Syracuse University
June, 2010
Firearms and Toolmarks
Forensic Firearm Analysis
WALLIE HOWARD JR.
CENTER FOR FORENSIC SCIENCES
Matthew Kurimsky
Firearms Examiner
FORENSIC FIREARMS
IDENTIFICATION
• A scientific process of determining whether
a bullet or cartridge case was fired from a
particular weapon. This is done by
examining and evaluating the class and
individual characteristics imparted onto the
bullet or cartridge case.
FIREARMS SECTION
•
•
•
•
•
•
•
FIREARM IDENTIFICATION
OPERABILITY ANALYSIS
FIREARM COMPARISONS
PHYSICAL MATCH COMPARISONS
IBIS ENTRIES
SERIAL NUMBER RESTORATION
GUNSHOT RESIDUE DISTANCE
DETERMINATION
FIREARMS IDENTIFICATION
• Can determine the general condition of a
firearm and whether the firearm is
mechanically functional.
• Can determine whether the firearm was
altered to fire in full-automatic mode.
• Can be test fired to obtain known specimens
for comparison to evidence ammunition
components.
HOMEMADE
CLASS CHARACTERISTICS
• Are measurable features of a specimen that
indicate a restricted group source.
• Result from design factors, and are
determined prior to manufacture.
• Examples are firing pin shape, caliber, and
general rifling characteristics.
BREECH FACE
Breech face of a
firearm.
Arch breech face
marks.
RIFLING
• Helical grooves in the
bore of a firearm
barrel to impart rotary
motion to a projectile.
Rifling
COMMON TYPES OF RIFLING
• BROACH RIFLING:
Cuts the grooves by being
pushed or pulled through
the barrel while being
rotated.
• BUTTON RIFLING:
Pushed or pulled through a
drilled and reamed barrel
so as to cold form the
spiral grooves to the
desired depth and twist.
NOT a cutting process.
GENERAL RIFLING
CHARACTERISTICS
• The number, width and
direction of twist of the
rifling grooves in a
barrel of a given caliber
firearm.
INDIVIDUAL
CHARACTERISTICS
• Marks produced by the random imperfections
or irregularities of tool surfaces.
• These random imperfections or irregularities
are produced incidental to manufacture
and/or caused by use, corrosion, or damage.
• They are unique to that tool and distinguish it
from all other tools.
COMPARISON MICROSCOPE
• Optically bridged so objects
can be viewed side by side.
CARTRIDGE CASE OR
SHOTSHELL EXAMINATION
• Cartridge case examination can determine
the caliber or gauge, and the manufacturer.
• The images of questioned cartridge cases can
be entered into IBIS to compare with
evidence from other shooting incidents.
• The microscopic characteristics of evidence
cartridge cases can be examined to determine
whether they were fired in a specific firearm.
CARTRIDGE CASING
IDENTIFICATION
Parallel breech face marks.
Granular breech
face marks.
Circular breech face
marks.
FIRING PIN
Firing pin
impression.
Firing pin drag
mark.
OTHER MARKS
Ejector marks.
Extractor marks.
BULLET EXAMINATIONS
• Bullets can be examined to determine the
general rifling characteristics.
• 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.
SHOOTING TANK
Bullet comparisons
The gun barrel is produced from a solid bar of
steel that has been hollowed out by drilling
The microscopic drill marks left on the barrel
inner surface are randomly irregular and would
in themselves serve to impart a uniqueness to
each barrel.
Manufacturers make the inner surface of the
barrel with spiral groves, a step known as rifling
Bullet comparisons
Why rifling in a barrel?
Prevents the bullet from tumbling when it
leaves the barrel, more accuracy.
Bullet comparisons
The diameter of the gun barrel is measured
between opposite lands, this is known as the
caliber of the weapon. It is usually expressed in
hundredths of an inch (.22) or millimeters
(9mm)
Caliber - the diameter of the bore of a rifled
firearm.
Bullet comparisons
Every firearms manufacturer chooses a rifling
process that is best suited to meet the
production standards and requirements of its
product.
Once the choice is made, the class
characteristics of the weapons barrel will
remain consistent; each will have the same
number of lands and grooves, the same
approximate width and directions of twist.
Bullet comparisons
Ex:
.32 caliber Smith & Wesson revolvers have five
lands and grooves twisting to the right
Ex:
.32 caliber Colt revolvers exhibit six lands and
grooves twisting to the left
Bullet comparisons
There are fine lines or striations, many running
the length of the barrel’s lands and grooves.
These are caused by minute imperfections
found on the rifling cutter’s surface or they are
produced by minute chips of steel pushed
against the barrel’s inner surface.
