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Law
Enforcement Technologies and Sandia National Laboratories have
developed a field-portable test kit that will provide the law
enforcement community with immediate confirmation of recent gun
use and assist in rapidly focusing on key suspects.
Subsequent to the field-testing, the swab can be retained
and analyzed by scanning electron microscopy for the presence of
lead, antimony, and barium.
The
combination of a presumptive field test that also provides
court-admissible confirmatory evidence sets a new precedence in
law enforcement technology.
The
swab / test kit is self-contained and provides results in less
than 3 minutes.
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Positive
field response of ISid-1 test swab
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Law enforcement agencies can
significantly reduce the cost of prosecution and increase their
conviction rates and by eliminating costly SEM analysis of
“blank” samples and focusing on those containing gun shot
residue.
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As part of an assessment to
evaluate the capabilities of the Field Test Kit for Gunshot Residue
Detection several hundred field tests have been performed to
estimate the probabilities of misclassification errors –
probabilities of a “positive” result using the field test kit
when no recently fired gun was involved or a “negative” result
when a gun had been fired. These
studies have shown that a both false positives and false negatives
occurred in approximately 10 percent of the tests performed.
The presumptive field test provides results that are 90%
accurate.
SEM
analysis of ISid-1 swab, 22 caliber pistol (22 short) with
backscattered image and elemental maps
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Scanning
Electron Microscope (SEM) analysis of the swab used for the field
test provides high magnification imaging of GSR particles.
The characteristic shape of the particles, along with energy
dispersive x-ray mapping yields court-admissible evidence that the
residue is the result of firing a gun.
Testing
to date has shown 100% correlation between both positive and
negative field results and subsequent SEM analysis.
A simple, 10-minute sample transfer and preparation procedure
is available.
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