Hyperspectral imaging combined with multivariate statistics is an approach to microanalysis that makes maximum use of the large amount of data in forensics analysis. VNIR, SWIR, Raman and thermal emission spectroscopy have been used to aid in forensic sciences. Several papers in the literature demonstrate the power of combining spectroscopic specificity with the rich information of hyperspectral imaging.
One study examined the efficacy of hyperspectral imaging-enabled microscopes to identify chemical signatures in simulated bioagent materials. Hyperspectral imaging successfully identified particles with trace elements that would have been missed with a more traditional approach to forensic microanalysis. (Brewer, 2008)
Victim detection from hyperspectral images was performed using chemometric processing of the infrared hyperspectral data. Infrared hyperspectral images provided a complete picture of the surrounding environment, facilitating victim detection. (DeCubber, 2009)
Raman chemical imaging (RCI) has been used to detect and identify explosives in contaminated fingerprints. Bright-field imaging was used to identify regions of interest within a fingerprint, which was then examined to determine chemical composition using RCI and fluorescence imaging. Explosives in contaminated fingerprints were identified this way and their spatial distributions obtained. Identification of explosives was obtained using Pearson’s cosine cross-correlation technique using the characteristic region (500 – 1850 cm-1) of the spectrum. This study shows the ability to identify explosives non-destructively so that the fingerprint remains intact for further biometric analysis. (Emmons, 2009)
Hyperspectral imaging in the VNIR region can be used forensic document analysis to identify document forgeries. Falsified documents can usually be identified from the spectra of critical parts of documents to discern real differences in inks that otherwise appear identical to the human eye. Slight, but well-defined spectral differences can be resolved using principal component analysis (PCA) as shown here.
Hyperspectral imaging color inspection technology has been used to enhance visualization of bloodstains on dark surfaces in crime scene investigations. While DNA and similar analysis processes can assist in determining the biological source of the stains, they cannot determine the pattern of the bloodstain if it is not visually obvious. Researchers at the National Criminal Justice Reference Service found that knowing how the bloodstains were formed, as interpreted by their patterns, was often more important than evidence from DNA testing. After extensive study, these researchers found that hyperspectral imaging was a good solution for recognizing the presence of blood and analyzing the stain patterns, without destroying crucial information. (DeForest, 2009)
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