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.

Comments

Forensics

[girlintraining]

I can see this science being abused. Whether your body contains a certain chemical signature or not is still circumstantial evidence, but increasingly our justice system (like many countries) are using it to give carte blanche access to a person's private information and life. Worse, if the request is later determined to have been falsified or exaggerated, the evidence gathered as a result of that request is still considered valid for the persecution of not just the original crime, but anything else uncovered as a result.

Thanks to shows like CSI and confidence in science, we want DNA samples, hair, urine, and a billion other things -- and believe that their presence somehow proves or disproves guilt. This is despite the fact that such evidence can be manufactured with ease -- the prime example being Photoshop for photographs, but virtually every technology you have around you can be used against you in some fashion or manipulated to imply or explicitly state something that is not true. Yet the courts rarely ask that samples be tested for contamination, or refuse to re-hear cases where the lab clearly and undeniably compromised the results.

It used to be that testimony was the primary vehicle in obtaining a conviction. Now we're increasingly using evidence that neither the judge, jury, defense, or even prosecution fully understands to take away other people's freedoms, sometimes under false pretext. While this particular technology is neither good nor bad, the system that will incorporate its use may be fundamentally flawed.

Re:Not enough degrees of freedom

[Red Flayer]

So you won't be able to tell the difference between, say, a person who lived all year in Illinois (with a moderate isotope ratio) and a person who flies back and forth between Montana and Florida (who'd have a mix of "heavy" and "light" water in their system.)

Not true. The fact that the oxygen isotopes are bound into hair means that we have some kind of a time reference.