WHEN CAN WE OVERTURN A VERDICT?
(Mishnah #1): A monetary verdict can be overturned, whether Zechus or Chiyuv:
Contradiction (Mishnah #2): If a judge judged and acquitted the guilty or obligated the innocent, or he declared Tamei what is Tahor or declared Tahor what is Tamei, what he did stands. He must pay for the loss that he caused.
Answer #1 (Rav Yosef): Mishnah #1 refers to a Mumcheh (if he retracts, we are confident that now he is correct). Mishnah #2 discusses a judge who is not Mumcheh.
Question: Do we really overturn the verdict of a Mumcheh?!
(Mishnah): A Mumcheh l'Rabim is exempt (if he erred). (If he can overturn his verdict, there is nothing to pay for!)
Answer #1 (Rav Nachman): A bigger Chacham can overturn the verdict. If there is no bigger Chacham, the verdict stands.
Answer #2 (Rav Sheshes): If he was To'eh bi'Dvar Mishnah (made a clear mistake), we overturn the verdict. If he was To'eh b'Shikul ha'Da'as (ruled unlike the primary opinion), the verdict stands.
Question (Ravina): If he erred in (a Tosefta of) R. Chiya and R. Oshaya, is this considered To'eh bi'Dvar Mishnah?
Answer (Rav Ashi): Yes.
Question (Ravina): Is a mistake about a teaching of Rav and Shmuel included (in To'eh bi'Dvar Mishnah)?
Answer (Rav Ashi): Yes.
Question (Ravina): Is a mistake about one of our teachings included?
Answer (Rav Ashi): Are we loafers?! (Also this is To'eh bi'Dvar Mishnah.)
Question: What is To'eh b'Shikul ha'Da'as?
Answer (Rav Papa): Two Tana'im or Amora'im argue with each other, and the Halachah was not fixed like either one, but the discussion favors one (and the judge ruled like the other opinion).
Question (against Rav Sheshes - Rav Hamnuna - Mishnah): A case occurred in which the womb of a cow was removed. R. Tarfon ruled that it is Treifah, and they fed it to dogs;
Chachamim in Yavneh said that it is Kosher, for they cut the wombs of all cows and pigs that leave Miztrayim (so they will not reproduce, but they live).
R. Tarfon: I will lose my donkey due to my mistake!
R. Akiva: You are Mumcheh l'Rabim; you are exempt.
Summation of question: If we overturn a Ta'us bi'Dvar Mishnah, that is enough to exempt R. Tarfon!
Answer: Indeed, R. Akiva gave a second reason to exempt him:
Since you were To'eh bi'Dvar Mishnah, we overturn the verdict, and you are exempt;
Even if you were To'eh b'Shikul ha'Da'as, since you are a Mumcheh l'Rabim, you would be exempt.
Question (Rav Nachman bar Yitzchak): How could Rav Hamnuna ask from that case. R. Tarfon fed it to dogs, it would not help to overturn the verdict!
Answer (Rava): If regarding To'eh bi'Dvar Mishnah the verdict stands, we understand why R. Tarfon thought that he would be liable;
However, if To'eh bi'Dvar Mishnah can be overturned, why did he expect to be liable? Since if the cow was around his ruling has no effect, even if it is not around, his ruling should have no effect!
Answer #2 (Rav Chisda): If the judge himself transferred the money, the verdict stands. If he did not, we overturn the verdict.
Question: That explains (in Mishnah #2) 'if he obligated the innocent';
Regarding 'he acquitted the guilty' he said 'you are exempt.' He did not transfer money!
Answer #1: Saying 'you are exempt' is like bodily transferring the money.
Question (Mishnah #1): A monetary verdict can be overturned, whether Zechus or Chiyuv:
We understand Chiyuv. Originally, he said 'you are liable' and did not transfer the money himself, and later he retracted;
However, if saying 'you are exempt' is like bodily transferring the money, this can never be retracted!
Answer: Mishnah #1 means that a monetary verdict of Chiyuv can be overturned, even though this is Zechus for the other party (but a verdict of 'exempt' cannot be overturned).
