“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. ||||| Criminals with a penchant for dyeing their hair could soon pay for their vanity. Scientists have found a way to analyze hair samples at crime scenes to rapidly determine whether it was colored and what brand of dye was used. Their report appears in the ACS journal Analytical Chemistry. 
 
 Richard P. Van Duyne and Dmitry Kurouski note that analyzing hairs for forensic investigations, despite what TV shows would have you believe, can be a labor-intensive and flawed process. Testing samples for DNA requires an intact bulb or root, which isn't always present. Plus, the procedure is time-consuming, which can cause a large backlog of cases. So investigators will often opt to use the more traditional method of visually comparing hair from a crime scene with samples from suspects using a microscope. But this technique doesn't necessarily provide conclusive results. Van Duyne and Kurouski wanted to find a more practical and accurate way to analyze hair. 
 
 The researchers turned to surface-enhanced Raman spectroscopy (SERS) with a portable Raman spectrometer. SERS can detect minute amounts of illicit drugs, explosives, gunshot residue and body fluids. With this method, the team could rapidly confirm whether hair samples, even microscopic ones, were dyed and what brand of colorant was used. This highly sensitive technique could help forensic investigators analyze hair quickly in the field, the researchers say. 
 
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– If you dye your hair and plan on committing a crime, be warned: A new procedure allows scientists to determine if a single microscopic hair has been dyed, if that dye was permanent or temporary, and even what brand of dye was used. Scientists used surface-enhanced Raman spectroscopy, or SERS, to gauge how light reflects off a hair. Essentially, molecules on the hair's surface begin to vibrate and "change the energy of the reflected photons," Science reports. In other words, the light reads differently depending on the dye on a sample. Not only does the technique register hair dye, scientists say it also finds small amounts of body fluids like blood, drugs, explosives, and gunshot residue, according to a study in Analytical Chemistry. Why all the fuss if scientists can perform DNA testing? For one thing, an intact bulb or root must be present in the hair sample in order for it to be analyzed for DNA, a press release notes. For another, DNA testing can be a lengthy process and the cases quickly pile up. In many cases, scientists resort to comparing a sample hair with that of a suspect under a microscope, a method that can prove both impractical and inconclusive. The SERS method is quick, easy, doesn't damage the sample, "and can be performed directly at the crime scene" using a portable Raman spectrometer, the study authors write. Another bonus: SERS' gentle approach means a key piece of hair can still be examined for DNA afterward. (Pubic hairs could help identify criminals, too.)