The Acceptance of DNA Evidence in Halachic Law

Dear Rabbi In my professional role within police forensic investigation, I frequently utilize DNA analysis to solve cases, where it serves as a pivotal form of forensic evidence. As a practicing Jew, I am keen to understand the perspective of halacha on this matter. Could you please provide insights into how DNA evidence is regarded within Jewish law? Any guidance or references to texts that discuss this topic would be greatly appreciated.

Thank you for your question.
As you wrote DNA is considered a form of evidence in the civil courts, however when it comes to Halacha there has been a great debate as to it use for evidence for example to assume a married man as dead in order to permit his wife to remarry. It is a very interesting subject which I would be happy to share with you.
Halachic law traditionally relies on the testimony of two witnesses to establish the facts in a case, as stated in Deuteronomy 19:15 "על פי שני עדים יקום דבר" ("By the testimony of two witnesses shall a matter be established"). This teaches us that generally, one can only rely on direct human testimony in judicial proceedings.
However, halachic law also recognizes other methods of identification in certain contexts. For example, the Torah discusses the identification of lost items, instructing that thorough investigation and specific identifying marks (simanim) can establish ownership, as indicated in Deuteronomy 22:2 "עד דרוש אחיך אותו" (“until your brother seeks it; then you shall restore it to him”). The Talmud in Tractate Bava Metzia (page 27b) writes this as a source that a claimant must provide identifying marks to prove ownership of a found item.
Similarly, the concept of majority (rov) is used in halachic decision-making. For instance, if a piece of meat is found in an area with nine kosher shops and one non-kosher shop, one can assume it came from a kosher source based on the principle of majority, as derived from the verse "אחר רבים להטות" ("Follow the majority").
The question arises whether these principles can be applied to identifying a body when witnesses are not available. In Tractate Bava Metzia 27b, there is a discussion on whether simanim (identifying marks) are recognized by the Torah (min hatorah) or are rabbinically mandated (derabbanan). The Talmud clarifies that only a strong and distinctive mark (siman muvhak) is considered valid by Torah law, while less distinctive marks are rabbinically accepted.
This is brought in the Shulchan Aruch, with guidelines pertaining to the identification of a deceased husband, for determining if a widow may remarry. The conditions under which identification can be considered reliable are specifically detailed:
Shulchan Aruch, Even HaEzer, Laws of Marriage, Siman 17, 24:
"If a man is found dead or has been murdered, and his forehead, nose, and facial features are intact, allowing for his recognition as a specific individual, such features enable witnesses to testify to his identity.
However, if these features are missing, and even if his belongings bear very distinct marks, these cannot serve as reliable evidence due to the potential for mistakes. Similarly, mere signs on his body, such as scars, are insufficient for testimony on their own.
Nevertheless, if there are exceptionally clear and distinct physical signs on his body, such as an unusual physical attribute like an extra or missing limb, or a significant alteration to one of his body parts, witnesses may testify based on these. Rema adds, that general characteristics such as height, complexion (pale or flush), are not considered definitive enough for recognition.”
Based on the above In the sefer Ein Yitzchok, we find a teshuva (responsa) by Rav Yitzchak Elchanan Spektor, where he accepts a photograph of a deceased individual as valid evidence of the person's death.
This leads to an intriguing question: How does DNA evidence compare to traditional methods of identification as discussed in in the halachic texts above?
There is significant debate among poskim (halachic authorities) regarding whether DNA can be classified as a siman (identifying mark). Since unlike visible distinguishing features, DNA identification relies on the process of elimination and the statistical probability that no one else shares the exact same genetic profile. Given this basis, some argue that DNA should not be considered a siman muvhak (conclusive sign) but rather is akin to employing the principle of rov (majority), which alone does not provide sufficient grounds to permit a woman to remarry.
Even if we were to consider DNA as a potential siman (sign), we must evaluate whether it qualifies as a siman muvhak (conclusive sign) based on its reliability and distinctiveness. First we have to know that DNA evidence is particularly reliable when comparing a deceased person's DNA with samples from their personal belongings, like saliva on a toothbrush. (However, its accuracy decreases when the comparison is limited to DNA from family members).
Even though DNA can get 99.9 accurate, there is still room for mistakes. For example contamination is a big problem; if other biological materials mix with the DNA sample during collection, storage, or analysis, it can lead to wrong results. Human mistakes, such as errors in handling, labeling, or analyzing the samples can skew outcomes.etc.
Given these factors, many rabbinic authorities consider DNA evidence as a “better than average” siman (siman beinoney chazak), rather than a definitive one (siman muvhak). DNA can be part of the evidence used to construct a case but may not stand alone in identifying a deceased person without additional corroborative evidence.
Rav Yosef Shalom Elyashiv addressed this issue following the September 11, 2001 attacks. Some Jewish workers were missing and presumed dead, leaving their wives potentially as agunot (chained wives unable to remarry). Rav Elyashiv used DNA evidence, combined with other forms of evidence, to build a halachic case that these husbands had indeed perished, thus permitting their wives to remarry.
In summary, while DNA evidence is highly valuable and reliable in forensic science, its acceptance in halachic law requires careful consideration of its limitations and the context in which it is used. It is generally viewed as a strong supportive tool rather than definitive proof. This nuanced approach allows for the use of DNA evidence within the framework of halachic principles, particularly when combined with other forms of evidence.

1. Deuteronomy 19:15 and 22:2
2. Talmud, Tractate Bava Metzia
3. Shulchan Aruch, Even HaEzer, Laws of Marriage, Siman 17, 24
4. Sefer Ein Yitzchok