Hair, There and Everywhere: Putting a Strand through the Ropes

That knotty, tied mess at the top of your head might reveal more than you’d imagine, should you meet your untimely end anytime soon. Only one of the over one-hundred thousand or so strands on your head needs to fall for the eagle-eyed investigator to pick up as a trace evidence sample; and then the assigned toxicologists will be able to extract, detect and decipher all the information that you’d been carrying on your noggin all along.

Just what can a toxicologist determine by running those ever-ambiguous tests on your hair? The most well-known use of such screening is to detect both therapeutic drugs and recreational drugs (think: cocaine, heroin, benzodiazepines and amphetamines) that were pulsing through your system at the time of death. It’s also useful for exactly the same purpose in life: this method can be used fairly accurately to determine the veracity of a witness statement that some illicit drug hadn’t been taken.

What isn’t so commonly understood is that tests can also reveal whether individuals have absorbed posions from their environments which are linked to certain behavioural or health problems (good news for those launching class-action lawsuits against drug companies that are emptying waste into water supplies, for instance).

Curious to learn more about what those threads have to say about your lifestlye? Read on to figure out how toxicologists handle this very worthy piece of trace evidence.


Mops of marijuana, curls of cocaine

Your hair is reservoir of intriguing forensic information: it is capable of recording medium to long-term or high dosage substance abuse and can even capture the chemical profiles of some poisonous agents in the event of a likely homicide. The process by which this occurs is fairly simple to understand — chemicals are made available after consumption in the bloodstream, which are eventually deposited into the follicle of the growing hair. As hair continues to grow out, it becomes a sort of “fossil record” that provides toxicologists with a rough timeline of what drugs were taken and when.

Still, this process isn’t as uncomplicated as it might seem: testing for chemicals isn’t standard across the population as the darker and coarser the hair, the higher the drug concentration found. It’s not fair, and this troubling fact is what raises issues of racial bias in profiling people involved in the drug trade.


Earth, wind and fire

There’s another way to analyse hair that sheds light on the environmental circumstances surrounding a death: isotopes. A quick chemistry refresher goes a bit like this: isotopes are variants of particular chemical elements (which differs from the others in its number of neutrons). Without getting too technical, it’s possible to figure out where people might have been by identifying the type of isotopes found in their hair follicles.

A great example: the University of Utah developed a method that indicates where a person last drank water, which helps law enforcement track the movements of suspected criminals or unidentified murder victims. Hydrogen and oxygen isotope levels differ in human hair across the continental US, because isotopes of these elements vary across regions. This approach isn’t limited to water, but could be applied to a range of metals that might indicate a person’s whereabouts (e.g. mineral content in soil).


Your Turn: What other types of information can you extract from a hair or a hair follicle? Is there any other technique we should have mentioned here? Let us know in the comments.



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