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Are paternity, DNA and other tests admissible in Bet Din?
By Rav Yaakov Rappaport
Forensic experts, law enforcement and justice departments worldwide employ various methods to determine whether a person is telling the truth or not. Blood tests, DNA tests and polygraphs are all admissible in court. In this article, we will examine the attitude of Halacha towards such methods.
Are DNA Tests Reliable?
With regards to issues of “Pesule Edut” – unfit testimonies – the Poskim discuss DNA testing and whether it would be considered a reliable testimony in Bet Din. Most rabbinical courts in Eretz Yisrael do not accept blood tests as reliable testimony. DNA tests fall into the same category, and in most cases, they are not considered admissible proof.
The Gemara in Sota[1] states that we normally assume that the mother’s husband during the time of conception is the biological father of the baby. This is due to the Hazaka (Halachic assumption) that “Rov Be’ilot Ahar HaBa’al” – a woman will most likely be impregnated by her husband. The Shulhan Aruch[2] even applies this logic to a case where the husband is overseas for a period of time far longer than what a usual pregnancy would last.
Based on this Hazaka, many Poskim agree that DNA tests and blood tests would not be relied upon to establish that a baby’s father is someone other than the mother’s husband.
Shelomo’s Intuition
The Poskim cite another proof to this policy from the Gemara in Rosh Hashana[3]. The Gemara discusses the verse in Kohelet[4] that Shelomo HaMelech wanted to judge court cases based on his heart’s intuition. He wanted to hear the claims of both parties and draw logical conclusions without the need for witnesses. The Gemara says that a Heavenly voice declared: “Find righteousness” – to arrive at a righteous and truthful ruling you must two witnesses.
The Rambam[5] writes that the reason we need two witnesses is a Gezerat HaKatuv – lit. the Torah’s decree (an irrefutable fact). Thus, it would seem that anything less than two witnesses would be unacceptable in Bet Din – regardless of its assumed accuracy.
However, there is a general Halachic concept of “Anan Sahade” – when something is a such an undisputable reality that we are all “witnesses” to the fact, as well as an “Umdena D’Muhach” – a near absolute likelihood, as per the Gemara in Bava Metzia[6]. One could argue that blood tests and DNA tests have the same rule as “Anan Sahade” – an undisputable reality – and we can assume that the results are a known fact.
One can also argue that normally blood tests and DNA tests are used to determine the paternity of a child. The results of these tests are used to prove whether a married woman was unfaithful, and the child is a Mamzer (a Halachically illegitimate child). Since we generally don’t seek to reveal matters if Mamzerut, Bet Din would not seek out tests which may prove this.
Do Polygraphs Lie?
The accepted Halacha regarding polygraph tests is different, because these tests are not only used to reveal Mamzerim, but for many purposes. One could argue, that perhaps every Bet Din should use a polygraph test to determine who is telling the truth and who is lying.
Dayan Shapiro שליט”א, who sits in the Bet Din of the Rabbanut in Yerusahalayim, brings a strong argument against using polygraph tests:
The Gemara in Sota[7] states that one of the reasons why a suspected adulterer, a Sota, may refuse to drink the bitter waters is because of trepidation. Rashi explains that she may be scared of drinking the water, even if she is innocent, as she may be afraid that the test won’t work, and that the water will harm her even if she is innocent.
Hence, there is no proof that a woman who does not drink the bitter water is trying to hide the truth. Perhaps, she did not sin, and she is only frightened that for some reason the bitter waters will kill her anyway. Not drinking the water is not proof of guilt, since it may just be sign of fright.
The same reasoning could apply to a polygraph test. A polygraph test shows a person’s fear. When a person lies, he becomes fearful and his heart rate changes. Secular law assumes that if a person is scared and the polygraph shows that he is nervous, then he must be lying. But this Gemara implies people can become fearful even when they are telling the truth. They may just be afraid that the test won’t work.
Therefore, it would seem that a polygraph test should not be accepted in Bet Din as an indicator of guilt or innocence.[8]
It is worth noting that a polygraph test has an accuracy rate of approximately 90%, while blood tests and DNA tests have a 99% accuracy rate. This leaves room for the argument that if blood tests and DNA tests are not treated as absolute proof in Bet Din, then certainly polygraph tests should not be used.
Most Poskim conclude that a polygraph test is not acceptable in Bet Din. It is also not accepted practice for the Bet Din to threaten the use of a polygraph.
Exceptions for Agunot
When it comes to deciding Aguna cases [establishing the death of a vanished husband to permit the wife to remarry] there is a consensus among all of the Poskim that blood tests and DNA tests would be acceptable in Bet Din. After the World Trade Center collapsed, blood tests were used to permit those Agunot whose husbands’ bodies could not be identified otherwise.
This is based on Maran’s ruling in Even Haezer[9] that we can permit an Aguna based upon the identification of the husband’s clothing along on the dead body. Just as the clothing are considered proof in these matters, so should a blood test or DNA test be considered proof of the husband’s identity.
Sources:
[1] 27a
[2] Even Ha’Ezer 4:14
[3] 21b
[4] 12:10
[5] Hilchot Sanhedrin 18:6
[6] 2b
[7] 19b
[8] According to some tests conducted by Oxford University, there is a different statistic for the way a polygraph machine works on fear of lying and fear of the test itself. There are different vibrations for the two types of fear, one for fear of lying and for fear of the test.
[9] Hilchot Yibum