BALLISTICS

1. BALLISTICS Handguns&Rifles

2. Introduction • Structural variations and irregularities caused by scratches, nicks, breaks, and wear may permit the criminalist to relate: • A bullet to a gun • A scratch or abrasion mark to a single tool • A tire track to a particular automobile • Individualization, a goal of in all areas of criminalistics, frequently becomes an attainable reality in firearm and tool mark examination.

3. HANDGUNS

4. Firearm Investigation • Firearms produce characteristics on the ammunition to help identify the type of weapon that was used to fire it. • If only fired ammunition is found, it may be possible to determine the model of firearm that was involved

5. Aspects of Firearm Investigation • Identifying the type of ammunition from used bullets, cartridge cases, marks and residue • Linking crimes when the same weapon was used • Estimating the distance the weapon was from the target when it was fired

6. Aspects of Firearm Investigation • Determining the location of the shooter from the direction of travel of bullets and location of spent cartridge shells • Restoring serial numbers that have been scratched off in effort to disguise a weapon

7. Evidence Typical evidence left on scene may include • Recovered weapons • Fired and unfired cartridges • Silencers • Magazines

8. Firearm Evidence Collection • Firearms are collected by holding the weapon by the edge of the trigger guard or by the checkered portions of the grip. • Before the weapon is sent to the laboratory, all precautions must be taken to prevent accidental discharge of a loaded weapon. • In most cases, it will be necessary to unload the weapon. • When a revolver is recovered, the chambers, their positions, and corresponding cartridges must be recorded. • Firearm evidence must be marked for identification (usually a tag on the trigger guard) and a chain of custody must be established.

9. Firearm Evidence Collection • Bullets recovered at the crime scene are scribed with the investigator’s initials, either on the base or the nose of the bullet. • The obliteration of striation markings that may be present on the bullet must be scrupulously avoided. • The investigator must protect the bullet by wrapping it in tissue paper before placing it in a pillbox or an envelope for shipment to the crime laboratory. • Fired casings must be identified by the investigator’s initials placed near the outside or inside mouth of the shell. • Discharged shotgun shells are initialed on the paper or plastic tube remaining on the shell or on the metal nearest the mouth of the shell.

10. The Modern Cartridge A modern cartridge is made up of five components: • The bullet itself, which serves as the projectile • The casing which holds all parts together • The explosive, for example gunpowder or which serves as a propellant • The rim, at the base of the cartridge • The primer which ignites the propellant.

11. Types of Bullets • Full Metal Jacket • Round Nose • Hollow Point • Wadcutter

12. FMJ vs. Hollow-Point • Ball ammunition - designed to keep it's shape and form upon impact. • Hollow-point/defensive ammunition is meant to deform & expand upon hitting a solid obstacle. • Self-defense rounds tend to leave their energy in the object hit • Ball ammunition will continue through the object and thus tend to damage less butrisk possible over penetration.

13. Ball Ammunition • Projectiles will keep their shape and mass when hitting an object and continue on • Will not cause a large temporary or permanent wound cavity.

14. Hollow Point Ammunition • Specifically designed to expand when it strikes solid material. The hollow-point projectiles have a hollow indentation at the front of the projectile which is designed to mushroom open upon contact. • Energy contained in the round is expanded very quickly in a small distance, and the temporary wound cavity as well as the permanent wound volume is much larger than that of practice rounds.

15. Hollow Point Ammo

16. Handguns • Single-shot pistols • Fire only one round at a time • Revolvers • Feature several firing chambers within a revolving cylinder • Include swing-outrevolvers, break-top revolvers, and solid frame revolvers • Semi-automatic pistols • Feature a removable magazine • Fire one shot per trigger pull

17. Revolver • Handgun that has a cylinder with holes that contain cartridges. The cylinder revolves to bring the cartridge into position to be fired.

18. Revolver • Less expensive • Simple design • More reliable and accurate than semi-autos • Able to fire the most powerful and largest cartridges

19. Revolver • Cylinder contains on average 5 to 7 holes for the cartridges and can be swung out for easy reloading. No cartridge cases will be found at a crime scene unless the suspect stopped to reload or picked up the empty cases

20. Revolver • There is a gap between the cylinder and barrel to allow the cylinder to turn freely, but this allows gases to escape, which at close range may deposit gunshot residue on surrounding areas and allow the CSI to reconstruct the scene.

21. Semi Automatic • Forces generated by the burning gunpowder force the slide backwards against a spring. Cartridges are loaded into a spring-loaded magazine and inserted into the grip of a weapon. As the slide is forced back by the firing of the weapon, the empty cartridge case is extracted from the chamber and ejected from the weapon, and a new cartridge is stripped off the magazine and fed into the chamber as the slide moves forward.

22. Semi Automatic • The advantage of semi-auto handguns is the use of recoil generated by the fired cartridge to eject the empty cartridge cases, load the next cartridge, and cock the hammer. • Able to carry numerous rounds; some up to 20

23. Semi Automatic Casings • Empty cartridge cases may land from 2-20ft. from the fired gun. • Ejected cases may be hard to find as they may roll into a hiding place such as grass or under objects. Ejected cases will virtually always be left behind at the scene

24. Firearm Barrel • The barrel of a firearm is a metal tube made by drilling out a steel rod. The barrel is typically rifled

25. Gun Barrel Markings • The inner surface of the barrel of a gun leaves its markings on a bullet passing through it. • These markings are peculiar to each gun. • The gun barrel is produced from a solid bar of steel that has been hollowed out by drilling. • The microscopic drill marks left on the barrel’s inner surface are randomly irregular and serve to impart a uniqueness to each barrel.

