Scientists have developed a new method for lifting and analysing lipstick smears from surfaces at crime scenes, which may help forensic teams identify the brand of the cosmetic and narrow down on suspects.
For years, forensic scientists have applied various methods to remove lipstick samples from crime scenes and analyse their chemical constituents. Many current methods involve difficult or expensive steps such as a tedious lipstick removal process or examination of samples by Raman spectroscopy or X-ray diffraction. However, these methods require specialised equipment and training, which are in short supply in under-funded and over-worked forensics labs. Researchers at Western Illinois University in US began with an established method of lipstick sample extraction, but then eliminated unnecessary steps and improved upon the rest.
The final method is a two-part process. First they add an organic solvent to remove most of the oils and waxes, and then they add a basic organic solvent to extract the remaining residue.
"Right now we are just lifting samples off of paper, but in the future we are hoping to use different articles and media that could be found at a crime scene," said Brian Bellott. To avoid methods that involve complex training, the team investigated three types of chromatography - thin layer chromatography (TLC), gas chromatography (GC) and high performance liquid chromatography (HPLC). GC and HPLC methods rely on injecting a sample into a machine and reading the results on a computer, whereas TLC involves looking at samples on a special surface under UV light.
Different brands of lipsticks have unique compositions of organic molecules, which give distinct chromatography signals.
(Source: PTI, Washington)
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