- Reversing a ruling: טעה בדבר משנה - גדול הימנו בחכמה ובמנין vs. טעה בשיקול הדעת
The Mishnah taught that verdicts in דיני ממונות can be reversed in either direction. This contradicts a Mishnah in בכורות which states: דן את הדין – if one ruled on a case, זיכה את החייב – and he mistakenly ruled the liable party exempt, or the exempt party liable, or he ruled tamei that which was actually tahor, or the opposite, מה שעשה עשוי וישלם מביתו – what he did is done, and he must repay the damaged party from his property. This proves a decision is not reversed!? Rav Nachman answers that our Mishnah refers to a judge who is גדול הימנו בחכמה ובמנין – greater than [the first] in wisdom and number and can reverse the first decision. Rav Sheishess answers that our Mishnah’s case is שטעה בדבר משנה – where [the judge] erred in something taught by a Mishnah; such a blatantly mistaken verdict is reversed. The other Mishnah is שטעה בשיקול הדעת – where he erred in judgement, which is not reversed. Rav Ashi told Ravina that "טעה בדבר משנה" includes rulings of Baraisos, Rav and Shmuel, and even their own. An error of "שיקול הדעת" is defined as a machlokes between Tannaim or Amoraim, without an established halachah, and the judge ruled against the opinion that most judges follow.
- נטל ונתן ביד
Rav Chisda answered that the Mishnah in בכורות is שנטל ונתן ביד – where [the judge] took the payment from one party and gave it by hand to the other party. A verdict executed by the judge, albeit erroneous, cannot be reversed. Our Mishnah is where the judge did not carry out the mistaken verdict, so it can be reversed. The Gemara asks that the second case of that Mishnah, זיכה את החייב – where he ruled the liable party exempt, is completed by the mere verbal ruling, with no physical action!? The Gemara first answers that the verdict of exemption itself is tantamount to physically taking the money from the claimant and handing it to the defendant. However, this interpretation is found difficult because of our Mishnah. Ravina explains that the physical action in the second case can be where the claimant had a משכון for the debt, and the judge took it and returned it to the defendant. The third case of that Mishnah, where he ruled something tahor as tamei, is where he touched a sheretz to the food in question (rendering it definitely tamei in accordance with his mistaken ruling). The fourth case, where he ruled something tamei as tahor, is where he then mixed the food in question into other tahor food.
- דיני נפשות are only retracted לזכות, not לחובה
A Baraisa sources the Mishnah’s ruling, that if one was convicted for the death penalty, and someone said, "יש לי ללמד עליו זכות" – “I have what to argue in favor of his acquittal,” we return him to Beis Din to hear the argument, because the passuk says: נקי אל תהרג – do not kill an “innocent” person (i.e., one who was initially convicted). However, if one was acquitted, and someone said, “I have an argument to convict him,” we do not return him to hear the argument, because the passuk says: צדיק אל תהרג – do not kill a “righteous” person, meaning someone initially found righteous. Rav Shimi bar Ashi says the reverse applies to a מסית (i.e., we would reconsider an innocent verdict, but not a guilty verdict).
The Gemara adds that a verdict of גלות or malkus is also reversed for acquittal only.
Rebbe Yochanan said that erroneous acquittals are only not reversed if the mistake was בדבר שאין הצדוקין מודין בו – regarding something to which the צדוקים do not concede, but a mistake so obvious that even the צדוקים agree with us, זיל קרי בי רב הוא – it is something one can go read in school, and the verdict is overturned.