to be susceptible to the influence of monetary gain makes us fear that they could be bribed or similarly influenced to change their testimony.
The Mishna on our daf teaches that a father and son who witness the new moon should both come to court, for even though they cannot testify together, if one of them is disqualified from testifying, the other one will be able to join with someone else who saw the moon and be accepted with him as witnesses.
Our daf also quotes in full a Mishna that appears in Massekhet Sanhedrin (24b) that lists people who will not be accepted as witnesses in a Jewish court, because they are involved in monetary shenanigans that are forbidden by the Sages. These people include dice players, money lenders who take interest, people who gamble on pigeon races, and those who market produce from the Sabbatical year. Nevertheless, Rabbi Yehuda teaches: ba-meh devarim amurim – “under what circumstances is this rule taught” – when this is their livelihood. If a person has another occupation and participates in these activities only occasionally, then he can still be trusted as a witness in court.