Chapter 21 – Firearms and Tool Marks

FRSC 7104Criminalistics I

Professor Bensley

FRSC 7104 – Chapter 21 ObjectivesAfter studying this chapter, the student should be able to: Recognize the various types of firearms and their basic

components Recognize the various types of ammunition and their

uses Understand how firearms evidence is collected and

analyzed Describe the basic details of tool mark comparisons and

firing distance determinations

FRSC 7104 – Chapter 21 OutlineI. Introduction

FBI Uniform Crime Reports (2011) Murder Victims

by Weapon, 2007–2011

2007 2008 2009 2010 2011Total 14,916 14,224 13,752 13,164 12,664Total firearms: 10,129 9,528 9,199 8,874 8,583

(68%) (67%) (67%) (67%) (68%)Handguns 7,398 6,800 6,501 6,115 6,220Rifles 453 380 351 367 323Shotguns 457 442 423 366 356Other guns 116 81 96 93 97Firearms, type not stated 1,705 1,825 1,828 1,933 1,587

Knives or cutting instruments 1,817 1,888 1,836 1,732 1,694Blunt objects (clubs, hammers, etc.) 647 603 623 549 496

Personal weapons (hands, fists, feet, etc.)1 869 875 817 769 728Poison 10 9 7 11 5Explosives 1 11 2 4 12Fire 131 85 98 78 75Narcotics 52 34 52 45 29Drowning 12 16 8 10 15Strangulation 134 89 122 122 85Asphyxiation 109 87 84 98 89Other weapons or weapons not stated 1,005 999 904 872 8531 Pushed is included in personal weapons.

FRSC 7104 – Chapter 21 Outline

II. Firearm ExaminationsA. Types of Firearms

1. Handgunsa. Revolvers

i. Single actionii. Double action

FRSC 7104 – Chapter 21 Outlineb. Semi-automatic pistols

FRSC 7104 – Chapter 21 Outline

2. Rifles (Shoulder arms)

FRSC 7104 – Chapter 21 Outlinea. Semi-automaticb. Automaticc. Machine Gunsd. Submachine Guns

Top - .50 caliber M2 machine gunBottom - Heckler & Koch MP5 submachine gun

FRSC 7104 – Chapter 21 Outline

3. Shotguns

FRSC 7104 – Chapter 21 OutlineB. Firearm Construction

FRSC 7104 – Chapter 21 Outline1. Rifling

a. Lands and Grooves

FRSC 7104 – Chapter 21 Outlineb. Broach rifling

FRSC 7104 – Chapter 21 Outlinec. Button Rifling

FRSC 7104 – Chapter 21 Outlined. Hammer forged rifling

e. Electrochemical Rifling

Bullet Impressions

Left - A bullet fired from a conventional 6/right rifled barrelRight – 40 Caliber bullet with polygonal rifling impressions like those seen

on the 40 caliber bullet

FRSC 7104 – Chapter 21 Outline2. Caliber

Caliber

Left to Right:.50 caliber down to .22 caliber

FRSC 7104 – Chapter 21 Outline3. Gauge

FRSC 7104 – Chapter 21 OutlineC. Firearm Ammunition

1. Bullets

32 S&W LONG caliber plain lead bullet

9mm LUGER caliber FEDERAL "Hydra-shok" bullet

7.62x39mm caliber armor piercing bullets

FRSC 7104 – Chapter 21 Outline

2. Propellants3. Primers4. Cartridge Cases5. Shot shells

Video of Firing Action in a Firearm

Plain Lead Bullet

FRSC 7104 – Chapter 21 OutlineD. Forensic Examinations of Firearms

1. Class vs. Individual Characteristics

Land Impressions: Left - 380 AUTO caliber FMJ bullets fired from a EAA Corp. pistol Right - 9mm LUGER caliber FMJ bullets fired from a BROWNING pistol.

General Rifling Characteristics SearchCARTRIDGE MANUFACTURER TWIST L&G LAND GROOVE

9MM LUGER AA ARMS INC R6 .055 .120

9MM LUGER ASTRA R 6 .053 .128

9MM LUGER BERETTA R 6 .055 .130

9MM LUGER HI-POINT FIREARMS R 6 .055 .120

9MM LUGER INTERDYNAMIC R 6 .055 .124

9MM LUGER LLAMA R 6 .054 .120

9MM LUGER MAUSER R 6 .054 .128

9MM LUGER SMITH & WESSON R 6 .056 .122

9MM LUGER STAR R 6 .054 .126

9MM LUGER SWD INC R 6 .055 .120

9mm LUGER bullet, fired from a 6/right rifled barrel, with a land width of .055mm and a groove width of .125mm. Firearm examiners will usually search with a plus or minus .003-.005 tolerance and the results of the search would look something like the data contained in the above table.

FRSC 7104 – Chapter 21 Outline

2. Bullet Identification

Bullet FragmentsImage below shows the

bullet fragments from left compared to a known standard bullet. Standard is on the left side of the comparison below.

FRSC 7104 – Chapter 21 Outline3. Cartridge Case Identification

FRSC 7104 – Chapter 21 Outlinea. Striated Action Marks

i. Chamber Marks

FRSC 7104 – Chapter 21 Outlineii. Shear Marks

FRSC 7104 – Chapter 21 Outlineiii. Firing Pin Drag Marksiv. Extractor Marksv. Ejector Marks

b. Impressed Action Marksi. Firing Pin Impressions

FRSC 7104 – Chapter 21 Outlineii. Breech Marks

Breech face of 12 gauge shotgun and photomicrograph of cartridge case fired from the same weapon.

iii. Ejector Marks

E. NIBIN

Fun Movies• http://www.youtube.com/watch?v=DaXcXVvRuJ8&feature=related• http://www.youtube.com/watch?v=emP5D9Klssg&feature=related• http://www.youtube.com/watch?v=7PD9EmX7R3I

FRSC 7104 – Chapter 21 OutlineIII. Gunshot (Gunpowder) Residue

A. What causes gunpowder residue?

FRSC 7104 – Chapter 21 Outline

B. Distance Estimations (Determinations)1. Ranges of fire

a. Contactb. Near-contactc. Intermediated. Distant

3” 6” 12”

24” 36”

FRSC 7104 – Chapter 21 Outline

C. Powder Residue Detection Methods1. Visual2. Chemical

a. Griess Test (Modified Griess Test)

FRSC 7104 – Chapter 21 Outlineb. Sodium Rhodizonate

1. Untreated 12 inches

2. Greiss Test 12 inches 3. Greiss followed by Sodium Rhodizonate

FRSC 7104 – Chapter 21 OutlineD. Gunshot Residue on Hands

E. GSR Analysis Techniques

FRSC 7104 – Chapter 21 Outline

F. Bullet Holes1. Entrance Wounds2. Exit Wounds

FRSC 7104 – Chapter 21 OutlineIV. Toolmark Examinations

A. Introduction

Forged Key Toolmarks

Lock Picking Toolmarks

FRSC 7104 – Chapter 21 Outline

B. Types of Toolmarks1. Indentations2. Striations

FRSC 7104 – Chapter 21 Outline

C. Class vs. Individual Characteristics in ToolmarksD. Unusual Toolmark Types

FRSC 7104 – Chapter 21 Outline

E. Collecting and Processing Toolmark Evidence1. Photography

2. Processing at Crime Scene

FRSC 7104 – Chapter 21 Outline

3. Trace Evidence

4. Processing in the laba. Cast vs. Mold

5. Lab Examinations