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Ballistics
Handguns
• Definition: A firearm designed to be fired from
the
hand
and
having
a
rifled
barrel
and
a
revolving cylinder containing several chambers each of which holds one cartridge.
• Auto‐loading pistols: A handgun designed to
be fired from the hand and having a rifled
barrel and a removable magazine storing
cartridges with a mechanism for auto‐loading.
Rifles
• Definition: A firearm with a rifled barrel
designed to be fired from the shoulder.
• Types:
– ng e s o
– Lever action
– Bolt action
– Pump action
– Auto‐loading (erroneously called "automatic
rifles")
Shotguns
• Definition: A firearm with a smooth bored barrel designed to fire multiple pellets and to be fired from
the shoulder.
• Types
– ng e s ot
– Over and under
– Double barrel
– Bolt action
– Lever action
– Pump action
– Auto‐loading
Submachine/Machine Guns:
• A firearm, with a rifled barrel firing pistol
ammunition, designed to be fired from the
shoulder or the hip and capable of fully
.
• A firearm with a rifled barrel firing rifle
ammunition and capable of fully automatic
fire.
• Submachine guns are more portable.
Small Arms Ammunition
• Cartridge Case
• Primer
• Propellant• Bullet
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Cartridge Case
Function:
Expands and seals chamber against rearward
escape of gases.
Compos t on:
Usually brass (70% copper 30% zinc); Also
plastic and paper in shotgun shell tubes.
Cartridge Case
Shape: (a) straight ("always" pistol ammunition)
(b) bottleneck ("always" rifle ammunition)
x rac or ange:
configuration at base; rimmed, semi‐rimmed,
rimless, belted, rebated.
Headstamp:
manufacturers identification imprinted or
embossed on cartridge case.
Bullet
Function: the part of the cartridge which exits
the muzzle.
• Composition: a ea a oye w t t n an or ant mony
with/without copper or copper alloy "gilding"
(less than 0.0002 inches thick).
(b) metal jacketed with lead or steel core and
jacket of copper‐zinc, copper‐nickel or
aluminum (0.0165 to 0.03 inches thick).
Bullet
Shapes:
(a) lead bullets ‐ roundnose, wadcutter, semi‐wadcutter, hollowpoint; generally all have
cannelures or
rooves.
(b) metal‐ jacketed
(i) full jacketing in military ammunition
(ii) partial jacketing in hunting rifle and semi‐automatic pistol ammunition: semi‐ jacketed
soft point, semi‐ jacketed hollow point, Silver‐tip (aluminium).
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Bullet
Uses:
(a) Lead bullets
‐ traditionally
only
for
revolvers
and .22 caliber rimfire ammunition; copper
. ‐
ammunition.
(b) Metal‐ jacketed bullets ‐ traditionally for
semi‐automatic pistols and high velocity
rifles.
Primer
Function:
Explodes on
compression
igniting
the
propellant.
Composition: • Common y ea styp nate, arium nitrate, antimony
sulphide.
• Typically all 3 elements (lead, barium antimony) in
centerfire ammunition but sometimes lead only or
lead and barium in rimfire ammunition.
• Elemental trace tests used to determine if person
fired a weapon.
Primer
Location:
(a) centerfire. Centrally placed primer assembly
comprising primer cup (struck by firing pin),
, .
(b) rimfire. No primer assembly. Primer spun
into rim of cartridge case (rim struck by firing
pin) and in contact with propellant.
Propellant
Function: • Burns to produce large volumes of gases under
pressure.
Composition:
• , , now obsolete. Smokeless powder (nitrocellulose
with/without nitroglycerine).
Shape:
• Sheets of smokeless powder cut into disc, flake or cylinder shapes. Alternatively produced as ball and
flattened ball smokeless powder (Winchester) which
may be
coated
with
silver
‐black
graphite.
Cartridge Cases
• Cartridge cases or shotshell casings
examinations can determine the caliber or
gauge, the manufacturer, and whether there
.
• The microscopic characteristics of evidence
cartridge cases and shotshell casings can be
examined to determine whether they were
fired in a specific firearm.
