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FIREARMS & TOOLMARKS

Gary M. Lind, FA-AFTE

Anthony R. Spadafora, CFWE-IAI

Forensic Scientist

Firearm and Toolmark Section

Footwear and Tire Track Section

FIREARMS & TOOLMARKS

OVERVIEW

• TOOLS AND TOOLMARKS

• FIREARMS, BARRELS, AND BULLETS

• DISTANCE DETERMINATION

• FRACTURE MATCH/PHYSICAL FIT

• SERIAL NUMBER RESTORATION

• NIBIN

• PACKAGING

2/14/2020Northeastern Illinois Regional Crime Laboratory [email protected] 2

TOOLS & TOOLMARKS

TOOL:

THE HARDER OF TWO OBJECTS THAT COMES INTO FORCEFUL CONTACT WITH ONE ANOTHER,

RESULTING IN THE SOFTER OBJECT BEING MARKED.


TOOLS & TOOLMARKS

TOOLMARK:

FEATURES IMPARTED ON AN OBJECT BY THE CONTACT AND FORCE EXERTED FROM A TOOL.

TWO TYPES –

IMPRESSED TOOLMARKS

STRIATED TOOLMARKS


TOOLS & TOOLMARKS

IMPRESSED TOOLMARK:

• FEATURES PRODUCED WHEN A

TOOL CONTACTS AN OBJECT WITH

ENOUGH COMPRESSIVE FORCE

THAT IT LEAVES AN IMPRESSION.


TOOLS & TOOLMARKS

STRIATED TOOLMARK:

• FEATURES PRODUCED WHEN A

TOOL CONTACTS AN OBJECT WITH

LATERAL FORCE AND MOTION.


BULLETS AND BARRELS

• FIREARM BARRELS CAN LEAVE STRIATED TOOLMARKS ON FIRED BULLETS, SHOTGUN WADS,

AND OTHER PROJECTILES.

• RIFLED BARRELS HAVE A SERIES OF LANDS AND GROOVES THAT CAUSE BULLETS TO SPIN,

MAKING THEM STABLE AND ACCURATE IN FLIGHT. RIFLING LEAVES IMPERFECTIONS FOR

IDENTIFICATION ON BULLETS.

• SMOOTHBORE BARRELS CAN STILL POTENTIALLY LEAVE IMPERFECTIONS FOR IDENTIFICATION.


RIFLED VERSUS SMOOTHBORE


RIFLED BARREL TOOMARKS

RIFLING – BARREL DIAMETER, RIFLING

DIRECTION, NUMBER OF LANDS AND

GROOVES, LAND AND GROOVE

WIDTHS, AND MICROSCOPIC

IMPERFECTIONS IMPRESSED INTO

BULLET WHEN FIRED THROUGH

BARREL

RIFLING IS OBSERVED, MEASURED,

AND COMPARED … ON A

COMPARISON MICROSCOPE


COMPARISON

MICROSCOPE

• TWO MICROSCOPES JOINED BY AN

OPTICAL BRIDGE

• SIMULTANEOUS VIEWING OF

EVIDENCE ON LEFT AND RIGHT

SIDE, UNDER MAGNIFICATION

• FIELD OF VIEW IS SEPARATED BY

HAIRLINE

• EXAMINER WILL COMPARE

IMPRESSED AND STRIATED

TOOLMARKS ACROSS THIS HAIRLINE


MICROSCOPIC

FIRED BULLET

COMPARISON

• LEFT AND RIGHT ARE MERGED

IMAGES OF TWO FIRED BULLETS

SEPARATED BY A HAIRLINE

• STRIATED OR IMPRESSED MARKINGS

ARE COMPARED ACROSS THE

HAIRLINE


DISTANCE

DETERMINATION –

GUNPOWDER

PATTERNCAN OPINE APPROXIMATED MUZZLE TO

GARMENT DISTANCE

OBSERVED PATTERN DIAMETER, TEARING, AND BURNING ALONG WITH TEST FIRING

CAN BE USED TO ESTIMATE DISTANCE

INFRARED PHOTOGRAPHY AND/OR

CHEMICAL PROCESSING MAY BE USEFUL TO

ENHANCE PATTERN FOR VISIBILITY

MOST FIREARMS STOP LEAVING A USABLE

PATTERN AT 2 ½ - 3 FEET FROM MUZZLE


INFLUENCE ON GUNPOWDER PATTERNS

• INTERVENING OBJECTS

• ADHESION OF POWDER PATTERN TO EVIDENCE ITEM

• MOVEMENT OF EVIDENCE ITEM

• AMMUNITION VARIABLES (POWDER TYPE, PRIMER TYPE, NON-TOXIC)

• OTHERS?


