Hair dye could be used to track down criminals

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Hair dye could be used to track down criminals

“Your honor, we don’t know if the suspect is the killer, but we do know they both used Revlon Frost & Glow hair dye.” It sounds absurd, but a well-known chemistry technique could help authorities identify criminals based on their artificial hair color. Usually, hairs left behind at a crime scene are associated with DNA testing, but such a procedure requires whole, intact hairs and is often time-consuming. Because of these constraints, forensic analyses sometimes simply compare the appearance of the hair under the microscope, but these comparisons are subjective in nature and frequently inconclusive. However, new research, published online in Analytical Chemistry, might eventually provide police with a DNA-free method for objectively linking a hair to a crime. The technique uses surface-enhanced Raman spectroscopy (SERS) to precisely measure how light from a laser bounces off a hair. Vibrations within the molecules on the hair’s surface change the energy of the reflected photons and are caught by a detector. If the sample has a dye on it (or blood, drugs, ink, explosives, etc.) the laser will reflect differently, and each dye creates a unique pattern. The technique is so precise that scientists are able to identify distinct brands of dye and determine whether the dye was temporary or permanent—even when sampling a microscopic piece of hair. Furthermore, because SERS is fast and doesn’t destroy the sample, if a chemical does link a hair to a crime scene, the sample could potentially still be analyzed for DNA at a later point.

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