Cartridge Cases
• Examinations of unfired cartridges or shotshells can determine the caliber or gauge
and whether there are marks of value for
comparison. • Examinations can also determine whether the
ammunition was loaded into and extracted
from a specific firearm.
• Unfired and fired cartridges or shotshells can
be associated through manufacturing marks.
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Comparison of Casing Striations
Image from http://www.crimescenetwo.com/index2.html
Cartridge Case from Anglo‐Zulu Battle
(Archeology) Ballistics
• Studies have shown that no two firearms,
even those of the same make and model, will
produce the same unique marks on fired
.
• Manufacturing processes, use, and abuse
leave surface characteristics within the firearm
that cannot be exactly reproduced in other
firearms.
Ballistics
• Firearms do not normally change much over time.
• This allows for firearms recovered months or even
years after a shooting to be identified as having fired
a specific
bullet
or
cartridge
case.
• Tests have been conducted that found that even
after firing several hundred rounds through a firearm
the last bullet fired could still be identified to the
first.
Ballistics Comparisons
• If dissimilarities in class characteristics are
found or if a general lack of good class
characteristics are present no further
.
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Ballistics
• Rifles and handguns (but not shotguns) have
rifled barrels.
• The rifling comprises spiral grooves cut the
.
• The raised metal between the grooves is the
lands. Typically, caliber is measured from
country to country but usage is inconsistent.
Ballistics
• When a rifled weapon is discharged, the rifling
produces
marks
on
the
bullet
as
it
passes
down the barrel.
• Some markin s have "class characteristics" indicative of the make and model of the
firearm.
• Other markings have "individual characteristics" which reflect imperfections peculiar to a particular firearm and may allow
its specific identification.
Bullets
• Fired bullets can be examined to determine
the general rifling characteristics such as
caliber and physical features of the rifling
impressions and the manufacturer of the
bullets.
• The microscopic characteristics on evidence
bullets can be compared to test‐fired bullets
from a suspect firearm to determine whether the evidence bullet was fired from that
firearm.
Bullet Class Characteristics:
• Number of lands and grooves (usually 4 to 6 but
range from 2 to 22).
• Diameter of lands and grooves.
• Width of lands and rooves.
• Depth of grooves.
• Degree of twist (twist is the number of inches/cms of
bore required for one complete rifling spiral).
• Direction of rifling twist (commonly right/clockwise,
less commonly left/counter‐ clockwise e.g. Colt).
Comparison
Microscope
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Bullet viewed with Comparison
Microscope
Distorted Bullet
Comparison of distorted bullet
Bullet Individual Characteristics:
• Imperfections of grooves (most pronounced in
lead bullets).
• Imperfections of lands (most pronounced in
.
Firing Pin Impressions Cartridge Case and Primer
Characteristics
(1) Type of breech block marking.
(2) Size, shape and location of extractor marks.
(3) Size, shape and location of ejector marks.
,
most important identifying marks in rimfire cartridge
cases).
• Fingerprints are rarely recovered from firearms but
may be obtained from cartridge cases.
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Cartridge Cases Don’t Match Cartridge Cases Match
Other Firearms Evidence
• Obliterated and/or altered firearm serial
numbers can sometimes be restored.
• Firearms can be test fired to obtain known
ammunition components such as bullets,
cartridge cases, and shotshell casings.
Other Firearms Evidence
• Firearms examinations can determine the
general condition of a firearm and whether the firearm is mechanically functional.
• Tri er‐ ull examinations can determine the
amount of pressure necessary to release the
hammer or firing pin of a firearm.
• Examinations can determine whether a
firearm was altered to fire in the full‐automatic mode.
Other Firearms Evidence
• Shot Pellets, Buckshot, or Slugs
– Examinations of shot pellets, buckshot, or slugs
can determine the size of the shot, the gauge of
the slug,
and
the
manufacturer.
• Wadding
– Examinations of wadding components can
determine the gauge and the manufacturer.
