Related על כתובות 50:16

Rabbi Lazar said: When [does this apply]? When there is a legal complaint in court [about the guy's status], but when there is no legal complaint in court, they raise to the priesthood on the basis of 1 witness. What constitutes a legal complaint? If they said: "How did Ploni jump into the priesthood?", "He never did the priestly blessing in shul", "He never took his priestly portion"—this is not a legal complaint. [If they said:] "He is son of a divorcée", "son of a halutzah", "a natin" or "a bastard"—this is a legal complaint. Rabbi raised [someone] to the priesthood based on 1 witness. Rabbi Yose raised [someone] to the priesthood based on 1 witness.