Related על כתובות 2:8

And similarly with two men—this one says, "My fellow is a kohen" and the other one says, "My fellow is a kohen"—they give to them [the priestly gifts]; but for priestly pedigree [i.e. to pass onto their children] they are not believed until there are 3 men, in order that 2 of them testify about the 3rd and the other 2 testify about the other 3rd. Rabbi Yehudah says: They don't even give them [the priestly gifts] until there are 2 to testify about this one and 2 to testify about this one. They raise someone to the priesthood, to being a Levite or an Israelite on the basis of one witness; but they do not lower someone except on the basis of 2 witnesses. Rabbi Yehudah says: Just as they don't lower someone except on the basis of 2, they don't raise except on the basis of 2.

If rumour was spreading in town—Rabbi Yose says: Rumour is not evidence, rather anyone who has a valid legal complaint should come [to court] and say it. Rabban Shimon ben Gamliel says in the name of Rabbi Shimon ben Ha-Sgan: They raise [someone] to the priesthood based on 1 witness, and not even just 1 witness but even on the basis of a woman['s testimony]. And the woman doesn't even have to come to court, just when she said "They gave to him" [his priestly gifts, this off-hand comment is enough to raise someone to the priesthood].