Forensic analysis method for lipstick traces developed
Forensic scientists find a new way of identifying brands of lipstick at a crime scene without removing evidence from its bag.
Using a technique called Raman spectroscopy, which detects laser light, forensic investigators will be able to analyze lipstick marks left at a crime scene, such as on glasses, a tissue, or cigarette butts, without compromising the continuity of evidence as the sample will remain isolated.
Analysis of lipstick traces from crime scenes can be used to establish physical contact between two individuals, such as a victim and a suspect, or to place an individual at a crime scene. The new technique is particularly significant for forensic science as current analysis of lipstick traces relies on destructive forensic techniques or human opinion.
Professor Michael Went of the School of Physical Sciences said that Raman spectroscopy is a process involving light and vibrational energy of chemical bonds. When a material—in this case lipstick—scatters light, most of the light is scattered at its original wavelength but a very small proportion is scattered at altered wavelengths due to changes in vibrational energy of the material's molecules.
This light is collected using a microscope to give a Raman spectrum which gives a characteristic vibrational fingerprint which can be compared to spectra of lipsticks of various types and brands. Hence it is possible to determine identity of the lipstick involved.
The study, titled "Application of Raman spectroscopy for the differentiation of lipstick traces," is published in Analytical Methods.