New Forensic Technique for Analyzing Lipstick Traces
A
study by forensic scientists at the Univ. of Kent has established a new
way of identifying which brand of lipstick someone was wearing at a
crime scene without removing the evidence from its bag, thereby avoiding
possible contamination.
Using a technique called Raman spectroscopy, which detects laser
light, forensic investigators will be able to analyse 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.
"Continuity of evidence is of paramount importance in forensic
science and can be maintained if there is no need to remove it from the
bag. Raman spectroscopy is ideal as it can be performed through
transparent layers, such as evidence bags. For forensic purposes Raman
spectroscopy also has the advantages that microscopic samples can be
analyzed quickly and non-destructively," says Prof. Michael Went of the
University’s School of Physical Sciences.
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.
Research into applying the same method on other types of cosmetic
evidence, such as foundation powders, eye-liners and skin creams is also
underway.
Source: Univ. of Kent
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