From: Rabbi Moshe Sofer
To: Avraham Segal
Witnesses who forgot their testimony and later remembered are not disqualified as chozer u'maggid, and their earlier denial is attributed to forgetfulness via ein adam meisim atzmo rasha. An animal with a disputed treifah condition that survives twelve months definitively establishes the halacha for all similar animals, based on the Maharashal and Rashba.
Source: Shu"t Chasam Sofer CM §35