2,240. A Self-Proclaimed Kohein

Hilchos Issurei Biah 20:12

If a person testifies in court that he saw a certain individual and his brothers divide trumah that was left to them by their father, who was a kohein, we do not consider him a kohein based on this testimony. This is because he might be a chalal who took his share of the trumah inheritance in order to sell it.

Hilchos Issurei Biah 20:13

Nowadays, if a person comes and claims to be a kohein, his word is not accepted and we don’t consider him a kohein based on his assertions. He doesn’t get the first aliyah, recite Birkas Kohanim or eat sanctified food that is eaten within Israel until a witness corroborates his claims. He does, however, prohibit himself from marrying a divorcee, a zonah or a chalalah, and from rendering himself unclean through corpse impurity. If he marries one of these women or renders himself unclean, he is lashed. If a woman (who is prohibited to kohanim) is intimate with him, she’s rendered a doubtful chalalah.