Firearms Evidence
• Shot pattern examinations can determine the
approximate distance at which a shotgun was fired
by testing a specific firearm and ammunition
combination at known distances.
•
noise of a firearm by suppressing sound during firing. Testing can determine whether a muzzle attachment can be classified as a silencer based upon a
measurable sound‐reduction capability.
• Gun Parts examinations can determine the caliber and model of gun from which the parts originated.
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DRUGFIRE
• DRUGFIRE is an automated computer
technology that
links
firearms
evidence
from
serial shooting investigations used in firearms
.
• DRUGFIRE is designed to help labs maintain
and search Open Case Fired Ammunition Files. •The images of questioned cartridge cases and
shotshell casings can be scanned into
DRUGFIRE to compare with evidence from
other shooting incidents.
DRUGFIRE
• DRUGFIRE integrates forensic database information,
video, audio, digital images, and telecommunications
technologies to simulate the functionality of forensic
equipment.
• Through the use of state‐of ‐the‐art technologies,
DRUGFIRE enhances the capabilities of the forensic
firearm examiner.
• As of October 1, 1999 there were over 225,000
images in the system which have led to over 3700
Cold
Hits.
IBIS
• Forensic Technology Inc. (FTI) is a company dedicated
to enable forensic sciences to achieve increased
effectiveness through the application of automation
technology.
• A former firearms examiner with the Royal Canadian
Mounted Police recognized that computer
technology could be useful in firearms identification
and approached Walsh Automation Inc. with a
development proposal.
• Walsh Automation decided to develop an image
analysis system designed expressly for the forensic
firearms examiner.
IBIS
• FTI achieved its initial breakthrough with the
development of BULLETPROOF, an image analysis system for analyzing and identifying spent bullets.
• FTI also developed BRASSCATCHER, an FTI cartridge
case solution.
• BULLETPROOF and BRASSCATCHER were successfully
integrated to form IBIS (Integrated Ballistics Identification System), a single system able to
capture, store, retrieve, and perform searches on
both damaged or pristine bullet and cartridge case
images in one system.
Gunshot Residue
• The deposition of gunshot residue on
evidence such as clothing varies with the
distance from the muzzle of the firearm to the
target. • Patterns of gunshot residue can be duplicated
using a questioned firearm and ammunition
combination fired into test materials at known
distances.
• These patterns serve as a basis for estimating
muzzle‐to‐garment distances.
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Gunshot Residue from Different
Firing Distances
Image from http://www.crimescenetwo.com/index2.html
Detection of Gun Shot Residues
• It is possible to detect traces of the metals barium, antimony and lead, on the back of the firing hand of individuals
who
have
fired
a gun.
The
metals
originate from the primer.
hydrochloric acid or 5% nitric acid) are used to
recover residues for analysis by flameless atomic
absorption spectrometry (FAAS) and neutron
activation analysis (NAA).
• Adhesive material is used to recover residues for analysis using scanning electron microscopy and
EDAX.
The gunshot residue deposited in a gunshot wound can be detected by
using scanning electron microscopy coupled with energy‐dispersive x‐
ray microanalysis to demonstrate the characteristic elemental pattern
of the primer residue with lead, antimony, and barium.
Detection of Gun Shot Residues
• All three metals are not always present in rimfire
primers.
• Neutron activation only detects antimony and
barium, and must be used in conjunction with FAAS to
detect lead.
• an are o quan a ve e emen a
analytical methods which do not distinguish the source
of the metals. False positives are therefore
theoretically possible.
• Although SEM with EDAX can potentially absolutely
identify all gunshot residue. In practice, residues are
detected in 90% of persons who have fired
handguns, but
only
50%
of
persons
who
have
fired
rifles and shotguns.
Detection of Gun Shot Residues
• The quantity and distribution of the three metals can
be described as consistent or not consistent with
gunshot residue and with firing a weapon.
• Residues on the palms of the hands could indicate a
,
weapon.
• In suicides, residues are often detected on the non‐
firing hand used to steady the muzzle against the
body.
• Residues of barium alone may be the result of contamination with barium rich soil.
