1) THE POSITION OF THE "NISKAL" WHEN HE FALLS
QUESTION: The Mishnah teaches that in the procedure of administering Sekilah, when the witness pushes the guilty person down from the Beis ha'Sekilah, he pushes him at his loins. If he falls on his heart (on his front), then he is to be turned onto his loins (either his back or his side, as will be clarified). RASHI writes that he must be turned because when he is lying "Perakdon" (on his back) it is more disgraceful to him. Although the Rishonim in a number of places argue whether "Perakdon" refers to lying on one's front or on one's back, Rashi consistently explains that "Perakdon" means lying on one's back (see Rashi to Berachos 13b and Nidah 14a).
Rashi here seems to be saying that the person is turned onto his back because it will be a greater disgrace for him, as part of his punishment. This is difficult to understand. The Gemara throughout the Sugya emphasizes that Beis Din must make every effort to kill the person in the least disgraceful manner, because of "v'Ahavta l'Re'acha Kamocha." (SHEVUS YAKOV 1:4, cited by GILYON HA'SHAS)
Moreover, if "Perakdon" means "face down," and Rashi is explaining why he should not be left to lie face down, then why does Rashi say that he is turned over onto his back because it is disgraceful? He should explain instead that he is turned over onto his back so that he dies faster when the stone falls on his heart, as RABEINU YEHONASAN MI'LUNIL explains.
(a) The SHEVUS YAKOV cites the RAMBAM (Hilchos Sanhedrin 15:1) who explains the Mishnah differently from the straightforward understanding. The Rambam explains that the witness pushes the guilty person from behind in order that he fall on his front. The Mishnah is not saying that an effort is made to have him fall on his back, but rather that an effort is made to have him fall on his front. The Shevus Yakov suggests that Rashi also learns the Mishnah this way. When the Mishnah says afterwards that he is turned "on his loins" it means that after he falls on his face he is turned back over so that the stone should kill him more quickly. When Rashi says that lying "Perakdon" is a greater disgrace, he is not explaining why he is turned over so that his face is up, but rather he is explaining the reason for the first step: why is he pushed so that his face will be down if, anyway, he is going to be turned over so that his face is up? Why first push him down on his front and then turn him over? The witness should push him down onto his back in the first place! Rashi answers that Beis Din wants him to fall on his face because it is more disgraceful to lie on his back, and Beis Din seeks to minimize his disgrace. Afterwards, he is turned over -- either because he is dead and will no longer be disgraced by his position, or because he is alive and Beis Din wants to kill him with the stone and he will die faster with his face up.
However, this explanation is problematic. Rashi's comments are written on the words "he turns him over" ("Hofcho Al Masnav"), which implies that Rashi is explaining why he is turned over onto his back, and not why he is pushed in the first place to fall onto his front. Moreover, the Rambam's explanation is based on his Girsa of the Mishnah which does not include the words "Hofcho Al Masnav," and the Rambam does not mention anything about turning him over (see the KAPACH edition of Perush ha'Mishnayos of the Rambam). According to the Girsa of our texts, the Rambam's explanation is not consistent with the words of the Mishnah.
(b) The ARUCH LA'NER suggests a different explanation. While the RAMBAM and RABEINU YEHONASAN MI'LUNIL understand "Masnav" to refer to the back of the loins, Rashi seems to understand that it refers to the side (as it normally does). Rashi explains that if the person falls on his front, he is turned over in order that he die faster when the stone is thrown on him. Why, though, is he turned on his side? He should be turned only onto his back! Rashi therefore explains that it would be a greater disgrace for him to lie on his back, and therefore the best solution is to turn him on his side, where it will not be as disgraceful but it also will not take as long to die.