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| Artillery
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| The
research done by forensic scientists with regards to artillery is
very important, particularly in countries where guns are easily obtainable.
Despite what criminals think, plainly removing the gun from a crime
scene does not prevent the possibility of leaving incriminating evidence
at the scene. |
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Choose one of the topics below to read more:
--> The evidence
--> The gun
--> The bullets
--> Gunshot residue
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| As a criminal fires a
gun, the evidence is thrown in every direction. The first piece of
evidence dispersed from a gun during shooting is the most deadly of
all, the bullet. The second piece of evidence is the used cartridge
case that contained the bullet inside the gun. The third is
the burnt gunpowder expelled from the bullet and barrel of the gun
during the firing. Then lastly, the noise the gun makes as it fires
its potentially fatal bullet, for those other than the victim can
hear it. In order to understand how each of the pieces of evidence
expelled from a gun can help forensic scientists, it's important to
understand how a gun works. |
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| The
Gun |
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| Most guns work in a similar
way, that is, when the trigger is pulled, it makes the firing
pin hit the back of the sealed unit (bullet) and in turn, ignites
the small pressure- receptive charge
called a 'primer'. The primer then sets off an explosive powder in
the bullet (or in the case of a shotgun, pellets), forcing it to move
down the barrel, where it is expelled towards the target. The power
of the explosion, a powerful chemical reaction, will give the bullet
speed and force. Simple guns need to be reloaded after one or two
shots, though most guns have a bullet holding area that can usually
store up to five bullets or more. Semi-automatic weapons have an explosion
that pushes the bullet out, as well as ejecting the used bullet cases.
The weapon then automatically reloads a new bullet and pulls back
the firing pin, in preparation for the next shot. In the case of automatic
weapons, when the trigger is held back, the gun will continue firing
until the bullet holding area is empty. The most common firearms come
in the form of a revolver, a semi-automatic revolver, machine guns,
hunting rifles and shotguns (loaded with pellets). |
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| The
Bullets |
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| In the case of a shooting,
investigators must find out how many shots were fired, where the bullets
went and how each bullet got to where it is. This is done by talking
to witnesses who heard the shots or saw them being fired and also
looking for the used cartridges that may have been left on the ground.
If the shooter dropped the weapon, it is possible to tell how many
shots were fired by counting how many shots remain in the bullet holding
area. Once it has been established exactly how many bullets were fired,
the next step is to find all the bullets. An x-ray
of the victim will show bullets lodged in the body as dark shadows.
Bullets lodged in materials that are soft are especially helpful in
an investigation, as the marks left behind can be useful in the identification
of the weapon that fires it. If bullets are dented beyond analysis
upon contact with a hard surface, it is still important to find the
bullet's point of impact, as it enables investigators to trace the
path from the barrel of the gun to its final resting place. This is
done using lengths of rod and pieces of string, as well as lasers,
but lasers can only be sighted and photographed in specific light
conditions. |
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| Gunshot
residue
is found in a circular shape around the victim's bullet wound
and most importantly, on the suspect's hands and clothing. Residue
that is found on a suspect's hand can provide proof that the
suspect handled and fired a weapon recently, but the absence
of residue is not enough to prove innocence. Washing the hands
can remove all traces of gunshot residue and some weapons do
not expel any residue at all. Because of this, investigators
will often take swabs of a suspect's clothes and face to try
and find traces of residue. Other traces of residue may not
be just from the bullet, but also from the oil and metal that
can come in contact with the hands whilst loading a gun. |
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