Reference for Yevamot 16:3
אֵין מְעִידִין אֶלָּא עַל פַּרְצוּף פָּנִים עִם הַחֹטֶם, אַף עַל פִּי שֶׁיֵּשׁ סִימָנִין בְּגוּפוֹ וּבְכֵלָיו. אֵין מְעִידִין אֶלָּא עַד שֶׁתֵּצֵא נַפְשׁוֹ, וַאֲפִלּוּ רָאוּהוּ מְגֻיָּד, וְצָלוּב, וְהַחַיָּה אוֹכֶלֶת בּוֹ. אֵין מְעִידִין אֶלָּא עַד שְׁלֹשָׁה יָמִים. רַבִּי יְהוּדָה בֶּן בָּבָא אוֹמֵר, לֹא כָל הָאָדָם וְלֹא כָל הַמָּקוֹם וְלֹא כָל הַשָּׁעוֹת שָׁוִין:
Testimony is given only on the full face with the nose even though there are (identifying) signs on his body and on his clothing. [If one did not see his full face, or if his nose were missing, he cannot testify (that he is dead) so that his wife can remarry, it being possible that it is not he.] Testimony is not given until his soul departs, even if they saw him meguyad ["cut" (i.e., with severed arteries) as in (Daniel 4:11): "Godu ilana" ("Cut down the tree")], and impaled, and an animal eating him [(only in a place from which the soul does not depart; but in a place from which the soul departs, they may testify that he has died.)] Testimony is given only until three days. [If they did not see him until three days after his death, they do not testify, for it is possible (after that time) that his appearance has changed, and that he is not the one they think him to be.] R. Yehudah b. Bava says: Not every man, and not every place, and not all times are the same. [Some men (such as those who are obese) swell rapidly. And there are places (such as hot places) where a body decays and changes more quickly. And there are times when it is hot, when decay and change are more rapid — all according to the man, the place, and the time. (The halachah is not in accordance with R. Yehudah.)]