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rogerbox
06-09-2011, 11:49 AM
I was reading at this (http://www.trutv.com/library/crime/serial_killers/unsolved/hair_in_hand_murders/5.html) site the following:

According to Dr. Black, he and his team were able to determine that the strands of hair represented nine months' growth and belonged to a person who lived in the United Kingdom. The person, however, had traveled abroad on two occasions, and had changed their diet twice in the three months prior to the hair being cut. According to a Dorset Police document, the person in question had traveled to "the Valencia-to-Almeria area of eastern Spain and/or the Marseille-to-Perpignan area of southern France for up to six days," approximately eleven weeks before the strands were cut. Afterward, the person visited an urban area of Tampa, Florida., for eight days, approximately two to two and a half weeks before the hair was cut.

I can easily believe that the hair strands like a ring of a tree, can show diet changes over time. But how can they single out with such astonishing accuracy where the person had been? I would be impressed with "Went from a clean rural place to a polluted urban inner city", but police in the UK can tell when someone had been to TAMPA by their hair? :dubious:

ethelbert
06-09-2011, 12:13 PM
This is just a WAG, but I seem to recall that differences in drinking water can sometimes be used to pinpoint a person's whereabouts from their hair (e;g some areas have a specific mineral signature).

rogerbox
06-09-2011, 12:21 PM
That sounds plausible, but is there some database of worldwide drinking water mineral signatures that forensic investigators have access to?

robert_columbia
06-09-2011, 02:00 PM
http://xkcd.com/683/

si_blakely
06-09-2011, 06:10 PM
This was Isotope Analysis. Geologists have pretty good databases of isotope distribution, as it can be used for a range of analysis. Forensic Scientists just tap in to that data.

Si

Chronos
06-09-2011, 09:43 PM
What isotopes would they use? Organic material like hair is mostly made up of lightweight elements like carbon, hydrogen, oxygen, and nitrogen, and most of those only have one stable isotope. Do they use the trace amounts of heavier elements, or is there something useful they can get out of the common ones?

si_blakely
06-10-2011, 05:56 AM
Strontium and Oxygen, according to wiki (http://en.wikipedia.org/wiki/Isotope_analysis#Forensics).

Si

Chronos
06-10-2011, 11:53 AM
So a little of each, then. Hm, I hadn't realized that there were other stable isotopes of oxygen.

si_blakely
06-10-2011, 02:29 PM
16O/18O ratios are used to study historical climate effects from ice cores, because there is a temperature dependent variation.

Si

Markxxx
06-10-2011, 06:00 PM
They do it like with all DNA. The figure out what probably happened, then get a hair and confront the person with what they think happened.

Police ) We got you
Guilty) You do not
Police) We have a hair with your DNA, which is always 100% correct
Guilty) OK I'm guilty

:)