SEM and Gunshot Residue
Image From http://www.crimescenetwo.com/index2.html
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Detection of Gun Shot Residues
• Plastic gloves should be worn by the evidence
technician when
taking
the
hand
‐wiping.
• The cotton swab is moistened with two or
.
• About 20 seconds of swabbing is
recommended and important per swab. Each
area is swabbed twice.
Detection of Gun Shot Residues
• The four areas swabbed are the backs of both hands
and
the
palms
of
both
hands.
• On the back of the hand the radial aspect of the
forefinger, the dorsal aspect of the thumb, and the
skin web between is swabbed.
• On the palm of the hand the palmar aspect of the
forefinger and thumb together with the base of the
forefinger and thumb and the skin web between is
swabbed.
Submitting Firearms Evidence to the
FBI
• Clothing submitted for gunshot residue
examination should be carefully handled, air dried, and wrapped separately in paper.
• Clothin with blood must be air dried and
labeled BIOHAZARD on the inner and outer containers. The date, time, location, collector's name, case number, and evidence
number should be on the container.
Wound Ballistics
Definitions
• Ballistics is the science of the motion of projectiles.
• Interior ballistics is the study of projectiles in
wea ons.• External ballistics is the study of projectiles in
the air.
• Terminal ballistics is the study of projectile
penetration of solids.
• Wound ballistics is the study of projectile
penetration of tissues.
Gunshot WoundsGunshot Wounds
Things for pathologist to
learn:
• type of firearm• distance of gun to victim
• entrance vs. exit wounds
• track of projectile
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Wounding Ballistics
• A moving projectile has kinetic energy proportional to its weight and velocity.
• The wounding effect of a projectile is produced by
transfer of kinetic energy from the projectile to the
.
• The greater the kinetic energy of a projectile, the
greater the wounding potential.
• Kinetic energy increases in proportion to increases in
the velocity squared; hence the great wounding
potential of high velocity projectiles.
Wounding Ballistics
• If a projectile does not exit the body, then all
its kinetic
energy
has
been
transferred
to
the
tissues. If the projectile exits the body, then
transferred to the tissues.
Much of the damage done by a bullet results from the tumbling
motion and the cavitation in the tissue. This is a bullet track in
clay of a .38 caliber round, showing the wound track is larger
than .38 inches (closer to 3 inches).
Wounding Ballistics
• This is an contact gunshot entrance wound.
• Since the barrel contacts the skin, the gases
released by the fired round go into the
‐
shaped laceration.
• Note also the grey‐black discoloration from
the soot, as well as the faint abrasion ring.
The abrasion ring, and a very clear muzzle imprint,
are seen in this contact range gunshot wound.
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A contact range gunshot entrance wound with
grey-black discoloration from the burned powder.
The appearance
of the wounding
characteristics in
the skull is shownin the diagram.
There is bevelin
of the skull
outward away
from the direction
of origin of the
bullet.
The skull surface shows the heavy soot in this contact
range entrance wound, as well as radiating fracture lines.The direction of fire was toward the back of this picture.
This is an intermediate range gunshot entrance
wound. There is powder "tattooing" around the
entrance site.
Wounding Ballistics
• Exit wounds vary considerably in size and
shape because the bullet can be deformed in
its transit through the body.
• There ma
be
no
exit
wound
at
all
if
the
bullet's energy is absorbed by the tissues.
• Some bullets (such a a "hollowpoint") are
designed to deform so that all their energy
will be converted to tissue damage and not exit.
Term Synonyms Cause
Skin defect Permanent cavity Passing of the projectilethrough the skin
Abradedmargin
Abrasion collar,Marginal abrasion,Contusion ring,
Forward motion of bulletindenting the skin andabrading the margin of
.
Micro-tears High velocity centerfirerifle bullets produce theserather than an abrasion
ring.
Grey Ring Contact ring, Bullet
wipe
Lubricant and debris onbullet surface wiped off
onto the wound edge.
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Term Synonyms Cause
Smudging Fouling,Blackening
Deposition of soot frompartially burnt gases.
