Commentary for Deuteronomy 19:16

לענות בו סרה [IF A WITNESS FOR VIOLENCE RISE UP AGAINST A MAN] TO TESTIFY AGAINST HIM סרה — i.e. a thing which does not exist at all; this term is used because this witness is far removed (הוסר) from having anything to do with this testimony. How is this? (Give an example of such a case)?! That two other witnesses say, “But were you not with us on that day (when you say you saw the defendant committing this crime) in such and such a place (different from that where the alleged crime, according to you, has taken place)?!” (Makkot 5a).

כי יקום עד חמס באיש, “If a false witness stands up against a man, etc.;” whenever the Torah speaks of עד without identifying the number of witnesses, 2 witnesses are meant. The meaning of our verse is that if two false witnesses testify against someone, i.e. claiming that something had been done which had never occurred that is the meaning of the word סרה, i.e. the witness is removed, הוסר, from such testimony. For instance, if two witnesses confront the original witnesses saying “how could you testify to an occurrence in such and such a place on such and such a date when in fact you were in our company on that date in a totally different place?” (Makkot 5)

As the witness was dissociated from the entire testimony, etc. This is not the case where two [sets of] witnesses merely contradict each other, because each agrees that the other was present at the incident, except that one says that the incident was like this and the other says it was like that. Regarding conspiring witnesses however, the witness is disassociated from his entire testimony, because these witnesses say, “You were with us and you were not present at that incident.”