The fact is that the random distribution and
irregularities of these markings are impossible
to duplicate exactly in any two barrels.
Bullet comparisons
No two rifled barrels, even those manufactured
in succession, will have identical striation
markings!
These striations form the individual
characteristics of the barrel.
The number of lands and grooves, and their
direction of twist are obvious points of
comparison during initial stages of the
examination
Bullet comparisons
By comparing the lands and grooves and
directions of twist, we can eliminate certain
weapons.
The most important tool for the firearms
examiner is the comparison microscope.
COMARISON MICROSCOPE
Bullet comparisons
The striations of the bullet are lined up and
compared
BULLET IDENTIFICATION
Bullet comparisons
With shotguns, most barrels are smooth
The diameter of the shotgun barrel is expressed
by the term gauge
Gauge - the number of lead balls with the same
diameter as the barrel that would make a pound
ex: 20 ga = diameter of lead ball weighing
1/20th of a pound
Exception to this is 410 gauge, actually is .410 inch diameter
PHYSICAL MATCH
COMPARISON
• Physical match comparison can determine
whether evidence was joined together and
subsequently broken apart.
Projectile jacket
separation.
Copper jacket
fragment.
MATCH
Fragment match.
Stria match.
INTEGRATED BALLISTICS
IDENTIFICATION SYSTEM (IBIS)
• Images of projectiles and
cartridge casings
recovered from the crime
scene, or produced from
evidence weapons are
entered into the database
and searched.
• Used to link multiple
crimes to a single
weapon.
• Potential hits are
compared to one
another by a
firearms examiner
on a comparison
microscope.
• Hits are NOT made
by simply looking
at the images in
IBIS.
SHOT PELLETS, BUCK
SHOT, OR SLUGS
• Examination of shot pellets, buck shot, or
slugs can determine the size of the shot or
the gauge of the slug, and the manufacturer.
SHOTSHELL COMPONENTS
00 BUCK
WADDING EXAMINATIONS
• Examinations of
wadding
components can
determine the
gauge and the
manufacturer.
UNFIRED CARTRIDGES OR
SHOTSHELLS
• 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.
SERIAL NUMBER
RESTORATIONS
• Obliterated and/or altered firearm serial
numbers can sometimes be restored.
• Chemical, electrolytic, and magnetic
particle inspection are some of the methods
used.
Before restoration.
After restoration.
FIRING RANGE
Gunpowder residues
The accuracy of a distance determination
varies according to the circumstances of the
case
Because the spread and density of the
residue pattern will vary widely between
weapons and ammunition.
Gunpowder residues
A COMPARISON IS
SIGNIFICANT ONLY WHEN IT
IS MADE WITH THE SUSPECT
WEAPON AND AMMUNITION
OR AMMUNITION OF THE
SAME MAKE AND TYPE
Contact Pattern Shotgun
Gunpowder residues
Items that influence estimating target
distance (amt. Of gunpowder residue)
Barrel length
Caliber
type of ammunition
Type and condition of the weapon fired
Gunpowder residues
Tests done on garments in the lab
Examine microscopically for presence
of gunpowder residue
Nitrite test - greis test
Sodium rhodizoante test (lead)
Greis test - a chemical test to develop patterns of
gun powder residues around bullet holes
Victims Clothing
3 inch Test Pattern
DISTANCE DETERMINATION
SODIUM RHODIZONATE TEST
• Tests for the
presence of lead.
• Converts lead to
lead rhodizonate.
GRIESS TEST
• Tests for the
presence of
nitrites.
• Converts nitrites
to nitrates.
PRIMER RESIDUE ON HANDS
GSR
During the firing process.
GSR particle.
Toolmarks
Defined as any impression, cut, gouge, or abrasion
caused by a tool coming into contact with another
object
USUALLY THERE WILL BE
CLASS CHARACTERISTICS
SIZE
SHAPE
Toolmarks
Sometimes nicks and wear patterns will
individualize a tool
INDIVIDUAL CHARACTERISTICS ARE
HARD TO IDENTIFY BECAUSE OF
THE DIFFICULTY OF DUPLICATING
THE TOOL MARK IN THE LAB
Toolmarks
Toolmarks
UNDER NO CIRCUMSTANCE
MUST THE CRIME SCENE
INVESTIGATOR ATTEMPT TO FIT
THE SUSPECT TOOL INTO THE
TOOL MARK
Toolmarks
BEAR IN MIND THAT THE TOOL
OR IMPRESSION MAY CONTAIN
VALUABLE TRACE EVIDENCE
QUESTIONS?
Matthew Kurimsky – Firearms
Examiner
matthewkurimsky@ongov.net
315-435-3800 firearms unit