Tattooing Involuntarytattooing,Stippling,Pe erin
Unburned, partially burnedand burning propellantgrains abrading andembeddin in skin (intermediate/ close/ nearrange shot).
Singeing Branding
Burning
Hot gases from muzzle atclose range
Muzzleimpression
Muzzlecontusion,Muzzle imprint
Skin impact against muzzleproduced by discharge gases ortemporary cavity formation incontact and near contact wounds
Range Muzzle-TargetDistance
Wound Characteristics
Hard Contact Muzzle jammed hardagainst skin
Edges seared by gasesand blackened by soot(baked into skin)
Loose contact Muzzle in light butcomplete contactwith skin.
Soot deposition in bandaround wound (can bewiped off).
Angled orIncomplete
Muzzle at acuteangle to skin orcontacting contouredskin
Variably located seared-blackened contact zoneadjacent to the wound
Angled nearcontact
Muzzle at acuteangle to contouredskin
Eccentric searedblackened zone and largerpaler zone as in angledcontact but widest onsame side as muzzle
Investigating Gunshot Wounds
Scene:
1. Handle the body as little as possible thus avoiding
artifacts and loss of trace evidence.
2. Pa er ba the hands to reserve trace evidence
3. Transport the body in clear plastic sheeting or a
body bag to preserve trace evidence and avoid
contamination.
4. GSR evidence taken as quickly as possible.
Investigating Gunshot Wounds
Autopsy:
1. X‐ray prior to removing clothing.
2. Recover primer residues from hands by acid
(10% nitric) moistened swab or adhesive tape.
3. Examine hands for trace evidence, soot and
propellant grains, and blood spatter.
4. Examine and remove the clothing without
cutting.
Investigating Gunshot Wounds
5. Examine the body, photograph wounds if appropriate, correlate with clothing.
6. Use dissecting microscope to examine
clothin
defects and
wounds
for
soot
and
propellant.
7. Clean the body, photograph and describe the
wounds.
8. Trace the wound tracks and recover the
projectiles.
9. Complete the dissection.
Investigating Gunshot Wounds
Recover:
1. Propellant grains from skin surface or wound track.
2.
Projectile,
taking
care
not
to
scratch
the
surface
by
con ac w a me a ns rumen .
3. A representative sample of shotgun pellets and all
wadding.
4. Blood for grouping and DNA and blood and tissue for
toxicology.
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Investigating Gunshot Wounds
In gunshot wound cases x‐rays should "always"
be performed to answer the questions:1. Is the projectile present?
2. If present, where is the projectile located?
. e pro ec e e x e , are pro ec e ragmen s
present and where are they located?
4. What type of ammunition or weapon was used?
5. What was the path of the projectile?
Gunshot Suicide
• The majority of suicides (including gunshot suicides) do not leave notes.
• A contact
wound
creates
a presumption
of
suicide
rather than accident.
• With rifle and shot un wounds to the trunk the
trajectory may corroborate suicide.
• With the weapon butt on the ground and the body
hunched over it the trajectory is downwards (not upwards).
• Reaching for the trigger with the right hand rotates the body so that the trajectory is right to left (vice
versa if reaching with the left hand).
Gunshot Suicide
• Suicide handgun wounds occur primarily to the head
(80%), the chest (15%) and abdomen (<5%) being
less common.
• Within the head the common sites, in decreasing
, , , of chin and forehead. An unusual location raises a
presumption of homicide.
• Suicidal shotgun wounds show the same site
preference as handguns. Rifle wounds show a
distribution of head 50%, chest 35%, abdomen 15%.
Gunshot Suicide
• Suicide by multiple gunshot is uncommon but not rare.
• A suicide victim may "test fire" the weapon before
inflicting the fatal shot.
• In about 20% of suicides the wea on is found
clutched in the hand.
• Rarely an orange‐brown discoloration of the palm
due to iron deposition from the barrel may be seen; the stain cannot be wiped away.
• Occasionally high velocity impact blood spatter will be deposited on the back of the hand steadying the
muzzle
and
the
back
of
the
firing
hand.
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