[If] others came and they discredited them, [and still] others came, and they discredited them [too], even one hundred, all of them are executed. R' Yehudah says: This is a group of plotters, and only the first group is executed.

Zomemim witnesses are not executed unless the verdict has been delivered. For the Sadducees say: Unless he had been exe-cuted, as it is said: A life for a life. The Sages said to them: Has it not already stated (Deut. 19:21): And you shall do to him as he planned to do to his brother —- indicating that his brother is still alive! If so, why does it say, A life for a life? Because it might be thought that from the time their testimony is ac-cepted, they may be executed; [the Torah] therefore states: A life for a life —- [to teach] that they are not executed unless a verdict has been issued.