Gunshot Residue Standards
Gunshot residue
distance standards are made by firing the firearm, using ammunition like that used in the
actual case, into witness panels that consist of white pieces of
cotton twill jean cloth. Seen below are three witness panels
attached to a frame for display purposes. Normally only one panel
is mounted and fired into at a time to prevent contamination.
Several panels will be fired into at
varying distances. There are really no set distances but
an example would be to fire at distances of Contact, 6, 12, 18,
24, 30, and 36 inches.
The distance tests standards are processed
in the same way the exhibit was processed. The Griess Test
is conducted and the witness panels are chemically treated for
the presence of lead residues. The resulting residue
pattern standards are used to estimate the muzzle-to-target
distance.
The goal is to
produce gunshot residue patterns on the witness panels that represent
a minimum and a maximum firing distance. After processing the
witness panels, like those seen below, they will be compared to the
gunshot residue patterns found on the victim's clothing. A minimum
firing distance (the gun could be no closer to the garment)
will be established by finding a distance standard that displays
gunshot residues that are obviously more concentrated and in a tighter
pattern than that found on the evidence. A maximum firing
distance (the gun could not be any further from the garment)
will be established by finding the a distance standard that
displays gunshot residues that are obviously lighter and more
dispersed than that found on the victims clothing.
Below are examples of
distance standards that were fired
at distances of 3, 9, 15, 21, and 27 inches using a Ruger Security-Six
revolver and 38 SPECIAL cartridges containing plain lead, round-nosed
bullets.
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3
inch witness panel (unprocessed)
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3
inch witness panel processed for lead residues.
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3
inch Griess Test results.
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9
inch witness panel (unprocessed)
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9
inch witness panel processed for lead residues.
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9
inch Griess Test results.
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15
inch witness panel (unprocessed)
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15
inch witness panel processed for lead residues.
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15
inch Griess Test results.
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21
inch witness panel (unprocessed)
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21
inch witness panel processed for lead residues.
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21
inch Griess Test results.
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27
inch witness panel (unprocessed)
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27
inch witness panel processed for lead residues.
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27
inch Griess Test results. |
Once
standards, like those seen above, are produced they are compared to the
residues found on the victim's clothing. The results can vary and
usually do from one case to the next. Click the "Next"
button below to learn more about Gunshot Residue Distance Results.
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