Proving Paternity – Part 2

Last week, we began our discussion of the reliability of paternity testing in Halachic matters. We examined various sources, but none provided a definitive conclusion. This week’s essay will move directly to the heart of the issue.
First, it is essential to articulate a core principle: Halacha does not mandate a uniform standard of proof in all circumstances.
The Gemara in Gittin (2b) states that the rule that a single witness is considered reliable in matters of Issur (“Eid Echad Ne’eman b’Issurim”) applies only when Issur has not been established (“Lo Ischazek Issura”). In cases involving a married woman, for example, who is considered a Davar sheb’Erva, one witness is insufficient. Simply put, there are areas in which the Torah accepts the testimony of a single witness, and others where it insists on the corroboration of two.
The Gemara in Kiddushin (66b) states that establishing someone as the son of a G’rusha (divorced woman) or a Chalutza – thereby disqualifying him as a Chalal – requires two witnesses. The Tosfos Rid explains that this is because the matter is treated as a Davar sheb’Erva, which demands two witnesses.
The Shev Shmatesa (6:15) cites the Rambam (in Hilchos Sanhedrin), who rules that a single witness is sufficient to testify that a woman is divorced, thereby prohibiting her from marrying a Kohen. He raises a difficulty from the Gemara in Kiddushin that requires two witnesses to testify that a Kohen is the son of a divorcée!
He resolves the Rambam’s position: This case is, in fact, not classified as a Davar sheb’Erva, hence a single witness is sufficient to establish that the woman is a G’rusha and forbidden to marry a Kohen. However, when the issue is to disqualify her offspring from Kehuna, two witnesses are required. The reason is that any ruling that defines a person’s inherent status – a P’sul haGuf – demands the level of proof provided by two witnesses. This applies to the status of Chalalus (disqualification from Kehuna) and, likewise, to the status of Mamzerus.
On the other hand, when it comes to permitting an Aguna, we find an entirely different approach. The Shulchan Aruch (E.H. 17:24) discusses various situations in which identifying the deceased is difficult. Among them are cases where identification relies on Simanim (distinguishing marks).
The concept of Simanim is more familiar in the laws of returning lost property: When someone finds a lost item bearing identifying marks, they announce the find, and the owner can reclaim it by accurately describing those marks. This concept also applies to Agunos. When standard identification is not possible, but the body bears a distinguishing feature – for example, a uniquely shaped birthmark in a specific location – and it is known that the missing husband had such a mark, we assume that the body is indeed his. We do not suspect it might be someone else who coincidentally has the same feature.
The Shulchan Aruch defines the types of Simanim that can be relied upon for identification. The general principle that emerges from the Poskim is that ordinary signs (such as a common mole, height, or skin tone) are insufficient to establish identity and permit the wife to remarry. However, a highly distinctive mark (such as a missing finger or a significantly crooked nose) can be relied upon, and on that basis, we may permit the woman to remarry. The Poskim further classify identifying marks into varying levels of evidentiary strength: Weak, intermediate, and conclusive.
The Beis Shmuel (ibid. 72) cites the Masas Binyamin, who defines a Siman Muvhak (a conclusive identifying mark) as one that occurs, at most, in one out of a thousand cases. At first glance, this seems to provide a basis for relying on DNA testing in permitting an Aguna: DNA is a set of identifying markers embedded in a person’s cells, and the likelihood of another individual sharing an identical profile is virtually zero.
We also find that identifying marks carry weight in monetary Halacha. The Tur (C.M. 297) discusses several examples of disputes over an item in someone’s possession. In one case, Reuven claims the item belongs to him and that he gave it to Shimon for safekeeping, while Shimon denies this entirely and asserts that it has always been his. In a second case, there are witnesses that Reuven deposited the item with Shimon, but Shimon claims he already returned it. In a third scenario, there is a strong presumption that Shimon’s financial situation would not allow him to own such a valuable object, and Reuven strengthens his claim by specifying a highly distinctive identifying mark on the item. In all these cases, Reuven’s claim is rejected.
