Yevamot 122 - Hearsay about death
If one heard women saying that so-and-so died, he can later testify about it in court, so that the wife of so-and-so can re-marry. Even the talk of minors, who are not considered legally competent, suffices for this.
But perhaps those minor children were just playing funerals and eulogies, as they are wont to do? - We mean a case when they are coming back from a funeral and mention people who were present there.
An idolater's statement is also sufficient to testify - provided that he was just relating the events, without any self-interest.
Rabbi Akiva told a story: once he had to go to Nahardea in Babylon, in order to establish a leap year. While there, he encountered Nechemyah from Beit Deli. Nechemyah told him that, contrary to the prevailing opinion at that time, he had a tradition from Rabban Gamliel the Elder that one witness of the husband's death was enough to allow the wife to re-marry. Since the country was full of ravaging troops, he appointed Rabbi Akiva as his messenger to relate this back in Israel. When Rabban Gamliel the grandson heard it, he rejoiced, because they now found a corroboration for this opinion, already espoused by Rabbi Yehudah ben Bava, and the law was established - thus allowing many widows to re-marry.
Art: Children Playing with Hoops in a Street by Milly Childers