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BALLISTICS

BALLISTICS. The big picture of ballistics. Because every contact leaves a trace (Locard ’ s exchange principle) very hard contacts (like a 180 mps to 1500 mps contact) will leave a big trace. History of Gunpowder and Firearms. The Chinese invented gunpowder over a thousand years ago.

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BALLISTICS

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  1. BALLISTICS

  2. The big picture of ballistics Because every contact leaves a trace (Locard’s exchange principle) very hard contacts (like a 180 mps to 1500 mps contact) will leave a big trace

  3. History of Gunpowder and Firearms • The Chinese invented gunpowder over a thousand years ago. • Muzzle-loading matchlocks used wicks to ignite the gunpowder. • The cartridge and breech loading followed. • Rifling provided greater accuracy. • Revolver, semi-automatic, and automatic handguns were developed.

  4. Ballistics • The study of projectiles, trajectories, and the effect on the target • Firearms Identification • A sub-discipline of ballistics that determining whether a bullet or cartridge was fired by a particular weapon

  5. 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.

  6. A Internal ballistics What happens in the weapon B External ballistics What happens after the bullet leaves the barrel C Terminal ballistics (wound ballistics) What happens when the bullet hits the target

  7. A Internal ballistics (1 of 3) INTERNAL BALLISTICS

  8. SO WHAT’S A CARTRIDGE? • a combination of: • a projectile (the bullet) • a propellant (gunpowder, for example) • a primer (the explosive cap), A

  9. Cartridges Design The bullet, usually made of metal, is out front with the cartridge, holding the primer and propellant powders, behind.

  10. Watch this short video • http://www.youtube.com/watch?v=c1VD1D1hLsQ

  11. How a gun Works • The firing pin hits the base of the cartridge, igniting the primer powder. • The primer powder sparks through the flash hole to the main propellant supply. • The pressure of the explosion pushes the bullet from the case into the barrel. • The bullet follows the lands and grooves spiraling out of the barrel.

  12. Land = highGroove = Low • BACK OF BULLET

  13. A BROACH CUTTER USED TO CREATE RIFFLING IMPRESSIONS IN A BARREL

  14. As a result of rifling, a barrel will impress a negative impression of itself on the sides of the bullet like those seen below.  A

  15. Matching impressions A

  16. A fired bullet as class evidence • Different gun manufacturers use different rifling techniques. These techniques impart the class characteristics on a fired bullet. • Number of impressions • Width of impressions • Depth of impressions • Angle of impressions

  17. Q: How are these 2 guns different A: caliber

  18. A What is caliber? • Caliber = the diameter of the bullet. • Measured in hundredths of an inches. • .22, .357, or .50 • Measured in metrics • 9mm Question: Why should the caliber of ammunition match the firearm that shoots it? If they do not match, what could go wrong?

  19. Showing variation within caliber

  20. INTERNAL BALISTICS (2 OF 3) BREECH MARKS ARE FOUND ON THE REAR OF A FIRED CARTRIDGE A

  21. A

  22. Firing pin Breech

  23. A

  24. When a bullet is fired, the explosion forces: • the bullet down barrel • the cartridge back against breech • Leaving a negative impression on the back of the cartridge

  25. Depending on the make of gun & normal wear and tear, the breech markings will pick up class, and hopefully, individual characteristics.

  26. Examples of breech markings

  27. How CSI determines if a recovered bullet from a crime scene came from a suspected gun Disclaimer: this video is oooooold • http://www.youtube.com/watch?v=3EJrbpg43qM

  28. Shotguns have smooth barrels with no rifling. • Are there lands or groves on the bullet(s)? • How can a F.S. identify trace evidence left by a shotgun? • Only by marks on the spent shell casing(s):

  29. Shotgun into ballistics gel

  30. B EXTERNAL BALLISTICS

  31. External ballistics is everything that happens after the bullet leaves the gun to just before the BULLET impacts its target

  32. GUN SHOT RESIDUE

  33. GUN SHOT RESIDUE (GSR) • CAN BE DETECTED EVEN AFTER WASHING CLOTHING / HANDS

  34. Gunshot Residues • Particles of unburned powder and traces of smoke are the residues of gunshots. • They can leave a trace on: • Shooter • hand, arm, face, hair, or clothing • Victim • Chemical testing often can detect residue even if removal is attempted. • The distance from the victim to the shooter can be determined by examination of the residue pattern on the victim.

  35. Wind shield Distance along path of bullet to window, 23.9” Path of bullet x y 60 feet Horizon Distance along horizon to window, 23.5” Trajectory

  36. Trajectory • 2 Reference points needed to determine trajectory • can be bullet holes in objects or victims. • Investigators can use lasers to trace a straight-line path to help determine the position of the shooter.

  37. http://www.glenbrook.k12.il.us/

  38. http://www.glenbrook.k12.il.us/

  39. External ballistics

  40. Point of initial intersection Point of impact Point of secondary intersection Maximum ordinate Point of aim

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