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Is DNA Evidence Admissible in the Halachic System?

By Rabbi David Katz

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For an audio shiur on the topic (Given by Rabbi David Katz at an alumnae Yom Iyun) please click here.


To some people, this question is obviously answered with a resounding "no". The Torah tells us in several places that we require actual witnesses to determine halachic reality. However to many others, this question is obviously answered with a resounding "yes"! After all, DNA testing is the most accurate and up to date evidence we can ever get (so far!) and of course the Torah would want us to get to the truth to the best of our abilities. And let's remember, witnesses come with a serious "margin of error", and we have sugya after sugya in the Gemara that deal with checking and double checking the veracity of said witnesses (and a very famous topic called Eidim Zommin that deals with witnesses that conspired to lie and almost got away with it!).

The real answer, in short, is that it depends. Of course this is a standard answer in halacha as many things are subject to debate based on seemingly conflicting sources or based on ambiguities in those sources. However, in this case, the debate when it comes to the "bottom line" is not about the source work. The alleged conflicts and ambiguities are in fact still there, but the poskim are able to come to consensus how to resolve those. What is, however, the determining factor when it comes to DNA testing is in what area we are in need of the evidence.

In what areas would we be interested is using DNA evidence? Here is a short list in no particular order:

  • Aveilut – identifying the dead and then to go through formal "mourning".
  • Aguna – to allow a woman to remarry if her alleged dead husband's body was not found or identifiable using "normal" means.
  • Paternity – support obligations.
  • Mamzeirut - are 2 people related and then had children together.
  • Yerusha – inheritance claims.
  • Burial for body parts to know which grave to add them to (although this in its own right raises the question of is it right to open a grave just for this and does this justify mutilating the parts themselves – nivul hamet).
  • Convictions - (like in CSI)

So what does the Torah say about requiring actual witnesses or not? Does the Torah really require humans? In theory - yes. But it isn’t 100% true and certainly not simple. First of all, not everything needs 2 witnesses. We know sometimes even one witness is considered ok. Perhaps in those cases we would also allow DNA since the Torah didn’t require a "full 2 witnesses" anyhow.

Secondly, and most glaringly, we DO allow the testimony of one witness to allow a woman to remarry. This is called takanot haagunot. So the question is what gives the rabbis the right to play with this and seemingly change a Torah law, and a serious one that could otherwise create mamzerut.

Thirdly – most of shas is full of attempts to determine reality based on all sorts of other circumstantial factors (chazaka, rov). So if it is witnesses or bust, what is the Gemara doing wasting its time?

And fourthly, and most convincing if you ask me, even witnesses have to draw conclusions. They too are only human. So a witness isn’t going into a lab and doing DNA testing, but he may testify about a death, for example, based on what he assumes to be true. He sees a body lying there and decides it is so and so based on a b c d and then goes to testify in court. So even if the system is based on witnesses, it may just be a procedural thing.

So do we allow circumstantial evidence – especially in the form of DNA which is almost 100% accurate, especially considering that testimony of witnesses in its own right are probably less accurate and the halacha recognizes that we have to live with a certain amount of doubt by definition?

Circumstantial evidence in halacha is called simanim. We are familiar with this term from hashavat aveida – the obligation to return lost objects. . The Gemara records a debate whether or not simanim are acceptable according to the Torah or are only an extra stringency applied by the Rabbis when it comes to lost property and inter-personal relationships. So in theory since this argument is never resolved we can't rely on the simanim of DNA on the chance that he Torah really wouldn’t rely on it.

However, remember those alleged conflicts in the sources? The consensus is that there are 3 types of simanim. If in fact I have really really good simanim (as opposed to bad simanim which for sure would be no good for anything – even returning lost objects - and as opposed to mediocre simanim which would be the debate in the Gemara if they are acceptable according to Torah law) then for sure the Torah would accept them as if they were witnesses themselves.

This allows us to maintain the philosophy that the Torah would for sure want us to be able to get to the truth as much as possible, yet at the same time reconcile the pesukim that seem to demand actual witnesses as opposed to anything else.

In general we say that anything with 99.9% accuracy is considered a "really good siman". Same donor DNA, with modern technology, reaches this standard. Multiple donor DNA is more subject to debate as the margin of error is a bit borderline.

So if the area in halacha is something we absolutely require 100% proof and nothing else (like mamzerut or monetary claims), then DNA evidence will still not be admissible. If however it is an area of halacha that allows for a certain margin of error, then in theory DNA evidence will work as well. There are opinions that require/allow DNA evidence if it is string together with additional forensic evidence (such as a DNA test to identify a body where you also found the person's wallet with an ID card in it).

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