Presentation on theme: "Chapter 15, Firearms. From left 50 BMG, 300 Win Mag,.308 Winchester, 7.62x39mm, 5.56x45mm NATO,.22LR.22LR."— Presentation transcript:
Chapter 15, Firearms
From left 50 BMG, 300 Win Mag,.308 Winchester, 7.62x39mm, 5.56x45mm NATO,.22LR.22LR
Firearms: DC Sniper case Discussion What Forensic evidence can be obtained from firearms? October 2-October acts of violence –10 killed –3 injured –1 assault on a Michaels craft store window
Firearms: DC Sniper case Forensic evidence obtained October 2-October acts of violence DNA, (Multiple Sources) Casings Projectile Fragments Projectiles Later used to confirm –semiautomatic.223-caliber firearm
Firearms: DC Sniper case John Allen Muhammad, 41 Born John Allen Williams Found guilty, received the death penalty his execution by lethal injection on November 10, John Lee Malco, 17 Life without parole
Firearms: DC Sniper case John Allen Muhammad, 41 Mildred Muhammad, the sniper's second ex- wife and the mother of three of his children, told CNN on Monday that she last saw him in 2001 at a custody hearing and had not sought to visit him in prison. "I had emotionally detached from John when I asked him for a divorce," she told CNN. "And my emotions were severed when he said that you have become my enemy and as my enemy, I will kill you. She has asserted that she was her ex- husband's target, and she blamed the first Gulf War for changing his personality.
Firearms Demo The rifle is chambered for the.577 Tyrannosaurus Rex. According to reloading data, the 13.6 pound rifle At a velocity approaching 2600 fps for a muzzle energy of over foot-pounds. This energy is comparable to that of the US military's.50 BMG cartridge frequently used as a heavy machinegun and anti-material rifle.
Gun Safety Rules 1. ALWAYS keep the gun pointed in a safe direction. 2. ALWAYS keep your finger off the trigger until ready to shoot. 3. A LWAYS keep the gun unloaded until ready to use.
Chapter 15, Firearms
What is Firearm Identification? Firearms Chapter 15 Outline What is Firearm Identification? Three basic Rules of Firerarm Safety What is Ballistics Bullet Comparisons, Types Caliber Anatomy of a bullet Cartridge Cases Firearms Types Anatomy Automated Firearms Search System National Integrated Ballistic Information Network (NIBIN) Gunpowder residue Primer residue Serial Number Restoration
What is Ballistics? Ballistics: is the study of bullets and firearms Firearm: a weapon capable of firing a projectile.
What evidence does Firearms Identification provide?.
What evidence does Firearms Identification provide? Comparison of bullets Identification of varying weapon types Restoration of obliterated serial numbers Detection and characterization of gunpowder residues (garments and wounds) Estimation of muzzle to target distance and angle from target Powder residues of hands
Anantomy of a Bullet
38 Caliber Bullets Casings 44 Caliber
Anantomy of a Bullet
Parts of a Bullet Animation Different amounts of powder affects the strength of the shot
Types of Bullets 1. Frangible Bullets 2. Non-Expanding Bullets -Full Metal Jacket 3. Expanding Bullets
Frangibles Frangible bullets break up into very small pieces upon impact with the target or the background. The penetration of this type of bullet is limited and the inflicted damage is typically near the surface of the target. They are the safest type of bullet to use in semi-populated areas, as the risk of ricochet is minimized.
Non-Expanding Bullets Non-expanding (FMJ) bullets typically retain their general shape as the bullet penetrates and passes through target. The penetration of this type of bullet is usually much greater than frangible or expanding bullets because the frontal area of a non- expanding bullet does not increase as it penetrates. Since the wound channel is typically much narrower than that of an expanding bullet, the damage caused by a non-expanding bullet is usually much less, and quick kills on deer size game are rare. For this reason non-expanding FMJ bullets are illegal for big game hunting almost everywhere in North America. In round nose form they are favored by some African hunters for use on the largest and toughest game, principally on elephant and rhino, where very deep penetration against heavy hide and bone is required.
Full metal jacket (or FMJ) is a bullet consisting soft core (usually made of lead) encased in a shell of harder metal, such as gilding metal, cupronickel or less commonly a steel alloy. This shell can extend around all of the bullet, or often just the front and sides with the rear left as exposed lead. (A bullet that is completely enclosed by the shell is termed a total metal jacket round.) The jacket allows for higher muzzle velocities than bare lead without depositing significant amounts of metal in the bore. It also prevents damage to bores from steel or armor- piercing core materials.