DISTANCE DETERMINATION –

SHOT PATTERN• THE APPROXIMATE PATTERN

DIAMETER IS MEASURED AND

EXAMINED FOR PELLET

DISTRIBUTION

• USUALLY, THE PATTERN SPREADS

ABOUT 1 INCH PER 3 FEET

DISTANCE FROM MUZZLE

(SMOOTHBORE BARREL)

• HOWEVER, AMMO, CHOKE,

MUZZLE CROWN, AND BARREL

TYPE CAN CAUSE UNUSUAL

THINGS…


EXAMPLE PATTERN

• TEST PATTERN DIAMETER ABOUT

3 INCHES AT 9 FEET

• AGREEMENT OF 1 INCH OF

SPREAD PER 3 FEET DISTANCE

FROM MUZZLE


FRACTURE MATCH/PHYSICAL FIT

• CAN DETERMINE IF TWO ITEMS AT

ONE TIME FORMED A SINGLE

OBJECT

• BULLET FRAGMENTS

• CAR PARTS

• BIKE HELMETS

• KNIVES

• ETC.


SERIAL NUMBER

RESTORATION

• SERIAL NUMBERS ARE STAMPED

INTO FIREARMS

• THE STAMPS USED CREATE A MORE

DENSE AREA OF METAL BELOW THE

CHARACTERS

• SOMETIMES THE SERIAL NUMBERS

ARE REMOVED VIA SCRATCHING

OR GRINDING


SERIAL NUMBER

RESTORATION

• SURFACE POLISHING AND ACID

ETCHING ARE USED TO RECOVER

THE SERIAL NUMBER.

• THE ACID WILL DISSOLVE THE LESS

DENSE METAL FASTER THAN THE

MORE DENSE METAL BELOW THE

CHARACTERS, THUS “RAISING” ASERIAL NUMBER

• SUCCESSFUL RESTORATION

DEPENDENT ON HOW FAR THE

CHARACTERS ARE OBLITERATED.


DIGITAL IMAGING SYSTEM THAT CAN CAPTURE AND SORT IMAGES OF EVIDENCE AND

TEST FIRED CARTRIDGE CASES IN AN ATTEMPT TO DEVELOP INVESTIGATIVE LEADS

(HITS) BASED ON SIMILARITY OF THE IMAGES.


WHAT DOES NIBIN DO?

• DATABASE SEARCH FOR SIMILAR IMAGES

• ABILITY TO SEARCH ANY OTHER NIBIN SITE

NATIONWIDE

• DEVELOPS INVESTIGATIVE LEADS (NIBIN HITS)

BASED ON SIMILARITY OF IMAGES

• NOTIFICATION OF INVESTIGATIVE LEADS SENT

TO AFFECTED AGENCIES WITHIN 24 HOURS


INVESTIGATIVE LEADS – CONFIRMED VIA LAB

EXAMINATION

• A NIBIN HIT OR MATCH IS CONSIDERED A PRESUMPTIVE TEST, NOT A CONFIRMATION OF

IDENTIFICATION

• IF AN INVESTIGATIVE LEAD – NIBIN HIT - IS DEVELOPED, THAT EVIDENCE CAN BE SENT TO A

LABORATORY FOR CONFIRMATION THROUGH MICROSCOPIC IDENTIFICATION

• REPORT ISSUED DETAILING RESULTS OF MICROSCOPIC COMPARISON


FIREARM PACKAGING

• ONE FIREARM PER PACKAGE

• EJECTION PORT OF CHAMBER VISIBLE, IF POSSIBLE

• NO OBJECTS THROUGH BARREL (ZIP-TIES, WIRE, ETC.)

• NO LOOSE AMMUNITION IN PACKAGE


FIRED EVIDENCE PACKAGING

• ONE FIRED BULLET OR DISCHARGED CARTRIDGE CASING PER

PACKAGING

• SUBMIT MANY SMALLER ENVELOPES IN A LARGER PACKAGE

• HAVE MEDICAL EXAMINER RINSE AUTOPSY BULLETS PRIOR TO

PACKAGING

• AIR DRY ANY BIOHAZARDOUS ITEMS PRIOR TO SEALING IN

PACKAGE


TOOL PACKAGING

• PROTECT WORKING ENDS OF TOOLS PRIOR TO PACKAGING

• SUBMIT ONE TOOL PER PACKAGE

• ALWAYS SUBMIT QUESTIONED TOOLMARKS SEPARATE FROM

SUSPECT TOOLS


QUESTIONS?

[email protected]

847-362-0676 X 153

WWW.NIRCL.ORG


mailto:[email protected]

THANK YOU!

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