The Shach notes a nuance in the Tur’s wording. In the third case, the Tur states that Shimon “is believed to say this never happened,” rather than simply stating that “he is believed.” He explains that unlike the first two cases, if Shimon were to argue that he returned the item and that the object currently in his possession is a different one, his claim would not be accepted. Since Reuven has provided a Siman Muvhak, it is clear that the item in Shimon’s possession is the very same one that Reuven is claiming; we do not entertain the possibility that Shimon happens to own a different item bearing an identical mark. Only if Shimon maintains that the item was always his – suggesting that Reuven somehow became aware of its identifying features – would his claim stand.
From the Shach’s analysis, it emerges that a Siman Muvhak can even serve as a basis to extract property from someone currently in possession of it.
In summary: To establish or rule out ordinary Issurim, a single witness suffices; to determine Mamzerus, two witnesses are required; to permit an Aguna to remarry, one may rely on a Siman Muvhak found on the deceased to confirm his identity; and in monetary matters, a simple majority is not enough to confiscate property, but the Poskim debate whether identifying marks are sufficient.
Given this background, the key issue is how to categorize DNA testing. Should it be treated like a statistical majority, like formal testimony, or perhaps as a Siman Muvhak?
In last week’s essay, we quoted the Sefer Chasidim that suggests that some form of “blood testing” could be relied upon, even in monetary matters. However, it is difficult to draw direct conclusions from there regarding modern testing methods, which operate very differently. Moreover, the Sefer Chasidim is not clearly codified in the rulings of the later Poskim.
We must also make a further point. Scientific evidence is based on ongoing research; thus, its conclusions are always, in principle, subject to revision. Future discoveries could potentially challenge what is currently considered well established. In addition, laboratory testing always carries a margin of human error, which might suggest caution in treating such results as absolute.
On the other hand, one could argue that these concerns are extremely remote and should not be given significant weight. Even the Torah’s highest standard of proof (two witnesses) does not eliminate the possibility of error or deception. If so, why should we be more hesitant about universally accepted scientific findings?
haGaon Rav Asher Weiss Shlit”a was asked about a man who had been raised as the son of a Kohen (Shu”t Minchas Asher 3,97). At a certain point, he met a divorced woman and wished to marry her. His mother then disclosed that the man he had always believed to be his father was, in fact, unable to have children and that he had been conceived from a sperm donation. A DNA test confirmed that he was not the biological son of the presumed father. The halachic question was whether the DNA evidence could be relied upon to revoke his status as a Kohen, thereby permitting him to marry a divorcée.
In his response, Rav Asher discusses the weight of DNA testing in determining Mamzerus at length and broadens his analysis to its role in other areas of Halacha as well. At the outset, he surveys a wide range of cases throughout the Shulchan Aruch in which relying on DNA testing could have practical halachic implications.
Rav Asher rules that in areas of Halacha where we specifically require formal testimony, DNA testing does not suffice; only the testimony of two valid witnesses is effective. He explains that even though the likelihood of error in DNA testing is extremely small – even though the risk of false witnesses is higher – we nevertheless rely on witnesses not because we are certain they tell the truth, but because the Torah establishes testimony as the decisive form of proof, as the Rambam explains in Hilchos Yesodei haTorah.
He further argues that, among the various halachic forms of establishing facts – such as majority (Rov) or testimony – DNA testing is most comparable to identifying marks (Simanim). The reliance on Simanim (for example, in the return of lost objects) assumes that it is highly unlikely for another item to share the same distinctive features. DNA operates on precisely that same premise; namely, that an identical genetic profile will not be found in two different individuals. Accordingly, Rav Asher concludes that DNA evidence has the status of a Siman Muvhak, which – according to all opinions – is valid Min haTorah.
