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Stanford University School of Medicine

Forensic DNA reveals more than we thought, and that’s both good and bad

What's the most private piece of information someone could learn about you? The answer is probably different for everyone, but your genes have to rank high on the list - so much so that questions about genetic privacy figured heavily into recent legal battles over a Maryland law that permitted police to gather and store 13 particular snippets of DNA from anyone they arrested, not just those convicted of crimes.

The Supreme Court upheld that law on the assumption that it wouldn't violate anyone's privacy - really, how far could you get trying to determine a person's physical traits, predisposition to disease, and so on based on just 13 genetic markers?

Pretty far, actually. Michael D. "Doc" Edge, PhD, a recent Stanford graduate; Noah Rosenberg, PhD, a professor of biology, and colleagues discovered that by starting with just 13 forensic DNA markers from an individual, they could find that same person's record in a distinct, theoretically anonymous database containing hundreds of thousands of additional markers, which could be mined for private genetic information. Their findings appeared today in Proceedings of the National Academy of Sciences.

From my Stanford News story:

Previously, it had been assumed that forensic DNA collections were only useful for matching DNA samples to names already in a database - that is, for placing a suspect at a crime scene - and fundamentally could not reveal any information beyond identity matches.


Such arguments may need to be reconsidered, Rosenberg said, because when the same person is included in more than one genetic database, it may be possible to infer genetic traits from [forensic] data or to find matches across different sets of DNA markers.

That said, there is an upside, in that the technique could help scientists of all, or at least many, stripes:

The findings may also help scientists fill in missing details from DNA samples when they do not know if they are sampling the same individual. For example, when wildlife biologists want to study DNA from elusive animals, they cannot always take a blood sample. Instead, they often rely on hair or scat samples, and it can be difficult to tell if the same animal has been sampled multiple times. The same is true when sampling DNA from ancient bones recovered at archaeological sites. In both cases, Rosenberg said, the new results suggest that some of the missing genetic details could be filled in.

And then there's "a scenario that's happened to me at least twice," Rosenberg said: data sharing. It is not uncommon for collaborators from two labs to want to share different kinds of data on the same people - except it is not so simple as just sending over the data when the two datasets might have samples that are shared in common but that are labeled differently. In principle, Rosenberg said, the results of the new study could be used to match entries across datasets, making research collaborations that much easier.

Photo by Getty Images

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