| According
to a recent news release, the FEI Company (listed on the NASDAQ stock
exchange under the symbol FEIC) has developed a new fully automatic
gunshot residue (GSR) package. FEI Company develops, produces and
markets instruments for sub-micrometer-level imaging, analysis,
modification and fabrication. Its product portfolio includes focused
ion beam (FIB) workstations, transmission electron microscopes (TEM),
scanning electron microscopes (SEM), and systems using these
technologies in combination. The company markets these instruments
under the FEI and Philips brand names to semiconductor and data storage
device industries, universities and research institutes as well as to
organizations involved in materials research and life sciences.
While
FEI Company is headquartered in Eindhoven, The Netherlands, it also has
three other development and production centers, in Hillsboro, Ore.,
Boston, Mass., and Brno, Czeck Republic. Philips Electronics holds 55%
of the FEIC shares. It employs more than a thousand employees in these
centers and in its sales offices scattered around the world. Its active
Website can be found at http://www.feic.com
According
to the company's news release, the Gunshot Residue Package from FEI
Company eliminates the tedious and time-consuming task of manually
finding micro-particles of interest among thousands of others on a
sample. Running unattended under Windows NT® FEI's software
works completely automatically, on any Phillips' XL-series scanning
electron microscope. The software therefore also works with the XL30
ESEM which, because samples do not require conductive coating, is the
ideal SEM for forensic investigations.
Most
GSR particles have a smaller diameter (between 0.5 and 10 micron). So,
large surfaces have to be analyzed to yield results of sufficient
statistical validity. This makes manual searching simply impractical.
Instead, the GSR package runs unattended analysis on up to 16 samples
overnight, leaving the operator to validate and summarize results in
the morning. The package can hence give forensic scientists evidence
linking suspects with crimes by identifying micro-particles taken from
a suspect's skin or clothes.
Gunshot residues stick to the skin
When
a gun is fired, the gunshot residue particles - small particles
produced during the gunpowder explosions - are emitted from the back
and the muzzle. These particles fly onto the skin and clothing of the
person holding the gun. They contain elements that result from the
propellant and primer decomposing, as well as from the bullet (which
normally contains a large amount of lead), bullet coating or jacket,
cartridge components, and previous residues in the barrel.
Characteristic elements include antimony (Sb), lead (Pb), barium (Ba)
and, for special types of ammunition, titanium (Ti), and Zinc (Zn).
These cannot be completely removed by normal washing or cleaning, and
samples of the particles can be taken from suspects with adhesive tape
for further investigation.
The
tape is examiner by a scanning electron microscope (SEM) equipped with
an EDX-X-ray microanalysis system, with typically up to 16 samples
being analyzed at one time. The position and size of the candidate
particles are detected on a backscattered image, and the particles are
analyzed with an X-ray detector. The X-ray spectrum emitted from each
individual particle is compared against those in the database to verify
the particle type. Results are stored on disk in Excel spreadsheet
format. An advanced automatic calibration procedure allows complete
set-up and dynamic readjustment of the microscope column, motorized
stage, backscattered electron detector (BSD) and X-ray analysis system
without the need for operator intervention.
The
X-ray spectrum emitted by each particle can be classified into one of
35 user definable categories in accordance with the London Metropolitan
Police GSR classification scheme. Saving the settings as different
configuration files can increase the number of user definable classes.
The particles can be reviewed particle by particle, and a single-page
easy to read report is automatically generated after each sample has
been analyzed. Double clicking on the particle number automatically
centers and zooms the particle by the scanning microscope.
Philips'
ESEMs have an environmental chamber that images the specimen surface in
a gaseous environment at chamber pressures typically in the range of
0.1 to 1.3 mBar or even much higher for out gassing or wet specimens.
The ESEM can view objects like plastics, polymers, glass, wood, paints,
fibers, hairs, fingerprints, and even insects in their natural uncoated
state.
...............
Illustration below:
Graphical user interface of the GSR software, showing a typical GSR
particle spectrum in combination with the stage configuration set-up
and a control area of the Philips XL microscope.
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