Expanding Bullets Expanding or "controlled expansion" bullets are designed to deform or "mushroom" as the bullet penetrates and passes through the target. Expanding bullets are the most complex and difficult type of bullet to design, and also the most useful and numerous type of bullet. Almost all big game hunting bullets are of the expanding type. The penetration of an expanding bullet may be measured in inches or feet, depending (among other things) on the bullet's design, the bullet's sectional density, the expansion medium the bullet hits, and how fast it is traveling when it hits the expansion medium. Expanding bullets are normally used to humanely kill animals greater than approximately 30 pounds in weight by creating significant tissue damage as the bullet passes through the animal. Expanding bullets are generally constructed to (ideally) mushroom to approximately twice their initial diameter as the bullet passes through soft to firm tissue, such as skin, fat, muscle, small bones, and internal organs. The objective is to cause catastrophic damage to vital organs, especially the heart and lungs, so that the animal dies as quickly as possible.
Caliber vs. Millimeter bore
Understanding Caliber Caliber is simply a unit of measurement of the diameter of the bullet using inches..45 caliber means.45 inches wide. On the other hand, mm is the metric system measurement. 9mm means 9 millimeters wide. To convert use 1 inch = 25mm. ".38 special" measure " and a 9mm measures.355" instead of.354".
Always match the data
38 Caliber and 44 Caliber
Types of firearms Handguns Black Powder Revolvers Semi/Automatic Rifles Black Powder Bolt Action Semi Automatic Fully Automatic Shotguns
Shotguns Gauge One of the earliest ways to designate the size of the bore of a gun was to figure how many bullets for it could be made from a pound of lead. Since at that time all bullets were roundballs of lead, this made a good standard. In time this designation of 'balls to the pound' became synonymous with gauge, so that what our forefathers called '28 to the pound', we now call '28 gauge'. The British commonly used the term 'bore' for 'gauge', so their '28 bore' is the same as '28 gauge' or '28 balls to the pound'. Knowing that there are 7000 grains in a pound, we can simply divide 7000 by 28 and see that 28 gauge balls weigh 250 grains each. If we measure one of those balls, we see that it is.550 inches in diameter. In modern usage that is the same as '.55 caliber'. The same relationship holds true for any size bore, of course.
Shotguns vs Rifles The major difference between the two is Barrel rifling. Rifles are, Shotguns are NOT Grooves purposely scribed into the barrel of the rifle to induce spin which increases accuracy
The Barrel rifling
Rifling Terminology: Bore : the interior of the firearm barrel Barrel drilling leaves behind irregular marks Rifling: spiral grooves that are formed in the boring of a barrel, designed to produce projectile spin Produces – grooves – lands
Markings on Casing Lands and Grooves Firing Pin Ejector
Firearm Identification Bullet Comparisons Lands - In a rifled barrel, the raised spiral ribs left between the grooves in the bore. This is the part of the barrel that actually engraves the bullet, imparts the spin to the bullet, and ultimately stabilizes the bullet. Rate Of Twist - In a barrel, the length over which the rifling grooves make one complete twist ( i.e. the length of the bore used to turn the bullet one full revolution ) e.g. 1:10 or one revolution in 10 inches. Differs from caliber to caliber. Bullet weight must be appropriate to the rate of twist or bullets will not stabilize in flight. The heavier the bullet, thus the longer, the faster the twist rate must be.
Lands and Grooves
Firearms Identification, Comparison of bullets Inner striations of gun barrel leave impressions on bullet These striations are individual characteristics The widths of the lands and grooves on a bullet provide a further class characteristic that can be used as a preliminary means to determine if the submitted bullet could have been fired from the submitted firearm.
Comparison scope of lands and grooves match up.
Firearms Identification, Comparison of bullets There are three basic machining processes Rifling can be cut into the inner surface of a barrel using a broach, the rifling can be formed using a hardened steel button, the rifling will be formed through a process called hammer forging. A newer method of rifling barrels, called Electrochemical Rifling, does not involve the normal machining processes of the other techniques.
Firearm Identification Bullet Comparisons Rifling will ensure that the bullet flies true with a point-first attitude.. Methods of manufacturing are Button rifling, Cut rifling Hammer forging.
Firearm identification The first step in a firearm identification is to look at what are called class characteristics. These are characteristics common to a particular group or family of items. In the case of a firearm these would be the caliber –The caliber of the firearms refers to the size of the bullet that is fired. Obviously a bullet that is 0.30" in diameter could not be discharged from a firearm that has an inside barrel diameter of 0.15". The rifling pattern on rifling pattern of the barrel. –the inside of a barrel is often unique to a specific firearm manufacturer. This pattern is the spiral staircase pattern that can be seen when looking down the barrel of a firearm.
Bullet Comparison Water TankComparison Microscope
Bullet Trajectory Using Hole A Mr. Vickers was found dead on the floor of his apartment. It was determined that he was shot on the floor after a struggle from eight feet away. What was the arm height of the assailant. Mr. Vickers was found dead on the floor of his apartment. It was determined that he was shot on the floor after a struggle from eight feet away. What was the arm height of the assailant.
Bullet Trajectory Angle of elevation Angle of elevation
Bullet Trajectory A. 2degrees shooter? A. 2degrees shooter? B. 25, degrees B. 25, degrees C. -45 degrees C. -45 degrees