Reb Chaim, very nice to hear from you!

See Teshuvos Ben Porat 1:8 (p. 68, DH v'Hineh, in a Teshuvah to Rav Pinchas Menachem of Gur, the author of Sifsei Tzadik), and see Asvon d'Oraisa Klal 16 (p. 106, DH v'Al Ken Nir'eh).

1) The Asvon d'Oraisa, in Klal 16, discusses how we define what a Tereifah is. Before I saw the Asvon d'Oraisa I always thought that a Neveilah is a healthy animal which was not slaughtered properly and therefore is both forbidden to eat and also makes Tamei anyone who touches it. A Tereifah is an animal which has one of the many defects that Chazal enumerated (for instance, a hole in the lung), but was slaughtered properly. It is forbidden to eat, but since the Shechitah was good it is not Metamei. A Tereifah is not a Neveilah and is not Metamei, but is only Asur to eat.

2) The Asvon d'Oraisa says differently. A Tereifah is a Neveilah, but a kind of Neveilah that is not Metamei. He cites a source for this idea from the Ran in Nedarim 83b (DH Amri) who points out that there is a kind of Nazir who is allowed to touch a corpse, namely a Nazir Shimshon. The Ran writes that since we see that Nezirus does not depend on Tum'ah, the reverse may also be true -- that there can be a Nazir who is only forbidden to touch a dead body, but is allowed to drink wine.

We see that one can split up the prohibitions of Nazir. If so, one can also split up the prohbitions of Neveilah. One can have a Neveilah (a) which is forbidden to eat and is also Metamei, or (b) which is only forbidden to eat but is not Metamei. Every Tereifah is type (b). Therefore, a Tereifah is a Neveilah which is not Metamei.

3) The Gilyonei ha'Shas argues that Tosfos in Sotah 29a (DH she'Ken) agrees with this concept of the Ran. Tosfos writes that it is possible that a woman could be forbidden to her Kohen husband because she is a Safek Zonah but she is still permitted to eat Terumah. We see that it is possible to split up the prohibitions. A Zonah is, generally speaking, forbidden to her Kohen husband and also forbidden to eat Terumah. However, it might also be possible for a Zonah only to be prohibited to her husband.

4) Why are Kohanim not allowed to wear Sha'atnez after they have finished the service in the Beis ha'Mikdash but there is no Me'ilah on non-Sha'atnez clothing worn after the Avodah?

a) The Teshuvos Ben Porat 1:8, mentioned above, cites the Ritva in Yoma 69a (DH v'Teipuk) who writes that some are amazed why is it that it is obvious to everyone that the Kohanim are only allowed to wear Sha'atnez clothes at the time when they are actually doing the Avodah in the Beis ha'Mikdash, but on the other hand there is a doubt in the Halachah about whether they are allowed to wear holy, non-Sha'atnez garments inside the Beis ha'Mikdash after they have finished the Avodah?

b) The Ritva answers that the difference is that there are a few examples of Kodashim which are not subject to the prohibition of Me'ilah (for instance, Shelamim). Therefore, the Torah made the Kohen's garments like Shelamim; they are Kodesh but there is no Me'ilah.

c) The Ben Porat writes that with the Ran in Nedarim 83b we can understand the Ritva in Yoma 69a. If we would say, "Ein Kedushah l'Chatza'in" (there are no halfways in Kedushah), then the Kohanim could not wear the holy garments after they have finished the Avodah. But now Kodashim is similar to Nezirus. One can have a Nazir who possesses only half of the Dinim. A Nazir Shimshon may touch a corpse, so the Ran says that the reserve also applies: it may be that there is a Nazir who may drink wine but may not touch a corpse. The same thing may be true for Kedushah in the Beis ha'Mikdash. We learn from Shelamim that there can be Kedushah without a Me'ilah prohibition. That means that one can split Kedushah into two. Therefore, it is possible that the Kohen can wear the Bigdei Kehunah after the Avodah is finished because one can have Kedushah without Me'ilah.

Dovid Bloom