If a Kohen makes a living engaging in a profession that requires him to regularly come in contact with dead bodies, then he forfeits the privileges of the Kehuna – he may not recite Birkat Kohanim, and he does not receive the first Aliya to the Torah. Examples include a Kohen who works as a medical examiner in a hospital and performs autopsies, and a Kohen who works in cemeteries. Such a Kohen is disqualified from the privileges of the Kehuna until he takes a formal, public vow that he will observe the laws of Kehuna and avoid contact with dead bodies.
This applies as well to a Kohen who is studying medicine and as part of his training dissects and works with human corpses. Regardless of whether the corpses are those of Jews or non-Jews, a Kohen may not come in contact with them even for the purpose of medical training, and if he does, then he is disqualified from reciting Birkat Kohanim and receiving the first Aliya to the Torah. If he worked with dead bodies out of ignorance, because he was unaware of the Halacha, then he is not disqualified, but if he was informed of the Halacha and knowingly violated this prohibition, then he may not recite Birkat Kohanim or receive the first Aliya to the Torah. This ruling is cited in the name of the Mahari Assad.
Summary: A Kohen who works in a profession involving contact with corpses, such as performing autopsies or working in a cemetery, or who dissects corpses as part of his medical training, is disqualified from reciting Birkat Kohanim and receiving the first Aliya to the Torah.
