Attenuated
Total Reflectance-FT-IR Spectroscopy for
Gunshot Residue Analysis: Potential for Ammunition Determination
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Abstract
The ability to link a suspect to
a particular shooting incident
is a principal task for many forensic investigators. Here, we attempt
to achieve this goal by analysis of gunshot residue (GSR) through
the use of attenuated total reflectance (ATR) Fourier transform infrared
spectroscopy (FT-IR) combined with statistical analysis. The firearm
discharge process is analogous to a complex chemical process. Therefore,
the products of this process (GSR) will vary based upon numerous factors,
including the specific combination of the firearm and ammunition which
was discharged. Differentiation of FT-IR data, collected from GSR
particles originating from three different firearm–ammunition
combinations (0.38 in., 0.40 in., and 9 mm calibers), was achieved
using projection to latent structures discriminant analysis (PLS-DA).
The technique was cross (leave-one-out), both internally and externally,
validated. External validation was achieved via assignment (caliber
identification) of unknown FT-IR spectra from unknown GSR particles.
The results demonstrate great potential for ATR-FT-IR spectroscopic
analysis of GSR for forensic purposes