Gemara

(Mishnah): If witnesses testify that Ploni is a Chalal (Pasul Kohen), we do not say that each witness becomes a Chalal. Rather, he is lashed.

(R. Yehoshua ben Levi): "Va'Asisem Lo Ka'asher Zamam" - to him, not to his descendants. (If the witness would become a Chalal, this would disqualify his descendants).

Question: He should be a Chalal, and his children will be Kesherim!

Answer: This is not "Ka'asher Zamam." (He plotted to disqualify Ploni and Ploni's descendants).

Sanhedrin 9b (Rav Yosef): If Reuven brought witnesses that his Kalah was Mezanah, and her father (David) brought witnesses who were Mezim them, Reuven's witnesses are killed, but they do not pay (even though their testimony would also have deprived her of her Kesuvah);

If Reuven brought witnesses who were Mezim David's witnesses, David's witnesses are killed, for they tried to kill Reuven's witnesses. They also pay, because they tried to cause obligate someone else (Reuven) to pay (a fine).

Krisus 24a (Rav Kruspedai): If witnesses testified that an ox must be stoned due to bestiality and they were Huzmu, it is Hefker (the owner despaired).

Rishonim

Rambam (Hilchos Edus 20:8): If witnesses testified to convict a Rasha who is not lashed and does not pay money, and they were Huzam, they are lashed. E.g., they testified that a Kohen is a Ben Gerushah, or that Ploni killed b'Shogeg, or that his ox gored, or that he was sold to be an Eved Ivri. A tradition from Sinai teaches that they are lashed.

Ran (Sanhedrin 9b DH R.Tam): The Gemara connotes that if one is Chayav Misah for what he did to David and owes money to Levi for something he did at the same time, he is killed and pays. R.Tam says that this applies only to Edim Zomemim, for if they would not pay, the monetary testimony would be Iy Efshar Lehazimah. The husband's witnesses do not pay because their mortal and monetary liabilities are to the same person (the Kalah). The primary (capital) testimony can be Huzam, therefore we do not Mevatel the monetary part of the testimony that cannot be Huzam. Normally, one does not pay, like we learn from Demei Vlados (one does not pay for causing a miscarriage if he killed someone else at the time).

Question: Why do we say that the witnesses pay and are killed? We should say that the monetary testimony is Iy Efshar Lehazimah, and it is invalid!

Answer (Ran): Rav Yosef teaches that normally Kam Lei bid'Rabah Minei (one who is killed does not receive another punishment), but Edim Zomemim pay and are killed. We learn from Ka'asher Zomam. However, when both liabilities are to one person, we fulfill Ka'asher Zomam through death alone (for the Nidon himself would not have paid, due to Kam Lei bid'Rabah Minei).

Ohr Some'ach (Hilchos Sanhedrin 13:7): If witnesses testified that a married woman was Mezanah, if they were Huzmu, they would be killed. They would not pay for trying to make her forfeit her Kesuvah, due to Kam Lei bid'Rabah Minei. We do not say that they cannot deprive her of her Kesuvah because it is Iy Efshar Lehazimah, since the loss of her Kesuvah is a mere result of their testimony. Tosfos (Sotah 25b DH Beis) asks why a Sotah whose husband died before she drank does not receive her Kesuvah. He assumes that her husband owes a Kesuvah, unless she forfeited it. Perhaps the Chiyuv to pay a Kesuvah is only if she will be faithful. If so, testimony to forfeit her Kesuvah need not be Efshar Lehazimah. Since she became forbidden, she loses it automatically.

Question (Tosfos Makos 2a DH Me'idin): A witness cannot become a Ben Grushah (a Chalal) through Hazamah. This is Iy Efshar Lehazimah!

Answers (Tosfos): Being a Chalal entails only Lavim. Since the witnesses are lashed, this is called Efshar Lehazimah. Alternatively, the Torah does not require Efshar Lehazimah for such testimony.

Tosfos (Bava Kama 4b DH v'Edim): The Riva says that Ka'asher Zomam v'Lo Ka'asher Osah (we do not kill Edim Zomemim if the Nidon was killed) does not apply to money (they pay even if the Nidon already paid).

R. Akiva Eiger (1:176): All agree that the Torah requires Efshar Lehazimah for monetary cases. The argument is whether or not Chachamim uprooted this when they enacted that monetary cases do not need Drishah v'Chakirah. In Bava Kama 88a, Rashi says that a minor is Pasul for testimony because it is Iy Efshar Lehazimah, for he cannot be punished. In Bava Basra 155b, the Gemara learns only from "the two men will stand." Why did it omit the second reason? In Bava Kama, the Gemara sought to learn that a slave is Pasul from a Kal va'Chomer. The Sugya discusses the law mid'Oraisa. In Bava Basra, the Gemara teaches that a minor is Pasul even mid'Rabanan. After Chachamim enacted not to require Drishah v'Chakirah, we do not need Efshar Lehazimah. Rashi is difficult. If the only reason a minor is Pasul is because Iy Efshar Lehazimah, he is not intrinsically Pasul. Also an adult's testimony is invalid if it is Iy Efshar Lehazimah! I would explain that "the two men" excludes minors. According to one answer in Tosfos, this is needed for testimonies such a Ben Gerushah, which does not require Efshar Lehazimah. According to the other answer, lashes fulfill Ka'asher Zomam. A minor cannot be lashed! However, the verse must teach that minors cannot contradict witnesses. If two said that Ploni killed, and two contradict them, Ka'asher Zomam does not apply to the latter witnesses. They did not seek to obligate anyone! They are not even lashed for "Lo Sa'aneh b'Re'echa", for they did not testify against anyone. Minors cannot testify even about the new moon, to which Ka'asher Zomam does not apply. Also, since he is intrinsically Pasul, he cannot testify when he matures about what he saw when he was a minor, even though now it is Efshar Lehazimah.

Nimukei Yosef (Bava Basra 30a DH Masnisin): Why do Edim Zomemim who testified about a Chazakah pay? Once we accepted their testimony, the claimant received the land. We should say v'Lo Ka'asher Osah! The Ritva answered that the claimant was not on the land at the time.

Question: If the Nimukei Yosef holds that v'Lo Ka'asher Osah applies also to money, Edim Zomemim would not pay for false testimony to stone an ox. Once there was a final verdict, the ox is Hefker, and the owner already lost. If so, the testimony is Iy Efshar Lehazimah. How do we stone an ox? Even those who do not require Efshar Lehazimah for monetary cases require it here, for "v'Gam Ba'alav Yomas" equates killing an ox to killing a person.

Answer (the questioner in R. Akiva Eiger): We must say that the ox does not become Hefker. Krisos 24a said so only regarding bestiality. It does not require Efshar Lehazimah, for it need not be killed like a person. It is a regular monetary case.

Rebuttal (R. Akiva Eiger): Mid'Oraisa, also monetary cases require Efshar Lehazimah! Tosfos holds that we do not say v'Lo Ka'asher Osah in monetary cases. And even if the witnesses do not pay, they are lashed. V'Lo Ka'asher Osah does not apply to Lo Sa'aneh. Therefore, it is considered Efshar Lehazimah. If we would not say so, how can witnesses testify about Chazakah according to the opinion that requires Efshar Lehazimah even after Chachamim uprooted Drishah v'Chakirah? If the Machazik is in the land, the moment the testimony was accepted, the owner lost! Also regarding an ox, we must say that v'Lo Ka'asher Osah does not apply to money, or they are lashed. Surely, we do not need Efshar Lehazimah for death of an ox, for it can never be fulfilled. Also, Ka'asher Zomam La'asos l'Achiv does not apply.