From: Rabbi Moshe Sofer
To: Rabbi Shemarya
The Chasam Sofer analyzes Rabbeinu Hai Gaon's novel position that hazamah (witness impeachment) is only complete when the impeached witnesses admit or remain silent, while active denial renders the encounter mere hakchashah. He identifies a textual variant in the Mishnah in Makkos as the basis for this view and shows how it resolves several difficulties, but raises four strong objections that leave the position marked as requiring further investigation.
Source: Shu"t Chasam Sofer CM §141