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FIREARMS EXAMINATIONS (Part 2)

FIREARMS EXAMINATIONS (Part 2). Professor Bensley Alfred State College. Firearms – Bullet Comparisons. Lands and Grooves Caliber. Class characteristics of weapons. Firearms – Bullet Comparisons. Striations = individual characteristics. Firearms - Shotguns.

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FIREARMS EXAMINATIONS (Part 2)

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  1. FIREARMS EXAMINATIONS (Part 2) Professor Bensley Alfred State College

  2. Firearms – Bullet Comparisons Lands and Grooves Caliber • Class characteristics of weapons

  3. Firearms – Bullet Comparisons • Striations = individual characteristics

  4. Firearms - Shotguns • Shotguns - smooth barrel = no impressions on ammo • Shotguns - fire small lead balls or pellets contained within a shotgun shell • Gaugeis diameter of barrel of a shotgun • Example: 12-gauge shotgun has diameter of 0.730 inch

  5. Firearms – Cartridge Casings

  6. How Standards are Collected in the Lab

  7. Automated Firearms Search Systems • NIBIN– National Integrated Ballistics Information Network • Over 11,000 connections have been made to date

  8. Bullet Holes • Why is it important to examine bullet holes? • Entrance Wounds • Usually even margins • Most are slightly smaller than bullet that created them • Can you determine caliber of weapon by examining entrance wound? • Exit Wounds • Usually irregular margins (star shaped) • Often larger in diameter than projectile and entrance wound Why?

  9. JFK Assassination Video

  10. Gunpowder Residues • What causes them? • Can be used in distance estimations

  11. Distance Estimation • Contact wound – dark ring of GSR around entry hole • Close range – 2-12” – visible GSR around entry hole

  12. Distance Estimation • Intermediate Range – 12-24” – wider diameter of GSR – stippling around wound

  13. Gunpowder Residues • What is in GSR? • Griess Test • Test for nitrites • Orange dye produced when nitrites react with Griess reagent

  14. Chemical Tests for GSR • Sodium Rhodizonate test • Test for lead • Bright pink dye produced

  15. Gunpowder Residue on Hands • Can perform chemical tests on wipes from a hand to possibly determine if the person was near a gunwhen it was fired

  16. Serial Number Restoration • Can use chemicals to allow previously obliterated serial numbers on metal to reappear • Oxidation-Reduction Reactions

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