The usage of firearms is frequent and sometimes predominates other investigative cases. To follow the required procedures and
protocol the police officers must ask proper questions beforehand, such as:
-
what
kind of weapon was used?
-
Was the
weapon in proper working order?
-
How far
was the weapon fired?
-
Did a specific
weapon fired a bullet?
-
Did a particular
person fire the weapon?
The reconstruction of events and the
outcome of it is crucial for the investigation, it is ballistic which
thoroughly documents and investigates the firearms. It stands for the
examination of trajectory taken by the projectile and the calculation of
physics, the mathematical, meticulous knowledge which deeply hidden in numbers.
The study of firearms includes operation of firearms, cartridges, gunshot
residue analysis, bullet and cartridge case comparison and powder patter
determination. The gun is divided in to the following categories: shoulder
firearms such as rifles and shotguns and
hand guns such as pistols, automatic and semiautomatic pistols, revolvers, bear
in mind shoulder guns are less frequently used; randomly. Another distinctive
feature is diversity which is characterized by smoothbore and rifled weapons,
rifling found in gun barrels is spiral groves, cut into a barrel that impart a
twisting motion on the bullet as it leaves the barrel. The trajectory is more
stable. In single shot- and revolver-type firearms, the cartridge casing
generally remains in the weapon after firing, single shot weapons have been
made in that way to eject cases automatically. Automatic and semiautomatic
firearms, the cartridge case is ejected from the weapon automatically.
Shotguns
differ in two major ways, namely:
-
Shotgun
barrels are not rifled but are smoothbore and fire a different type of
ammunition consisting of many lead pellets, rifled slugs, or shot.
-
Shotguns
are of the single- and double-barreled break action for reloading, pump action,
semiautomatic, or bolt action types.
Small
arms cartridges or rounds are of two general types: rim fire and center
fire. Rim fire ammunition is almost exclusively .22-caliber, while larger
calibers are center fire. Some older firearms, other than .22-caliber, did use
rim fire ammunition. The terms rim and center refer to the
position of the primer located in the base of the cartridge. In a rim fired
round, the primer is in the rim in an area around the circumference of the base
while center fired rounds have the primer in the center. The primer is a small
shocksensitive explosive charge in the base of the round used to set off the
propellant powder when struck by the firing pin. The bullet is the projectile
fired from the weapon. Bullets are generally a lead alloy and jacketed with a
harder metal such as copper or brass or nonjacketed. The purpose of the jacket
is to keep the bullet intact and from breaking up when it strikes a target, to prevent
damage and to control expansion.
Gunpowder
or smokeless powder is characterized by
-
tiny
cylinders,
-
balls,
or discs of nitrocellulose or nitrocellulose and nitroglycerine in so-called
double-based powder.
When
ignited, the powder rapidly burns, giving off a large quantity of gas. The expanding
gas is the means by which the bullet is propelled through the barrel and out of
the weapon.
When
a weapon is fired, the firing pin strikes the base of the bullet detonating the
primer, the expansion of gases forces the casing against the breech, which
resists the rearward movement, and propels the bullet down the barrel. The
scratches or striations are caused by the imperfections in the lands and
grooves placed in the barrel at the time of manufacture and caused through use
of the weapon. The cartridge case is very important, the presence if it may
indicate an automatic, semiautomatic, bolt-action or slide action firearm, or a
single-shot firearm when more than one round was fired. The location of the
cases to the shooter may sometimes suggest the type of weapon fired or that a
revolver was emptied at the scene. Tests on the shooter’s hands has to be made
to determine if a weapon was recently fired. The ongoing investigation will
lead eventually to a crucial discovery and if the firearm is recovered, it is
tested to determine if it is in proper working order and if it could have been
accidentally discharged. The owner of the firearm can possibly be determined by
serial number examination. The firing the gun is never unnoticed, it seems to
be quick and it is believed it doesn’t leave much traces behind, be it as it
may, it quite misleading theory, it leaves a lot to investigate, namely, microscopic
particles of gunshot residue (GSR) are deposited on the hands of the shooter as
an aerosol. These particles adhere to the hands but are removed by washing,
wringing, or placing hands in the pockets. Handcuffing a suspect behind the
back will dislodge these particles. Studies show that GSR material will remain on
a shooter’s hands for up to 6 hours. The particles are in the highest concentration
immediately after shooting and are gradually lost over time. Because of this
time factor, GSR evidence must be collected as quickly as possible.
GSR
evidence is collected in two ways:
-
with
cotton-tipped applicators and dilute nitric acid solution for AA and ICP
analysis,
-
with aluminum stubs with double-sided cellophane
tape for SEM.
