One may only testify [that a man is dead] if he saw the face and nose, even though there are [identifying] marks on the body or clothing. One may only testify [that a man is dead] if he [actually] saw him dead, but not if he saw him cut, hanging, or being devoured by a wild beast. One may only testify [if he saw the body] within three days. R' Yehudah ben Bava says: Not all men, or areas, or times are alike.