Eidim zomemin

Eidim Zomemin (false witnesses) is a case in the gemara in Masechta Makkos in which witnesses are proven to be false by the testimony of two or more other witnesses who say "It is impossible for you to have witnessed "Ploni" committing such and such crime in such and such place at such and such time as you were with us in another place at that time." The two original witnesses are then given the sentence that would have been exacted on the person they were "testifying" on.