Deuteronomy 19:15-21

One witness shall not rise up against a man for any iniquity, or for any sin, in any sin that he sinneth: at the mouth of two witnesses, or at the mouth of three witnesses, shall a matter be established. If an unrighteous witness rise up against any man to testify against him of wrong-doing, then both the men, between whom the controversy is, shall stand before Jehovah, before the priests and the judges that shall be in those days; and the judges shall make diligent inquisition: and, behold, if the witness be a false witness, and have testified falsely against his brother; then shall ye do unto him, as he had thought to do unto his brother: so shalt thou put away the evil from the midst of thee. And those that remain shall hear, and fear, and shall henceforth commit no more any such evil in the midst of thee. And thine eyes shall not pity; life shall go for life, eye for eye, tooth for tooth, hand for hand, foot for foot.