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What is ballistics? Give examples of how ballistics is used in forensic science.

What is ballistics? Give examples of how ballistics is used in forensic science. Introduction. Ballistic evidence helps explain: What type of firearm was used. The caliber of the bullet. The number of bullets fired. Where the shooter was. Whether a weapon was fired recently.

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What is ballistics? Give examples of how ballistics is used in forensic science.

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  1. What is ballistics? Give examples of how ballistics is used in forensic science.

  2. Introduction Ballistic evidence helps explain: • What type of firearm was used. • The caliber of the bullet. • The number of bullets fired. • Where the shooter was. • Whether a weapon was fired recently. • If a firearm was used in previous crimes. Forensic Science: Fundamentals & Investigations, Chapter 17

  3. Firearm Nomenclature Slide Barrel Extractor Trigger Hammer Safety

  4. Ammunition bsapp.com

  5. Bullets, Cartridges, and Calibers Bullets and cartridges are packaged together. The bullet, usually of metal, is out front with the cartridge, holding the primer and propellant powders, behind. Forensic Science: Fundamentals & Investigations, Chapter 17

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  9. Bullet Design • “Bullet” refers to the projectile(s) which actually exits the barrel of the gun when fired • Bullets vary in shape and composition • Most types are variations on three main shapes & three basic compositions bsapp.com

  10. Three Main Shapes bsapp.com

  11. Round Nose • Maximum penetration • Cheapest to manufacture • Easily loads into chambers bsapp.com

  12. Hollow Point • Spreads on impact • Causes additional damage to target • Inhibits penetration bsapp.com

  13. Wad Cutter • Used exclusively as a practice load • Minimizes penetration • Rips a hole in target paper which is visible by the shooter bsapp.com

  14. Three Basic Compositions of Bullets • Lead • ½ Jacketed • Jacketed (Full metal jacket) bsapp.com

  15. Lead • Cheap • Dense • Soft • Easy to mold bsapp.com

  16. ½ Jacketed • A lead bullet coated with copper half way up the exposed portion of the bullet • Used primarily for hollow points • Copper improves exit velocity • Lead promotes mushrooming bsapp.com

  17. Jacketed • A lead bullet completely coated in copper Copper improves exit velocity Used to hold the shape of the bullet in an effort to maximize penetration bsapp.com

  18. Caliber of the Cartridge • Caliber is a measure the diameter of the cartridge in hundredths of an inch. • Common calibers include .22, .25, .357, .38, .44, and .45. • Why should the caliber of ammunition match the firearm that shoots it? If they do not match, what could go wrong? Forensic Science: Fundamentals & Investigations, Chapter 17

  19. What happens to bullets when theyare fired? bsapp.com

  20. Pull the Trigger and . . . • A pin strikes the primer causing a spark. • The powder is then ignited causing an explosion. • This explosion pushesthe bullet down the barrel bsapp.com

  21. Down the Barrel • As a bullet travels down the barrel ,it is twisted by the lands and grooves of the barrel. bsapp.com

  22. Out of the Barrel 5.This rifling causes the bullet to exit in a spiral motion bsapp.com

  23. Bullet Analysis & ComparisonWhat are some characteristics used to identify & compare bullets? bsapp.com

  24. Striations bsapp.com

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  29. Matching Procedure • Fire bullets from a suspected weapon • With the aid of a comparison microscope, compare these “test fires” to the suspected bullets • Striations must be identical for a positive match bsapp.com

  30. Two scopes-One Field ComparisonMicroscope bsapp.com

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  33. What happens to a bullet when it hits a target? • Most bullets tend to mushroom when they hit a target. • Some bullets nearly disintegrate. • Left are bullet fragments from a ½ jacketed hollow point. bsapp.com

  34. Not all bullets mushroom the same. A lot depends on the speed and shape of the bullet, and the characteristics of the target. bsapp.com

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  36. Some more bullets recovered after firing The striations from the rifling are still visible bsapp.com

  37. Gunshot Residues • Chemical testing often can detect gun shot residue even if removal is attempted. • What does this mean for investigation? Forensic Science: Fundamentals & Investigations, Chapter 17

  38. Databases • Like fingerprints, there is a federal database for firearms used in previous crimes – NIBIN (National Integrated Ballistics Network). Forensic Science: Fundamentals & Investigations, Chapter 17

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