Reference for Exodus 20:13

Because you shall not bear false witness. Since behold when it is impossible to [punish] the witnesses with "do to them as they planned", for example [they say] "We testify about a certain person [kohen] that he is the son of a divorced woman, the witnesses are lashed due to "you shall not bear false witness". Here [in this case], where there is warning against "you shall not bear false witness" and also "as they planned", they are lashed 80 [times]. The halacha is not like Rabbi Meir.