1) HALACHAH: FORENSIC EVIDENCE AND PASSAGE OF TIME SINCE DEATH
OPINIONS: The Tana Kama of the Mishnah (120a) maintains that testimony about the identity of a person who has been dead for more than three days is not accepted because physical changes occur in three days which render it impossible to positively identify the body. The Gemara states that if the person drowned, one may testify about his identity even after five days have passed because the water preserves the body.
What is the Halachah in practice with regard to identifying a body after three days have passed, when the body was not in water?
(a) RABEINU TAM in SEFER HA'YASHAR (#92; see previous Insight) writes that if the face is complete and not mutilated, one certainly is able to recognize a corpse even though the person has been dead for more than three days. A deceased person's face does not change after three days, and one certainly may recognize him. The Mishnah discusses a case in which the face was not recognizable and the identification of the corpse was based on marks found on the body.
(b) However, the Rishonim reject Rabeinu Tam's explanation because the Gemara says that when a person drowns, one may identify the body after three days have passed only because the water preserves it -- even if his body is found complete and not wounded. This implies that without the preservative property of water, the body would not be identifiable after three days and one would not be permitted to identify the body so that the wife of the suspected victim may remarry. According to Rabeinu Tam, however, one should be permitted to identify the body based on the face which was found complete.
Rabeinu Tam answers that the Gemara refers to a case in which the witnesses did not recognize the body with "Tevi'us Ayin" (general familiarity) since the body was partially eaten by fish (see previous Insight). They recognized the body only based on "Simanim" (specific identifying marks) on the face. In such a case, their testimony about his identity is not accepted when they saw the body three days after the death. Had they testified with "Tevi'us Ayin," however, they would have been believed even after the passage of many days. Although the Gemara does not mention in the case of drowning that the body is not whole, it is clear that this is the condition of the body (since fish often eat from the corpses they find underwater).
HALACHAH: The RAMBAM does not differentiate between whether the face is complete or not. This implies that he, too, disagrees with Rabeinu Tam. The SHULCHAN ARUCH (EH 17:25) cites Rabeinu Tam's opinion and writes that other Rishonim disagree.
2) HALACHAH: FORENSIC EVIDENCE AND DOUBTS ABOUT THE TIME OF DEATH
OPINIONS: The Tana Kama of the Mishnah (120a) maintains that testimony about the identity of a person who has been dead for more than three days is not accepted because physical changes occur in three days which render it impossible to positively identify the body. The Gemara states that if the person drowned, one may testify about his identity even after five days have passed because the water preserves the body.
What is the Halachah in a case in which a body is found and it is not known how many days have passed since the time of death? What form of testimony about the identity of the corpse is acceptable?
(a) TOSFOS writes that testimony about the identity of the corpse is accepted. Out of doubt, we assume that less than three days have passed since the time of death. The justification for such an assumption is, as the RASHBA writes, that the Halachah that testimony is not accepted after three days is only a Chumra mid'Rabanan, a stringency enacted by the Rabanan. Hence, in a case of doubt one may be lenient (particular because, as Rabeinu Tam writes, it is possible to reliably recognize a corpse after three days).
The RITVA rules that the testimony is accepted for a different reason. Since the witnesses claim that they recognize the body, there is strong reason to assume that the death occurred within three days.
(b) Others, however, question the reasoning of Tosfos and rule stringently. The conclusion of the RASHBA here (as cited by the MAGID MISHNEH, Hilchos Gerushin 13:21) and the TESHUVOS HA'RAN (#71) is that testimony about the identity of the corpse is not accepted when there is a doubt about how long ago the person died.
They rule stringently because they maintain that the limit of three days from the time of death for accepting testimony about the body is a Halachah d'Oraisa and not d'Rabanan (RIVASH #379-380). Therefore, the Halachah is stringent in the case of a doubt. Alternatively, they maintain that even if the three-day limit for testimony is only mid'Rabanan, the rule of "Safek d'Rabanan l'Kula" does not apply because the woman has a Chazakah that she is forbidden as an Eshes Ish (NODA B'YEHUDAH EH 1:29, DH v'Achshav, and SHEV SHEMAITSA 7:21).
HALACHAH: The SHULCHAN ARUCH (EH 17:27) cites both opinions.

121b----------------------------------------121b

2) HASH-M EXACTS JUSTICE FROM THE RIGHTEOUS
QUESTION: The Gemara relates that the daughter of Nechunya "Chofer Shichin" (the digger of water wells) fell into a deep water cistern. News of the tragedy was brought to Rebbi Chanina ben Dosa. After the first hour, he said, "Shalom." After the second hour, he said, "Shalom." After the third hour, he said, "She has arisen [from the pit]." When the people asked him whether he is a prophet, he replied that he is not a prophet, but that he knew that Nechunya's daughter would emerge unharmed because it is not possible that "the matter in which the Tzadik excels should cause his offspring to suffer." The Gemara adds that despite this axiom, Nechunya's son died of thirst. Even though Nechunya dedicated his life to providing water to the people who came to Yerushalayim during the festivals (Rashi), his son died of thirst because Hash-m is "exact in justice with those who are close to Him." When a person has perfected himself in an area of Avodas Hash-m, Hash-m demands from him more exacting standards.
If Hash-m does not punish a Tzadik with the same thing in which he excels in his service of Hash-m, as Rebbi Chanina ben Dosa expressed and as the first incident demonstrates, why did Hash-m allow Nechunya's son to die of thirst?
ANSWERS:
(a) TOSFOS here and in Bava Kama (50a) explains that the death of Nechunya's son by thirst is not considered a form of justice with the same matter with which Nechunya excelled. His son suffered from a lack of water, while Nechunya excelled in providing water. In contrast, if his daughter would have died by drowning in a water cistern, that decree would have been carried out with the same action in which Nechunya excelled -- the provision of water. Hash-m does not punish a person in such a way.
Alternatively, although Nechunya dug wells, he did not provide the water to fill them. The water came naturally through rainfall. Consequently, it was possible for his son to die from a lack of water, while it was not possible for his daughter to die in the pit of a well. (This is the explanation of RASHI here (DH Chofer Shichin), according to the understanding of the ETZ YOSEF. This explanation does not conform with the Yerushalmi's description that "he honored his Creator with water.")
(b) The SHITAH MEKUBETZES in Bava Kama (50a) suggests that there is no such rule that Hash-m does not exact justice from a person with the object of the Mitzvah in which he excels. Hash-m has His own considerations based on His infinite wisdom which mortals cannot comprehend.
When Rebbi Chanina ben Dosa said that it is not possible that "the matter in which the Tzadik excels should cause his offspring to suffer," he was not explaining why Nechunya's daughter suffered no harm, but rather he was describing his prayer to Hash-m on behalf of Nechunya's daughter.
(c) The MISHNAS ELIYAHU explains that the axiom that Hash-m does not permit harm to befall a person from the object of the Mitzvah in which he excels applies only to a person who performs the Mitzvah entirely l'Shem Shamayim, for the sake of Hash-m, with no other motives. No harm befell Nechunya's daughter when she fell into the water cistern because Nechunya's motivation for providing water for the visitors to Yerushalayim was purely l'Shem Shamayim. Perhaps, however, at a later time the purity of his motivation was compromised in a small way and he did not do the Mitzvah solely for the sake of Hash-m. As a result, Hash-m was "Medakdek k'Chut ha'Se'arah" with the righteous, and Nechunya's son died of thirst. (See Insights to Shekalim 14:1.)