For the source text click/tap here: Yevamot 120
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When witnesses come to testify that a person has died, it is obvious that they must be certain that they saw that person dead.
Thus, the Mishna on our daf rules that even if the witnesses saw someone being crucified or being mauled by a wild animal, they cannot testify unless they are sure that he was killed.
The Mishnah states that the testimony of a witness about the identity of a corpse is not acceptable unless he recognizes the forehead and nose of the dead person.
We learn that a witness must look upon the countenance (defined as the cheeks) of the face rather than other identifying marks or characteristics.
Even if an animal has begun to rip a person apart, the body must be identified within three days of dying.
Otherwise the face will have begun to change in early stages of decomposition.
This leads us to an exploration of the victim identification then and recently how ZAKA made such decisions as well as the Yad Vashem 2017 symposium on How to Deal with Holocaust Era Human Remains