DEUT1398 Relatives of litigants or people on trial shall not serve as witnesses in court. When two people have litigation in court or someone is on trial for an alleged wrong, the case must be decided on the strength of testimony from witnesses. Therefore, it is important that the testimony be clear, unbiased, true and free of any suspicion. For this reason, the Torah disqualifies testimony from relatives, even when the testimony would be incriminating. If the Torah were to allow courts to accept incriminating testimony from relatives, the courts also might wind up accepting favorable testimony from relatives, and such might lead to a perversion of justice and aroused suspicion about the fairness of the courts’ rulings. The perfect Torah keeps the holy nation away from situations that are potentially harmful, so it entirely bans relatives from giving testimony. An additional benefit is that sometimes, because of constant interaction with one another, relatives quarrel. If courts were allowed to accept testimony from relatives, it would invite cases where, because of his anger, a person seeks vengeance on his relative and in a moment of anger decides to give false testimony against him. This precept of the Torah prevents this.