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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.


• 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.


• 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.


• 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.


• 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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• 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.


• 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.


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.


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.


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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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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