26. Gun Barrel Markings • The manufacture of a barrel also requires impressing its inner surface with spiral grooves, a step known as rifling. • The surfaces of the original bore remaining between the grooves are called lands. • The grooves serve to guide a fired bullet through the barrel, imparting a rapid spin to insure accuracy.

27. Gun Barrel Markings • The diameter of the gun barrel, measured between opposite lands, is known as caliber. • Once a manufacturer chooses a rifling process, the class characteristics of the weapon’s barrel will remain consistent, each will have the same number of lands and grooves, with the same approximate width and direction of twist.

28. Striations • Striations, which are fine lines found in the interior of the barrel, are impressed into the metal as the negatives of minute imperfections found on the rifling cutter’s surface, or they are produced by minute chips of steel pushed against the barrel’s inner surface by a moving broach cutter. • These striations form the individual characteristics of the barrel. • It is the inner surface of the barrel of a gun that leaves its striation markings on a bullet passing through it.

29. Bullet Examination • No two rifled barrels, even those manufactured in succession, will have identical striation markings. • The number of lands and grooves and their direction of twist are obvious points of comparison during the initial stages of an examination between an evidence bullet and a test-fired bullet. • Any differences in these class characteristics immediately serve to eliminate the possibility that both bullets traveled through the same barrel.

30. The Comparison Microscope • The comparison microscope serves as the single most important tool to a firearms examiner. • Two bullets can be observed and compared simultaneously within the same field of view. • Not only must the lands and grooves of the test and evidence bullet have identical widths, but the longitudinal striations on each must coincide.

31. The Comparison Microscope Goddard – Inventor of the Comparison Microscope

32. The Comparison Microscope • Consists of two microscopes connected to an optical bridge that results in a split view window. • A device used to analyze side-by-side specimens is called a comparison microscope. • Used in forensic sciences to be able to compare microscope patterns and identify or deny their common origin. Handguns predominated as the firearm of choices in shooting-related crimes, especially in the United States of America

33. Land and Groove Impressions • Rifling refers to the groves cut inside the surface of the barrel. • The uncut metal is known as the land. • As the bullet travels along the barrel, it will scrape against the rifling as it heads out the muzzle. • The bullet will now show the marks of the groves in the rifled barrel

34. Land and Groove

35. Land and Groove • Each barrel has its own unique set of imperfections in the rifling • Close examination of a bullet for these marks allows it to be matched to a particular weapon that fired it

36. Distinctive Marks • When the weapon is fired, the firing pin strikes the primer of the cartridge resulting in contact marks and indentations • When the cartridge is ejected from the gun, this may leave gouged impressions on the rim and head of the case

38. RIFLES and SHOTGUNS

39. Long Guns Long guns may be single-shot, repeating, semi-automatic, or automatic. • Shotguns • Shell ammunition contains numerous ball-shaped projectiles, called shot • Narrowing of the smooth barrel, called the choke of the shotgun, can concentrate shot when fired • Rifles • Feature a barrel with lands and grooves • Bullet ammunition is impressed with lands and grooves during firing

40. Pump Action Rifle Shotgun With a pump action weapon a suspect could easily clean up spent cartridges or shells.

41. Semi-Automatic Shotgun Rifle This weapon would spray spent cartridges all over the place, investigators would most likely find spent cartridges.

42. Bolt-Action Rifle Shoatgun This would enable a suspect to take the cartridge with them.

43. Other Sideby side Over/Under Suspect can take spent shells.

44. Muzzleloader Most commonly a rifle, but they do make shotguns. If this were used in a crime it would leave a lot of evidence do the burning of black powder. You may find a sabot and a primer but no cartridge.

45. Automatic • This is illegal to own in the United States • Military and law enforcement agencies use them. • Criminals do get a hold of them and they usually have the high capacity magazines to go with them. • Leaves spent cartridges all over the place. • This M-4 can be equipped with a 90 round magazine. This magazine is legal to purchase in most states.

46. Shotguns • Unlike rifled firearms, a shotgun has a smooth barrel. • Shotguns generally fire small lead balls or pellets that are not impressed with any characteristic markings that can be related back to the weapon. • The diameter of the shotgun barrel is expressed by the term gauge. • The higher the gauge number, the smaller the barrel’s diameter.

47. ShotgunShells 12ga 2 3/4 12ga 2 3/4 12ga 3 12ga 3 12ga 3 1/2 These come in 10,12,16,20,28 gauge and .410 caliper. Smaller the number bigger the shell. They are filled with different types of shot for different purposes. All these types of shot leave a different mark.

48. Rifle Cartridges Rifles fire a bullet. It rides down the barrel and the rifling in the barrel forces it to spin making it stable in flight. The rifling also leaves a mark on the bullet “Lands and Groves”. Investigators can use these marks to find out what kind of gun the bullet came from.

49. Rifling is what makes the Lands and Grooves in a bullet

50. Caliber 45-70 Gov’t., 223 Remington 30-06 Springfield, 458 Winch. Caliber is 100ths of an inch, for example 1 inch is 100 caliber. Rifle cartridges come in hundreds of sizes. Each gun is made for a specific cartridge. If investigators find a bullet at a crime scene they can find out what caliber it is and what kind of lands and grooves it has. Then they might be able to find out what kind of gun fired it.