Deuteronomy 19:15-21 - Laws Concerning Witnesses
15 One witness is not enough to convict someone of a crime, offense, or sin he may have committed. Cases must be settled based on the testimony of two or three witnesses.
16 This is what you must do whenever a witness takes the stand to accuse a person falsely of a crime. 17 The two people involved must stand in Jehovah's presence, in front of the priests and judges who are serving at that time. 18 The judges must make a thorough investigation. If it is found that the witness lied when he testified against the other Israelite, 19 do to him what he planned to do to the other person. Get rid of this evil. 20 When other people hear about this, they will be afraid. Never again will such an evil thing be done among you. 21 Have no pity on him: Take a life for a life, an eye for an eye, a tooth for a tooth, a hand for a hand, and a foot for a foot.