Talmud point out that it was a commission of kohanim themselves that investigated the legitimacy of fellow kohanim. Accurate lineage keeping in the Diaspora With the destruction of the Second Temple and the Jews entry to exile hard-copy lineage recording was lost. In its stead came the actions exclusive to kohanim and the absence of a disqualifying objection in Beit Din that expressed that one was a legitimate kohen. Based on a lengthy and highly-analytical responsum by the composer of the Sdei Chemed, Rabbi Chaim Hezekiah Medini concluded that the modern Kohen Muchzak is considered a valid and true kohen for all purposes that a kohen is to fulfill. Responsum of Isaac ben Sheshet (1328–1408) The source of questioning the legitimacy of kohanim is rooted in a single responsum of Isaac ben Sheshet. This fourteenth-century responsum deals with a letter to Rabbi Yitzchok detailing an event where an individual publicly humiliated a kohen. The query was as to whether it is halachic to impose an increased monetary fine to the humiliator since the subjected was a kohen, or to suffice with the standard fine afforded a non-kohen. Rabbi Yitzchok responded that "Although it is halacha that he who humiliates another by use of words is not liable, one who embarrasses a Kohen should be publicly rebuked and subject to request forgiveness from and to appease the Kohen — so long as the Kohen exhibits conduct expected from a son of Aaron". Isaac ben Sheshet continued and negated amplifying the penalty since the embarrassed kohen was not a learned Talmid Chacham kohen, but an unschooled am ha-aretz kohen. Ben Sheshet explained that even were the regular kohen to produce a lineage document certifying his direct lineage to Aaron the high priest the halachic ruling would stay, since it is found in the Talmud that the rabbis did not withhold from humiliating a "lineage-verified kohen" who was not well-versed in Torah (Am Haaretz) all the more so today's kohen who cannot produce his lineage document does not receive an amplified penalty". Of note is that the Shulchan Aruch (Tur Choshen Mishpat 420:24) rules that the humiliator of a kohen is liable to pay amplified compensation. Isaac ben Sheshet's words "today's Kohen who cannot produce his lineage document", which he intended on using as a sidebar explanation to his final ruling of standard compensation, over time evolved into an underpinning foundation for Poskim