1. Firearms, Tool Marks, and Other Impressions
Objectives:
Describe techniques for rifling a barrel.
List the class and individual characteristics of bullets and cartridge cases.
Explain the utilization of the comparison microscope for the comparison of bullets and cartridge cases.
Distinguish caliber from gauge.
Created by C. Ippolito April 2008
12/3/2018

2. Firearms Identification
concerned with determining whether a bullet or cartridge was fired by a particular weapon
bullet  gun
structural variations
irregularities
scratches & nicks
breaks & wear
more than bullet comparisons
weapons operation
restore obliterated serial numbers
detect & characterize GSR
determine muzzle-to-target distance
Even 4 4/3
Created by C. Ippolito April 2008
12/3/2018

3. Gun Barrel Manufacture
made from solid bar
hollowed by drill
random marks left
followed by rifling
grooves on inner surface
“twist” bullet for straighter, more accurate path
rifling methods
hook cutters – rotated – forms spiral groove – 1 at a time
broach cutter – concentric rings – simultaneous cuts all
button process – metal plug compresses sides
mandrel process – barrel hammer from outside down
Created by C. Ippolito April 2008
12/3/2018

4. Gun Barrel Terms Bore Rifling Groove Land Caliber
the cavity inside the barrel
Rifling
spiral grooves in bore
spins projectile
Groove
cut/low-lying parts of rifled bore
Land
uncut/raised parts of rifled bore
Caliber
diameter of the bore
hundredths of an inch (.22)
millimeters (9mm)
Created by C. Ippolito April 2008
12/3/2018

5. Bullet Markings Class Characteristics
lands
grooves
twist direction
General Rifling Characteristic File
FBI data base of class characteristics
Individual Characteristics
striations
fine lines caused
minute imperfections on cutters
steel chips from cutters
Comparison Microscope
tool used to compare bullets
Created by C. Ippolito April 2008
12/3/2018

6. Shotgun Barrel smooth bore gauge groove would spread pellets
diameter of barrel
# of lead balls with diameter = to bore of barrel that would weigh 1 lb
Created by C. Ippolito April 2008
12/3/2018

7. Comparison of Cartridge/Shotgun Shell
Created by C. Ippolito April 2008
12/3/2018

8. Cartridge/Shell Markings
Breechblock
rear part of barrel
marks base of cartridge/shell
Firing Pin
strike mark on base of cartridge/shell
Ejector/Extractor
mechanism that removes cartridge/shell from chamber
leaves unique striations
Created by C. Ippolito April 2008
12/3/2018

9. Firearms, Tool Marks, and Other Impressions
Objectives:
Explain the NIBIN data test system.
Explain the procedure for determining at what distance from a target a weapon was fired.
Describe the laboratory tests utilized for determining whether an individual has fired a weapon. Emphasize the limitations of the present techniques.
Explain why it may be possible to restore an obliterated serial number.
Created by C. Ippolito April 2008
12/3/2018

10. Automated Firearm Search Systems
DRUGFIRE (FBI)
unique markings on cartridge cases
microscope images captured and digitalized
Integrated Ballistic Identification System (ATF)
Bulletproof
bullet analyzing module
Brasscatcher
cartridge analyzing module
National Integrated Ballistic Identification System
1999 the two systems combined
Created by C. Ippolito April 2008
12/3/2018

11. Gunpowder Residues Distance determination Handguns and Rifles
distribution of powder/pellets
calculate firearm distance from target
Handguns and Rifles
1” or less
heavy smoke stains
loose fibers/melted fibers
star-shaped tear surrounded by smoke
12”-18”
halo of smoke stain
25”-36”
scattered gunpowder particles
ball powder cartridges can extend to 6’-8’
> 3’
bullet wipe
carbon, dirt, lubricant which wipes off surface of bullet
Created by C. Ippolito April 2008
12/3/2018

12. GSR Patterns
Created by C. Ippolito April 2008
12/3/2018

13. GSR Patterns 3” 9” 15” 21” Greiss test Sodium rhodizonate Test
shows nitrites
Sodium rhodizonate Test
turns lead particles pink then violet
Created by C. Ippolito April 2008
12/3/2018

14. Primer Residues Dermal Nitrate Test Primer Test
paraffin wax treated w/diphenylamine
blue color w/nitrates
Primer Test
looks for:
lead styphate
barium nitrate
antimony sulfate
SEM Testing
Neutron Activation Analysis
Atomic Absorptive Spectrophotometry
Created by C. Ippolito April 2008
12/3/2018

15. Serial Number Restoration
detects strain in metal crystals
can be “re-etched”
HCl + copper chloride + water for steel
Created by C. Ippolito April 2008
12/3/2018

16. Firearms, Tool Marks, and Other Impressions
Objectives:
List procedures for the proper collection and preservation of firearm evidence.
Explain how a suspect tool is compared to a tool mark.
Explain the forensic significance of class and individual characteristics to the comparison of impressions.
List some common field reagents used to enhance bloody footprints.
Created by C. Ippolito April 2008
12/3/2018

17. Collection & Preservation of Firearms
Safety – unload any ammo
note hammer/safety position
note location of fired/unfired ammo
Revolver
note chamber position
note cartridge/casing in chamber w/position
each round in own box
Automatic
remove magazine – test for prints
Water recovery
ship weapon with water covering weapon
Created by C. Ippolito April 2008
12/3/2018

18. Collection and Preservation of Ammo
Must save class/individual markings
free bullets by breaking away material
use only plastic tools
scribe with initials
leave trace materials on bullet
paint, fibers, etc.
Created by C. Ippolito April 2008
12/3/2018

19. Tool Marks indented impressions class characteristic
all tools show microscopic irregularities from their manufacturing
indented impressions individual characteristics
microscopic irregularities from damage and wear
Created by C. Ippolito April 2008
12/3/2018

20. Preserving Impressions
photograph
Lifting Impressions in Dust/Dirt
electrostatic lifting device
Casting Impressions
dental stone (gypsum)
Snow Impression Wax
Created by C. Ippolito April 2008
12/3/2018