EXOD768 It is a negative commandment for the court not to accept the testimony of a man of sin for Scripture says, You shall not set your hand with the wicked to be a malicious witness [this verse]. If one qualified witness knows that the other one is wicked while the judges do not recognize his sinfulness, he is forbidden to give testimony with the other – – even true testimony – – on account of the prohibition, You shall not set your hand with the wicked. There is no need to add that if he knows that the second witness is going to give false testimony, he is forbidden to testify with the other.