The
chemical components present on the shooter’s hands are the substances tested
for in the GSR procedure which includes:
-
barium,
-
lead,
-
antimony
A
shooting suspect’s hands should be protected until the test is given. Handcuffing
behind the back is likely to remove GSR, therefore, hands may be bagged loosely
with paper bags. Remember! Never ever put hands in plastic bags! The plastic
bags cause perspiration and hence a cleansing effect. In the case of a deceased
subject, the 6-hour time limit is flexible but the hands should be protected.
While
sketching and measuring the crime scene, it is particularly important to take a
special interest to:
-
careful
note taking;
-
detailed
measure the location of all shell casings, bullet holes, bullets and bullet
fragments, and
shotgun shot patterns that are found.
The
following procedure is to the reconstruction of the crime and can be used to
verify statements by witnesses and suspects. Do not touch the gun left at the
crime scene! Under any circumstances can You do it! First its location has to
be noted, sketches and photographs have to be taken. If the dead person is
holding the weapon, it is important to note the exact grip and position of the
weapon in the hand. The murderer may have placed it there. The way in which a
weapon is held in relation to the injuries on the body is decisive as to whether
the dead person could have produced the injuries. In the case of an automatic pistol,
the recoil of the slide may have caused a surface graze in the region of the
thumb or the web of the hand, and the presence of such an injury is suggestive
that the dead person had fired a shot with an automatic pistol. A closer
examination of the hand of the dead person may show marks of powder, especially
if a revolver had been used. From these marks, the investigator may deduce that
both hands were in the vicinity of the muzzle blast or the gap of the revolver.
One hand may have been used as a guide while the other pressed the trigger, or
both hands may have been held up in defense. In the case of long-barreled guns,
rifles, and shotguns, special attention should be given to the possibility of
the dead person’s having fired a suicide shot with the weapon.
The
position of cartridges, cartridge cases, and bullets is just as important as
that of weapons. From their position it may be possible to deduce the following
information:
-
the
position of firing,
-
direction
of the shot,
-
the
path of the bullet.
If a
bullet has penetrated a tree, piece of furniture, or wall, the shot track gives
information about the direction of the shot and often also the path of the
bullet. There is an opportunity of determining the exact course of a bullet
when it has passed through a fixed object such as a windowpane, and then struck
a wall.
The trajectory of the bullet in the skull
The
position of a bullet found at the scene of a crime should be recorded in the
same way as for weapons; bullets should be collected separately and packed so
that there can be no confusion. If two or more weapons have been used, the
bullets should not get mixed up. Great care should also be taken in collecting
and packing bullets so that the microscopic marks from the barrel of the weapon
are not injured or destroyed. For this reason, a bullet that has penetrated or
lodged in a wall should not be probed for and dug out by means of a
knife, ice pick, or chisel. Instead, a portion of the wall surrounding the
bullet should be carefully removed in one piece and the bullet recovered by
breaking away the supporting material.
Automatic pistols differ with respect to the ejection of the cases; some throw
them out to the left, some to the right, and some straight up. The case is
thrown out with a force that varies for different types of pistols. The
position of the case may give some indication of the type of weapon; however,
there is often variation from weapon to weapon. If a cartridge case has not bounced
off any object and has moreover fallen onto an underlayer that prevents it from
rolling (carpet, lawn, etc.), then its position gives a direct indication of
the type of weapon and place or direction of firing.
Bear
in mind that weapons cartridge cases, bullets, shot, and wads may carry marks
from the victim or the criminal that may aid in solving the crime. It should
always be remembered that latent fingerprints and fingerprints in blood, grease
may be found on weapons and must be protected.
A
weapon that has been used in a case of murder, suicide, or assault may contain
marks from the victim in the form of blood, hair, fragments of textiles, cloth
or fibers. Such clues may appear to be of little value, but if it is necessary
to prove that the weapon was actually used in a particular case, these clues
are then of the greatest value. Loose hairs, dried blood, fibers should be
placed into a test tube and the weapon taken and packed in such a way that
fingerprints or other clues are not destroyed. A container that suspends the
weapon with the minimum of bearing surfaces is preferred. These can be
constructed from pegboard, heavy cardboard, or similar material. Wrapping an
object in cotton, gauze, or tissue will more than likely dislodge trace
evidence. If fingerprints and bloodstains are found on a weapon, the latter
might be destroyed if the whole of the weapon is dusted with fingerprint
powder. It is convenient to make sure
that such traces of blood, hair, and the like are not on or near the
fingerprints.
In
lifting firearms, great care must be taken not to destroy evidence. The best
way to lift a pistol or revolver is to hold it with two fingers on the
checkered part of the butt, or possibly by the ring on the butt. It should be
taken as a general rule never to lift a weapon found at the scene of a crime
before first making sure that no one is in the direction in which the muzzle is
pointing; of course one should not risk being hit if the weapon fires while
being lifted. The weapon may actually be cocked so that even the slightest
movement could cause a shot to be fired.
