Chullin, Chapter 6, Mishnah 2. This chapter is devoted to the mitzvah of kisuy hadam, covering the blood of a chayah (a wild animal) or of a bird after shechitah. Our mishnah takes up a sharp question: what happens when the shechitah itself was performed properly, with a valid cut, yet for some other reason the creature may not be eaten or benefited from at all? Does the obligation to cover the blood still stand?
The mishnah opens with a list of five such cases.
"HaShochet venimtza terefah": a person performed shechitah on a wild animal or a fowl, and only afterward was it found to be a terefah. Say its lung turned out to be punctured, a defect that meant the creature could not have survived. The cut itself was flawless, yet the animal may not be eaten.
"VehaShochet la'avodah zarah": the shechitah of a wild animal or a fowl was done in the service of idolatry. In such a case not even benefit may be taken from the carcass.
"VehaShochet chullin bifnim": the creature was ordinary, non-sacred meat, and it was slaughtered within the azarah, the Temple courtyard. Unconsecrated animals do not belong there; that is not the setting for such a shechitah.
"Vekodashim bachutz": the reverse situation. This was a consecrated bird, and it was slaughtered outside the courtyard of the Beit Hamikdash rather than in its proper place.
"Chayah va'of haniskalin": here the creature, whether beast or fowl, had already been condemned to death by stoning. If, say, it had killed a human being, the verdict was that it be put to death.
"Rebbi Meir mechayev": Rabbi Meir holds that in all of these cases the obligation of kisuy hadam remains. His reasoning is that the act of shechitah was carried out correctly and legally. Once you have a valid shechitah, the mitzvah of covering the blood applies, and it makes no difference that the creature happens to be forbidden for some independent reason. The mitzvah attaches to the shechitah, whatever the status of the meat.
"VaChachamim potrin": the Chachamim disagree and exempt him. In their view, kisuy hadam belongs only where the shechitah actually accomplished something, where it rendered the creature permitted to be eaten. In every one of the cases listed here, one may not eat the animal, and in some of them one may not even derive benefit from it. So although the shechitah was technically performed as it should be, it did not function to permit anything, and therefore it does not generate the obligation to cover the blood.
The mishnah then turns to a second group of cases, where there is no argument at all.
"HaShochet venitnavla beyado": a person set out to slaughter a wild animal or a fowl, and in the course of the act it turned into a neveilah under his knife. The shechitah, in other words, was botched.
"Vehanocher": he pierced the creature's nostrils, and that is how it died, rather than through a proper shechitah.
"Veham'aker": he tore out the simanim, the pipes of the neck. Or, for example, his knife was nicked, so that the cut was not a smooth one and the shechitah was invalidated.
"Patur milchasot": in all of these he is exempt from covering the blood, and here even Rabbi Meir agrees. His whole position rested on there having been a valid act of shechitah. In these cases the shechitah was performed in an invalid manner, so there is nothing here that we would even call a shechitah, and the concept of kisuy hadam has nothing to attach itself to.