Presence and collection of DNA from air and air conditioner units | Hacker News Reader

Presence and collection of DNA from air and air conditioner units

analyticalsciencejournals.onlinelibrary.wiley.com

58 pointsbookofjoe41 comments

There are attempts to do something similar outdoors to get an idea which animals are in a certain area.

https://www.science.org/content/article/dna-pulled-thin-air-...

This is clever, if used correctly. I would help prove that someone was in a building, but would not necessarily help proving that someone was in the building on a particular day.

> 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.

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.

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.

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!

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 :-)

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.

The article doesn't seem to be going that way

After a year of using an office, they still can't detect one guy but still detect the previous owner just fine

If you can only detect somebody after multiple months (up to multiple years for bad shedders) of residency, I'd imagine they would leave way easier clues than DNA in an AC unit

Is it possible to use to narrow down warrants for DNA samples? Say the police have a sample from a perpetrator and can prove that sample matches samples from a builing AC. This could be part of the evidence used to obtai warrants for the DNA of some or all current/former inhabitants of the building, especially when pairdled with unopposed expert testimony about the reliability of the methodology.

I would think (and surely hope) that would fail the probable cause test if attempted to be used for “all current/former inhabitants”.

https://nij.ojp.gov/nij-hosted-online-training-courses/dna-p...

As your link explains, in some jurisdictions all that is needed to collect biological samples is reasonable suspicion.

Geofenced warrents are already a thing. While they may not be constitutional, that hasn't stopped them from being issued and executed.

DNA from ACs could also be used to supplement other data to target specifc inhabitants with warrants.

Even if the threshold is only “reasonable suspicion”, that test fails for large numbers of people whose DNA was found in an AC.

Go read about geofenced warrants to learn how warrants for the data for large numers of people, most of whom obviously can't all be involved. Then get back to me.

Cell phone location data or automatic number plate reading is far less personal than DNA and is (IMO, rightly) treated differently.

AFAIK, location tracking requires probable cause to get a warrant. So the "different treatment" is that the standards for evidence for location data warrants are on average higher.

I'm not trying to say anything about the way things should be, but rather to correct you when you falsely reassure people that this won't and can't be used this way.

Well that's a rather horrifying thought...

Also makes it super easy to frame people: everyone is constantly shedding evidence, so just slurp some up and spit it back out somewhere you would like to "prove" them to have been.

Easy to do already with people's tobacco spit cup, or even regular drink cup residue, and such.

DNA is one of the few things that are relatively untarnished in the field of forensics which is otherwise a massive shit-show full of pseudo-science.

I am worried that this sort of work will lead to even DNA being used in a hand-wavy manner to implicate people you don't like.

https://www.bostonreview.net/articles/nathan-robinson-forens...

I believe the FBI has somewhat recently increased the number of loki needed for a match in order to claim integrity. It's possible there could have been collisions under the old standard. Most of the time it's not the forensics, but the way it's interpreted and how much weight the interpretation holds. I believe this applies to the DNA just to a lessor degree as other disciplines.

loci!

It's also true for loki.

Either this joke is going over my head or this is a term I need to look up :D

Bad joke: Loki is the Norse god of mischief, trickery, and deception (traditional). In the Marvel Universe, he occasionally tries to take over.

https://sites.stat.washington.edu/thompson/Genepi/Loki.shtml

I found this before I realized!

If it can be used for rapid detection of viral airborne diseases it can be pretty useful for Covid or bird flu etc.

They do something similar by sequencing the sewers for viral dna: https://www.nyc.gov/site/dep/whats-new/covid-19-wastewater-t...

I would be interested to know what effect talking has on the amounts of trace dna left in air.

> This study showed that human DNA can be collected from air and on surfaces that move air, such as air conditioner units, and can identify the usual users of the space as well as frequent visitors. DNA accumulated within a fairly short period of time with owners being identified after only 4 weeks of use of the tested space.

So this doesn’t seem like it would be adequate to identify criminals who visit a space one time. But I can think of various ways in which this collection might be abused - from selling information to data brokers for advertising or surveillance of regular visitors.

It also appears highly dependent on natural shedding of corneocytes. That would likely advantage a hygienic criminal who routinely exfoliates and lotions.

>Pre-operative shower using chlorhexidine gluconate (CHG)

https://uihc.org/educational-resources/pre-operative-shower-...

Shockingly those are not great instructions. The contact time is critical and it isn't really mentioned in the way it should be.

Seems like something that would exist in the universe of Gattaca

It exists in the universe of Gattaca, that's why you see him exfoliating every morning in the shower

To become less of a "good shedder"

>Offices 2–4 were all known to be occupied by the same owners for many years (see Supporting Information 1). The owners were detected as the main contributor in background samples and in most instances sufficient DNA accumulated to identify these individuals after 4 weeks of occupation. In contrast, office 1 was occupied by the current owner for only 1 year, and this owner (a known poor to intermediate shedder) was not detected at either time frame. Notably, there was a prominent male profile (further discussed in Section 10) that was detected in most background samples, but not at any other time point after cleaning. It is possible that this male profile is from the previous owner of the office who had a much longer duration of occupation and perhaps was a better shedder

The dystopian future where diseases like psoriasis get you fingered for every crime within a mile radius of your home or office

Reply on news.ycombinator.com