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Chapter 21 – Firearms and Tool Marks

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

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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

  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 gunBottom - 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

  13. FRSC 7104 – Chapter 21 Outline • Button Rifling

  14. FRSC 7104 – Chapter 21 Outline • Hammer forged rifling • Electrochemical Rifling

  15. 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

  16. FRSC 7104 – Chapter 21 Outline • Caliber

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

  18. FRSC 7104 – Chapter 21 Outline • Gauge

  19. 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

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

  21. Plain Lead Bullet

  22. FRSC 7104 – Chapter 21 Outline • Forensic Examinations of Firearms • 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.

  23. General Rifling Characteristics Search 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.

  24. FRSC 7104 – Chapter 21 Outline • Bullet Identification

  25. 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.

  26. FRSC 7104 – Chapter 21 Outline • Cartridge Case Identification

  27. FRSC 7104 – Chapter 21 Outline • Striated Action Marks • Chamber Marks

  28. FRSC 7104 – Chapter 21 Outline • Shear Marks

  29. FRSC 7104 – Chapter 21 Outline • Firing Pin Drag Marks • Extractor Marks • Ejector Marks • Impressed Action Marks • Firing Pin Impressions

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

  31. 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

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

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

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

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

  36. FRSC 7104 – Chapter 21 Outline • Gunshot Residue on Hands • GSR Analysis Techniques

  37. FRSC 7104 – Chapter 21 Outline • Bullet Holes • Entrance Wounds • Exit Wounds

  38. FRSC 7104 – Chapter 21 Outline • Toolmark Examinations • Introduction Forged Key Toolmarks Lock Picking Toolmarks

  39. FRSC 7104 – Chapter 21 Outline • Types of Toolmarks • Indentations • Striations

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

  41. FRSC 7104 – Chapter 21 Outline • Collecting and Processing Toolmark Evidence • Photography • Processing at Crime Scene

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

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