Slashdot Mirror
Things You Drink Can Be Used To Track You
sciencehabit writes with an intriguing story about the potential of figuring out where people have been by examining their hair: "That's because water molecules differ slightly in their isotope ratios depending on the minerals at their source. Researchers found that water samples from 33 cities across the United State could be reliably traced back to their origin based on their isotope ratios. And because the human body breaks down water's constituent atoms of hydrogen and oxygen to construct the proteins that make hair cells, those cells can preserve the record of a person's travels. Such information could help prosecutors place a suspect at the scene of a crime, or prove the innocence of the accused." Or frame someone by slipping them water from every country on the terrorist watchlist.
This has been done before: in the investigation of the poisoning of Alexander Livinenko, the traces of Polonium 210 left wherever the poisoner(s) went gave the UK authorities a very detailed trail to work with - one that not only showed the exact teapot used for the poisoning, but also provides a fingerprint of where the Po-210 was produced and at what date.
It's quite a fascinating story:
http://en.wikipedia.org/wiki/Alexander_Litvinenko_poisoning#Polonium_trails
Simply substitute Po-210 for something not deadly and you have a wonderful tracking mechanism.
'This writing business. Pencils and what-not. Over-rated if you ask me. Silly stuff. Nothing in it' - Eeyore
Dude, don't drink them! They're valuable! Do you know how hard it is to get illicit liquids like water into the US these days?
I had bottled water in my checked luggage seized last time I flew back from South America... maybe they thought I might have dissolved drugs in them or something. I figured it was better to let them keep them than ask for the water back, since all I wanted to do was catch my connecting flight (ATL airport, btw).
"Trolls they were, but filled with the evil will of their master: a fell race..." -- J.R.R. Tolkien on Olog-hai
If somehow this technique were to be come a common defense tool, then someone planning a crime could shrewdly stockpile tap water from a city with a distinct signature that isn't where the crime will take place.
I'd be impressed if you could stockpile significant amounts of water without leaving evidence in the form of empty containers, palates of water, shipping receipts, purchase receipts, and loyalty card information.
It's not that hard to destroy evidence. The hard part is destroying evidence without creating even more evidence.
Nope. Different isotopes of the same element have the same chemistry, so chemical processes won't alter isotope ratios. This is an important feature of using isotopes as tracers, since generally the tracer elements will be subject to a lot of chemical processes -- like being absorbed into the body and incorporated in to hair.
It turns out that TFA (which is just a bad summary of an actual paper) appears to have introduced the "minerals" bit. Minerals aren't involved; different water sources just have different hydrogen and oxygen isotope ratios.