2,705. When Only One of Two Witnesses Denies

Hilchos Shevuos 10:13

Let’s say that a plaintiff imposes an oath on witnesses in court and both witnesses deny having information at the same time, meaning that the second witness starts denying immediately after the first has concluded. In such a case, both witnesses are liable for an oath of testimony and each must bring a sin offering. If the first witness denied and the second waited beyond the requisite time and then denied, then the first is liable for an oath of testimony and the second is exempt. This is because even if the second had testified, his testimony would not have been sufficient to make the defendant pay.

Hilchos Shevuos 10:14

If one witness admits to having information and the other denies it, the one who denied is liable regardless of whether he denied before or after the admission of the other witness. If both witnesses denied at the same time, after which one of them immediately admitted to having information, he is exempt while the one who continues to deny is liable for an oath of testimony.