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Comment by rco8786 | Hacker News Reader

> in the building on a particular day

This is a general limitation of DNA collection/analysis I would think? If you find someone's DNA somewhere, it's evidence that they were maybe there at some point in the past, but not at a specific time.

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I wonder how strong that evidence is.

For example: My DNA is probably on my coworkers clothing. Which means it is in their homes, even though I've never been there.

Interesting, I did not think of that.

Even that is a troubling assumption.

Our DNA ends up in weird places. For example, someone’s DNA is probably on this plastic bag at the bottom of the ocean…

https://education.nationalgeographic.org/resource/plastic-ba...

For sure. I used the word evidence rather than proof!

Oh that is not going to stop law enforcement (who as a general rule doesn't have to be truthful). They can say they have evidence that you were there and on the spot (if you decide to talk to them) they can get you for lying or asking when and why you were at the location in question (and the reasons). Plenty can be done with this even on a hypothetical. I think this is (in the hands of the right interrogator super helpful. It's not like someone who commits a crime is going to be up on the latest forensic tests and it does sound possible.

Maybe I've let 'GATTACA' influence my thoughts too much but it seems like all it proves is that someone was in the building that possessed a sample of a particular person's DNA.

It's not paranoia. As a sibling already pointed, we carry plenty of samples of other people's DNA around all the time.

I wonder how many snakes one would find by average in an office.

Not true. I take a used Starbucks cup and leave it in a building. Now the DNA of the person who used it is in the building. The person may never even have been in that city or country.

Gives all the baristas a good alibi :-)

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