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volume 8 – story 6 18 march 2010Forensic Optics:Transforming a Hairinto a Travel LogSolving crimes usually requires a lot of time and complicated investigations in order to findclear evidence. Now, it is possible to gather information about a suspect’s travel historysimply by analyzing their hair.The unchanging difficulties of solving a crime: culpritsrarely confess and dead people do not speak. Yet, somehow,the puzzle needs to be solved. Science has always been akey factor in the never-ending struggle for solving crimes.Researchers led by Rebeca Santamaria-Fernandez LGC inTeddington, London (United Kingdom), in collaborationwith the University of Oviedo (Spain), has shown that iso-tope analysis of a hair sample can tell where a person hasbeen traveling or recently changed diet, adding to the ev-er-growing scientific repertoire of a modern-day SherlockHolmes.Solving crimes often relies on associating unique fea-tures to people; a method that has been used in many waysby many civilizations throughout time. Around 4000 yearsago the ancient Babylonians were using fingerprints tovalidate contracts. By the 13th century, fingerprints wereused in many different cultures to authenticate documents.Throughout history, the uniqueness of fingerprints playedan important role for proving authenticity and uncoveringguilt. The Chinese have used them to convict criminals forover 1500 years and to this day, law enforcement and secu-rity personnel use this biometric feature to authorize accessto secured facilities and to condemn murderers.Criminal investigations always involve a multitude of as-pects and typically identify a lot of evidence before a caseis closed. Fingerprints can mistake a friend for the killeror, worse still, they can trap an innocent adversary into acomplicated murder case. The truth is that fingerprints, likemost clues, can be avoided, misinterpreted, or even faked.Circumstantial evidence, therefore, needs to be interpretedand backed up by collecting as much evidence as possible.Once this is done, the art is to identify where the evidencepoints to and, from this, to draw the right conclusions. Thetwentieth century has brought about many scientific andtechnological breakthroughs that are adding to the numberand accuracy of circumstantial evidence. The most famousof them, DNA analysis, utilizes genetic information of anindividual to prove match traces at a crime-scene with sus-pects. But sometimes, there are no DNA samples availableor nobody to match them to. Criminal investigators, there-fore, need a variety of techniques to solve their cases.“The human body is made of water, body fat, bonesand proteins,” Santamaria-Fernandez explains,” and con-tinuously produces cells, hair and fingernails.” Our bodiestake up the raw materials used for this lifelong productionthrough our breath and diet — our lifestyle leaves traces.“Keratin, for example,” she adds, “is an extremely strongprotein which is a major component in skin, hair, nails andis made up of aminoacids containing Carbon, Nitrogen,Sulphur and Oxygen. It is therefore possible to study theisotope proportions of the constituting elements and ex-tract information about food preferences or geographicalFigure 1: Strains of hair. A laser removes the outerparts and creates an aerosol of the inner, clean con-stituents of the hair. Isotope analysis of the constitutingatoms then reveals if a subject has travelled recently ornot.