Inference: The Mishnah says that in capital cases we can overturn a verdict of Chiyuv, but not of Zechus. I.e., we can change to Zechus only if it does not harm anyone else (e.g. Ploni was sentenced for Chilul Shabbos).
Question: Who could be harmed if Ploni is exempted?
Answer: (In a murder case,) the Go'el ha'Dam (the relative of the victim) is harmed (he hoped to avenge the murder).
Objection #1: Will we kill Ploni due to (not wanting to retract, lest this upset) the Go'el ha'Dam?!
Objection #2: The Mishnah says that a monetary verdict can be overturned, whether Zechus or Chiyuv!
These questions are left difficult.
Answer #2 (to Question (e) - Ravina): Almoni had a security of Ploni. When the judge exempted Ploni, he took the security and gave it to Ploni.
'He declared Tamei what is Tahor' can also be through the judge's action. He touched a Sheretz to it to 'prove' that it is Tamei;
Regarding 'he declared Tahor what is Tamei', the judge mixed it with other Taharos of Ploni to 'prove' that it is Tahor.
CHANGING THE VERDICT
(Mishnah): In capital cases (we can overturn a verdict of Chiyuv, but not of Zechus).
(Beraisa) Question: What is the source that if Beis Din sentenced Ploni to die, and someone had a reason for Zechus, that we return him and reconsider the verdict?
Answer: "V'Naki (v'Tzadik) Al Taharog."
Question: What is the source that if Beis Din acquitted Ploni, and someone had a reason for Chiyuv, that we do not reconsider the verdict?
Answer: "V'Tzadik Al Taharog."
(Rav Simi bar Ashi): The opposite applies to a Mesis (we return to convict, but not to acquit) - "v'Lo Sachmol v'Lo Sechaseh Alav."
(Rav Kahana): We learn from "Ki Harog Tahargenu."
Question (R. Zeira): What is the source that the same applies to someone sentenced or exempted from Galus (for killing unintentionally, and we overturn only a verdict of Chiyuv)?
Answer (Rav Sheshes): We learn from a Gezerah Shavah "Rotze'ach-Rotze'ach."
Question (R. Zeira): What is the source for (conviction or exemption from) lashes?
Answer (Rav Sheshes): We learn from a Gezerah Shavah "Rasha-Rasha."
Support (Beraisa): We learn Chayavei Galuyos from "Rotze'ach-Rotze'ach." We learn Chayavei Malkos from "Rasha-Rasha."
(Mishnah): We do not overturn a verdict of Zechus.
(R. Chiya bar Aba citing R. Yochanan): This refers to a mistake about something that the Tzedukim (who reject our Oral tradition) do not agree to. Something that even they agree to is a blatant error, and we overturn it.
Question (R. Chiya bar Aba): If they exempted adulterers, what is the law?
Answer (R. Yochanan): You can answer that from what you already know. (Tzedukim admit to this.)
(R. Ami): If they exempted adulterers, we overturn this.
Question: What is a case (of adultery) that we do not overturn? (The Mishnah said that in capital cases, we do not overturn a verdict of Zechus, without specifying. This implies that this applies (at least sometimes) to every capital transgression.)
Answer: They exempted them for abnormal Bi'ah.
ARGUING FOR ZECHUS
(Mishnah): In monetary cases, anyone can give a reason for Zechus or Chiyuv... (in capital cases, anyone can give a reason for Zechus, but not everyone can give a reason for Chiyuv).
Inference: Anyone includes the witnesses.
Suggestion: Our Mishnah is like R. Yosi b'Rebbi Yehudah, and unlike Chachamim.
(Beraisa): "V'Ed Echad Lo Ya'aneh v'Nefesh" - a witness in a capital case cannot argue (at all, not) for Zechus or Chiyuv.
R. Yosi b'Rebbi Yehudah says, he can speak for Zechus, but not for Chiyuv.
Answer (Rav Papa): No, anyone includes the Talmidim. All agree to the Mishnah.