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Chapter 21 – Firearms and Tool Marks

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1 Chapter 21 – Firearms and Tool Marks
FRSC 7104 Criminalistics I Professor Bensley

2 FRSC 7104 – Chapter 21 Objectives
After 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

3 FRSC 7104 – Chapter 21 Outline Introduction Total 14,916 14,224 13,752
FBI Uniform Crime Reports (2011) Murder Victims by Weapon, 2007–2011 2007 2008 2009 2010 2011 Total 14,916 14,224 13,752 13,164 12,664 Total firearms: 10,129 9,528 9,199 8,874 8,583 (68%) (67%) Handguns 7,398 6,800 6,501 6,115 6,220 Rifles 453 380 351 367 323 Shotguns 457 442 423 366 356 Other guns 116 81 96 93 97 Firearms, 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 1,694 Blunt objects (clubs, hammers, etc.) 647 603 623 549 496 Personal weapons (hands, fists, feet, etc.)1 869 875 817 769 728 Poison 10 9 7 11 5 Explosives 1 2 4 12 Fire 131 85 98 78 75 Narcotics 52 34 45 29 Drowning 16 8 15 Strangulation 134 89 122 Asphyxiation 109 87 84 Other weapons or weapons not stated 1,005 999 904 872 853 1 Pushed is included in personal weapons.

4 FRSC 7104 – Chapter 21 Outline Firearm Examinations Types of Firearms
Handguns Revolvers Single action Double action

5 FRSC 7104 – Chapter 21 Outline Semi-automatic pistols

6 FRSC 7104 – Chapter 21 Outline Rifles (Shoulder arms)

7 FRSC 7104 – Chapter 21 Outline Semi-automatic Automatic Machine Guns
Submachine Guns

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

9 FRSC 7104 – Chapter 21 Outline Shotguns

10 FRSC 7104 – Chapter 21 Outline Firearm Construction

11 FRSC 7104 – Chapter 21 Outline Rifling Lands and Grooves

12 FRSC 7104 – Chapter 21 Outline Broach rifling

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15 FRSC 7104 – Chapter 21 Outline Button Rifling

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17 FRSC 7104 – Chapter 21 Outline Hammer forged rifling
Electrochemical Rifling

18 Bullet Impressions Left - A bullet fired from a conventional 6/right rifled barrel Right – 40 Caliber bullet with polygonal rifling impressions like those seen on the 40 caliber bullet

19 FRSC 7104 – Chapter 21 Outline Caliber

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

21 FRSC 7104 – Chapter 21 Outline Gauge

22 FRSC 7104 – Chapter 21 Outline Firearm Ammunition Bullets
7.62x39mm caliber armor piercing bullets 9mm LUGER caliber FEDERAL "Hydra-shok" bullet 32 S&W LONG caliber plain lead bullet

23 FRSC 7104 – Chapter 21 Outline Video of Firing Action in a Firearm
Propellants Primers Cartridge Cases Shot shells Video of Firing Action in a Firearm

24 Plain Lead Bullet

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28 FRSC 7104 – Chapter 21 Outline Forensic Examinations of Firearms
Class vs. Individual Characteristics Land Impressions: Left AUTO caliber FMJ bullets fired from a EAA Corp. pistol Right - 9mm LUGER caliber FMJ bullets fired from a BROWNING pistol.

29 General Rifling Characteristics Search
CARTRIDGE MANUFACTURER TWIST L&G LAND GROOVE 9MM LUGER AA ARMS INC R 6 .055 .120 ASTRA .053 .128 BERETTA .130 HI-POINT FIREARMS INTERDYNAMIC .124 LLAMA .054 MAUSER SMITH & WESSON .056 .122 STAR .126 SWD INC 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 tolerance and the results of the search would look something like the data contained in the above table.

30 FRSC 7104 – Chapter 21 Outline Bullet Identification

31 Bullet Fragments Image below shows the bullet fragments from left compared to a known standard bullet. Standard is on the left side of the comparison below.

32 FRSC 7104 – Chapter 21 Outline Cartridge Case Identification

33 FRSC 7104 – Chapter 21 Outline Striated Action Marks Chamber Marks

34 FRSC 7104 – Chapter 21 Outline Shear Marks

35 FRSC 7104 – Chapter 21 Outline Firing Pin Drag Marks Extractor Marks
Ejector Marks Impressed Action Marks Firing Pin Impressions

36 FRSC 7104 – Chapter 21 Outline NIBIN Breech Marks Ejector Marks
Breech face of 12 gauge shotgun and photomicrograph of cartridge case fired from the same weapon. Ejector Marks NIBIN

37 Fun Movies http://www.youtube.com/watch?v=DaXcXVvRuJ8&feature=related

38 FRSC 7104 – Chapter 21 Outline Gunshot (Gunpowder) Residue
What causes gunpowder residue?

39 FRSC 7104 – Chapter 21 Outline Distance Estimations (Determinations)
Ranges of fire Contact Near-contact Intermediate Distant 3” 6” 12” 24” 36”

40 FRSC 7104 – Chapter 21 Outline Powder Residue Detection Methods Visual
Chemical Griess Test (Modified Griess Test)

41 FRSC 7104 – Chapter 21 Outline Sodium Rhodizonate
1. Untreated 12 inches 3. Greiss followed by Sodium Rhodizonate 2. Greiss Test 12 inches

42 FRSC 7104 – Chapter 21 Outline Gunshot Residue on Hands
GSR Analysis Techniques

43 FRSC 7104 – Chapter 21 Outline Bullet Holes Entrance Wounds
Exit Wounds

44 FRSC 7104 – Chapter 21 Outline Toolmark Examinations Introduction
Forged Key Toolmarks Lock Picking Toolmarks

45 FRSC 7104 – Chapter 21 Outline Types of Toolmarks Indentations
Striations

46 FRSC 7104 – Chapter 21 Outline Class vs. Individual Characteristics in Toolmarks Unusual Toolmark Types

47 FRSC 7104 – Chapter 21 Outline Collecting and Processing Toolmark Evidence Photography Processing at Crime Scene

48 FRSC 7104 – Chapter 21 Outline Trace Evidence Processing in the lab
Cast vs. Mold Lab Examinations


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