Deut 19:16-21

16If a malicious witness comes forward to accuse someone of wrongdoing,17then both parties to the dispute shall appear before the Lord, before the priests and the judges who are in office in those days,18and the judges shall make a thorough inquiry. If the witness is a false witness, having testified falsely against another,19then you shall do to the false witness just as the false witness had meant to do to the other. So you shall purge the evil from your midst.20The rest shall hear and be afraid, and a crime such as this shall never again be committed among you.21Show no pity: life for life, eye for eye, tooth for tooth, hand for hand, foot for foot.