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Comment by Footnote7341 | Hacker News Reader

While we're talking about the privacy implications of sending your DNA to be sequenced 'for fun'. 23andMe already work with law enforcement, and the data science is getting good enough that they can figure out your identity if one of your third cousins turned in a DNA sample and you never did.

The average person has around 200 3rd cousins.

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Can you elaborate on how that works?

One of my 200 third cousins did a 23andMe swab. I then committed a crime, possibly on the other side of the country*.

Law enforcement collects DNA evidence. What now?

* edit: Previously this said "or world" but that felt unreasonable for the question

The list of potential culprits reduces from perhaps tens or hundreds of thousands to about 200. Family trees are very easy discover. Check out your local Mormon genealogy center if you don't believe that. At that point they can apply standard gumshoe investigative techniques to quickly narrow it down to you.

Can law enforcement ping the 23andme database with any DNA they swab?

Yes and it appears to be some kind of weird work around where 23andme doesn't explicitly work with them. This exact technique was used to readdress some serial killer cases recently. https://www.cbc.ca/news/world/dna-from-genealogy-site-used-t... https://www.latimes.com/california/story/2020-12-08/man-in-t...

> What prosecutors did not disclose is that genetic material from the rape kit was first sent to FamilyTreeDNA, which created a DNA profile and allowed law enforcement to set up a fake account to search for matching customers. When that produced only distant leads, a civilian geneticist working with investigators uploaded the forensic profile to MyHeritage. It was the MyHeritage search that identified the close relative who helped break the case.

Basically they send in the genetic material and create an account on the site, then see which relatives it matches with and go from there.

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