Regarding monetary Halacha, he notes the Machlokes between the Shach (mentioned earlier) and the Ketzos haChoshen over whether Simanim can be relied upon. In practice, however, they are accepted, and DNA testing may likewise be relied upon in monetary disputes. Similarly, in principle, it could be used to permit an Aguna to remarry, though in practice, additional supporting factors are generally required, and we do not rely on DNA evidence alone. By contrast, in matters such as the laws of mourning or burial – for example, when there is uncertainty about the identity of remains or their proper interment – DNA evidence can be relied upon.
However, in determining Mamzerus, witnesses are required, and DNA testing is not definitive. Rav Asher explains that although one may rely on a Siman Muvhak in monetary cases, even though a simple majority is insufficient and testimony is generally needed, Mamzerus is more severe – akin in some respects to Dinei Nefashos – and identifying signs are not sufficient.
He provides another reason to refrain from relying on DNA testing in this context: The nature of scientific knowledge is that it evolves. What is considered fact today may later be revised. While, as a rule, Halacha relies on the best available knowledge – just as Poskim have historically relied on medical expertise in areas such as the laws of Nida and Shabbos, without concern that future discoveries might overturn it – questions of Mamzerus are different. They affect not only the individual in question but also future generations. In such a far-reaching and sensitive area, there is greater reason to consider the possibility of error, however remote.
This reinforces the point we made earlier. Although witnesses could be mistaken or dishonest, once valid testimony is presented, the Torah instructs us to consider it as an accurate representation of the truth. In contrast, when relying on empirical determinations, such as DNA testing, those residual uncertainties must be taken into consideration.
Rav Asher presents one final consideration against relying on DNA testing in matters of Mamzerus. A Medrash teaches that in a case of adultery, even when the woman was actually impregnated by her husband, Hashem may alter the child’s facial features to resemble the adulterer, as a way of publicizing the sin. Based on this, Rav Asher suggests that something analogous might occur at the genetic level – even when the husband is the biological father, perhaps Hashem will alter the DNA profile somehow to reflect the adulterer instead.
Regarding the case of the man who had been presumed to be a Kohen, Rav Asher concludes that the DNA test can be relied upon to permit him to marry a divorcée. Although disqualifying someone from Kehuna ordinarily requires formal testimony, that is the case only when a person is inherently a Kohen (i.e., his father was definitely a Kohen) but later becomes disqualified (for example, due to his mother’s status). In this case, however, the issue is not disqualification but clarification: Establishing that he was never a Kohen to begin with, and that his prior status was based on a mistaken assumption. For such clarification, the lower standard of “Eid Echad Ne’eman b’Issurim” is sufficient, and DNA evidence certainly meets that threshold. Still, in practice, it is preferable, if possible, to seek additional corroboration, such as medical records, to support the conclusion that he is not the son of the presumed father.
At the end of his discussion, Rav Asher offers two further reasons not to rely on DNA testing in questions of Mamzerus:

1. Even if DNA testing were to be granted the status of testimony, in practice, its findings are presented to a Beis Din not as oral testimony, but in written form, and typically conveyed by a single individual – often someone who is not qualified to serve as a Kosher witness. This prevents it from attaining the halachic standing of formal testimony. (In theory, these issues could be addressed – for example, if judges themselves directly supervised the testing process – but, as noted above, there is a broader tendency to avoid creating or amplifying doubts in matters that could lead to Mamzerus.)
2. Every laboratory test carries some margin of error, undermining its definition as testimony. A witness testifies to what he personally saw or heard. In contrast, a technician reporting test results can only attest to the outcome. He cannot guarantee that no mistake occurred during the process, a possibility that does, in fact, exist, albeit extremely unlikely. This again highlights the earlier principle: When valid testimony is presented, the Torah instructs us to rely on it without factoring in the possibility of deception or error. However, when dealing with empirical methods of establishing facts, such as DNA testing, residual uncertainties cannot be ignored; therefore, such evidence does not attain the same definitive status as testimony.