“Under
no circumstances should an investigating officer put the weapon into his own
pocket for safekeeping. After only brief contact with pocket dust, the gun will
appear to have been unfired for some time.”
The
absence of a powder deposit or the presence of grease in the bore may also
indicate that the weapon has not been used. The examination of the powder layer
in the bore may show that the fired cartridge was loaded with black powder or
with smokeless powder. It is difficult to decide from the appearance of the
powder deposit how much time has elapsed since the last shot was fired from a
weapon. Cotton or the like must not be put in the muzzle during transport of the
weapon or when it is sent to an expert. In order to protect any deposit in the
bore, a twist of paper, rubber cap, or muzzle protector can be placed over the
muzzle. The layer of dust in the bore is always thickest near the muzzle and
decreases in thickness progressively toward the breech, assuming that it has
resulted from a long period of storage.
Many
weapons also carry proof marks. A number of European countries strictly
regulate the manufacture of firearms and require a special mark to be stamped
on the weapon’s barrel to indicate that it has been tested and found safe. In
cases of inexpensive firearms, the proof mark may be the only clue to the
manufacturer of the weapon.
From
the marks made by the extractor, ejector, and edge of the breech of an
automatic pistol on a cartridge case it is possible to determine the make of
automatic pistol from which the case was fired. Automatic pistols of different
types and makes are often constructed differently with respect to the position
of the extractor and ejector; this in turn affects the formation of the breech.
If both cartridge case and bullet are available for determination of the make, the
possibilities are increased because the number of land marks on the bullet,
their width, and the angle of twist can also be characteristic of a type of
weapon and, in any case, form a valuable contribution to the investigation.
Bullets
that penetrate hard objects are often severely mutilated therefore, every
effort must be made to preserve what little remains of the rifling impression
when a bullet is lodged in a wall, tree, or bone. In the latter case, the
method of removal will depend on whether the shooting victim is dead. If the
victim is dead, the principles for bone, tree, or wall are alike. No projectile
should be pried from its position. Instead, the supporting material and the
bullet should be cut out as one piece. Then the surrounding bone, plaster, or
wood can be broken away carefully, leaving the projectile in the best possible
condition, considering all circumstances.
The
diameter of the circle and the distribution of particles can be used to
establish the distance. Type of firearm, barrel length, and type of ammunition
are all factors that affect the size and density of the powder pattern. If the
muzzle of the weapon is in contact with the skin or within approximately 1/2
inch, the powder pattern is generally absent. This is due to the lack of space
available for expansion of the powder, so that at close range it will penetrate
the body through the entrance wound. To make a distance determination, it is
important to use the same firearm and ammunition used in the crime. A series of
test firings are made into paper or cardboard at different distances and the
test patterns are compared with the evidence. In most instances it is also
useful to make the tests on material the same as or similar to the evidence. In
certain instances the powder pattern is not easily visible. Bloodstained or dark
colored clothing causes these difficulties in visualization. Infrared
photography is helpful in bloodstained clothing cases. Chemical tests for
nitrates present in the gunpowder, such as the Walker
To sum
everything up firearms evidence occurs in many crimes, therefore,
it is particularly important to gather as much information the crime scene
provides as possible. This type of evidence is imperative, so the proper methods of handling it directs the case to
its conclusive end.
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4. Forensics Pathology.2001
5. Pathology.2005
6. Forensic DNA Technology (Lewis Publishers,New York, 1991).
7. The Examination and Typing of Bloodstains in the Crime Laboratory (U.S. Department of Justice, Washington, D.C., 1971).
8. „A Short History of the Polymerase Chain Reaction". PCR Protocols. Methods in Molecular Biology.
9. Molecular Cloning: A Laboratory Manual (3rd ed.). Cold Spring Harbor ,N.Y. : Cold Spring Harbor
10. "Antibodies as Thermolabile Switches: High Temperature Triggering for the Polymerase Chain Reaction". Bio/Technology.1994
11. Forensic Science Handbook, vol. III (Regents/Prentice Hall, Englewood Cliffs, NJ, 1993).
12. "Thermostable DNA Polymerases for a Wide Spectrum of Applications: Comparison of a Robust Hybrid TopoTaq to other enzymes". In Kieleczawa J. DNA Sequencing II: Optimizing Preparation and Cleanup. Jones and Bartlett. 2006
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14. Sourcebook in Forensic Serology, Immunology, and Biochemistry (U.S. Department of Justice, National Institute of Justice, Washington, D.C.,1983).
15. C. A. Villee et al., Biology (Saunders College Publishing, Philadelphia, 2nd ed.,1989).
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18. Human Physiology. An Integrate. 2016
Acknowledgements:
The Police Department;
https://www.politie.nl/mijnbuurt/politiebureaus/05/burgwallen.html and a Chief Inspector – Mr. Erik Akerboom ©
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