Mishnayos Yevamos Perek 16 Mishnah 3

One may testify that a man died only if he can testify about seeing the countenance [partzuf ] of the face with the nose, as this allows one to identify the individual with certainty. Although there are distinguishing marks [simanim] on his body and his personal belongings, which appear to indicate his identity, one may not rely on these as identification. Furthermore, one may not testify that a person died until his soul actually departs. And even if one saw him cut open and severely wounded, or crucified, or with a wild animal eating parts of him, he may not testify that he died. Additionally, one may testify to someone’s death only when the body was witnessed up to three days following death and not after that, since the appearance may change due to decomposition. Rabbi Yehuda ben Bava says: One cannot establish general guidelines for this matter because not every person, nor every place, nor every hour is identical. Decomposition is not uniform. It occurs at different rates in different situations.

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: