DNA Testing in Halachah (Lineage)

Parshas Pekudei

וּבְצַלְאֵל בֶּן אוּרִי בֶן חוּר לְמַטֵּה יְהוּדָה” (שמות פל”ח פכ”ב)”

The good town of Hopeville was in an uproar. Mr. Lemstrum, a founding member of the Shul, had passed away. Not much was known about Mr. Lemstrum, as he had not discussed many details of his life with anyone, outside of mentioning that he had once lived an adventurous life in Mozambique when he was young. Amidst the uncertainty regarding who would inherit Mr. Lemstrum’s possessions, a person arrived who claimed to be Mr. Lemstrum’s son, and proceeded to lay claim to the estate. How can the son prove that he is Mr. Lemstrum’s heir? Would a DNA test be accepted as valid Halachic proof that he is indeed the heir to the Lemstrum estate?


There is a story told in the Sefer Chasidim (#233) regarding a rich person who traveled with his servant on a business trip to a faraway land, leaving his pregnant wife at home. Immediately after arriving in this faraway land, he fell ill and died. His servant craftily acted as if he was the rich man’s son, and “inherited” all of the deceased’s money. He quickly established himself as a philanthropist in his new community. When the real son of this rich man grew up and heard what had happened to his father’s fortune, he traveled to this faraway country in order to try to obtain his father’s money, which in fact belonged to him. The case came before Rav Sadya Gaon, who did the following test. He took a bone from the deceased (the Poskim discuss how this was permitted; we shall not deal with this aspect here), and had both the servant and the son give blood, which was deposited into two separate bowls. Lo and behold, although the father’s bone did not absorb the blood of the servant, it did absorb the blood of the true son! Rav Sadya promptly rewarded the father’s fortune to the true son. This seems to be a precedent showing that a DNA test would be halachically valid.

Opinion 1: Elyah Rabah

The Elyah Rabah (Orach Chaim 568:15) asks that this incident seems to be contradicted by the Gemara in Bava Basra (58a). The Gemara there records that there were a number of people who said that they were in fact the children of a certain rich person who had died. The person himself, however, had stated that he had only had one son in his lifetime. From the circumstances of the case, it was clear that not only was there only one true son, but that the rest of the children were Mamzerim. Which one was the son? Rebbi Banah hit upon a solution worthy of King Solomon. He proclaimed that all of the “sons” should go and hit their father’s grave until the father will come out and tell them who really is his son. All of the people did so, besides one. When Rebbi Banah observed that this person was not going, he promptly proclaimed that he is the true inheritor. How did he know that he was the heir? The other people involved were Mamzerim, who the Gemara tells us have a brazen character. This is why they would have no problem knocking on someone’s grave. Additionally, a real son would not defile his father’s grave in this fashion.

The Elyah Rabah is therefore puzzled by the story quoted in the Sefer Chasidim. If the test of the Sefer Chasidim is true, why didn’t Rebbi Banah use the test to determine the case presented to him?

Opinion 2: Rashash

The Rashash (Bava Basra 58b) explains the rationale behind the Sefer Chasidim. The Sefer Chasidim was talking about a case where one person was a son and one was an impostor. In such a case, everyone agrees one could perform such a test. However, when the party who is wrong is going to be found out to be a Mamzer, it is forbidden to do a test which will determine that someone is a Mamzer. This is why Rebbi Banah did not use the test of Rav Sadya Gaon.


Based on this Rashash, Rav Elyashiv, shlita, (Kovetz Teshuvos 1:135) answered a question posed to him regarding DNA testing. A person was told by his wife that their daughter was in fact only her daughter, not his daughter. The husband was unsure whether or not his wife was lying. Therefore he decided to do a DNA test on his daughter to see if she was really his daughter. Based on this Rashash, Rav Elyashiv Paskened that it is forbidden to do the test, as his daughter might be revealed to be a Mamzeres. (Halachically she was currently not a Mamzeres, despite the mother’s insistence to the contrary, see Teshuva at length.) The Sefer Shimru Mishpat states that this indicates that Rav Elyashiv’s opinion is that DNA testing would be valid in Halachah.

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