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CRIMINAL INVESTIGATIONS AMMUNITION/ BALLISTICS. AMMUNITION

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CRIMINAL INVESTIGATIONS AMMUNITION/ BALLISTICS
AMMUNITION Cartridge Structure –Cartridge Case –Primer –Head –Propellant –Bullet –Blanks- No Bullet
AMMUNITION Cartridge Cases –Made of Brass 30% Copper 30% Zinc –Aluminum –Brass, Plastic and Paper for shotguns
AMMUNITION Function of Cartridge –Expand and seal chamber –Increase Gas Pressure –Press the case up against barrel –Seals –Springs back to almost same size –Aids extraction
AMMUNITION Shapes –Straight –Bottle neck Permits more powder –Tapered Not in use
AMMUNITION Case Head Designs –Rimmed –Semi-rimmed –Rimless –Rebated –Belted
Rimmed Rimmed cartridges use the rim to hold the cartridge in the chamber of the firearm, with the rim serving to hold the cartridge at the proper depth in the chamber this function is called headspacing
Semi-Rimmed On a semi-rimmed case the rim projects slightly beyond the base of the case, though not as much as a rimmed cartridge.
Since there is no rim projecting past the edge of the case.
Functionally the same as a rimless case, the rebated rim provides some additional benefits when considered in conjunction with other cartridges..
The extractor groove is cut into the belt just as it is cut into the case head on a rimless case. The belt as as a rim on what is essentially a rimless case.
AMMUNITION Caliber Nomenclature –Rifled barrels Lands and grooves –Diameter of bore from land to land –Sometimes groove to groove diameter –Bullet diameter
AMMUNITION Types of Cartridge –R = Rimmed –SR = Semi-Rimmed –RB = Rebated –B = Belted –No letter for rimless
AMMUNITION Additional Terms –Magnum = Higher velocity than standard –Wildcat = Nonstandard, produced by small entity
AMMUNITION Head Stamps (Cont.) –Civilian made with manufacturers symbol –Military made with initials or codes Year of manufacturing Match/nm = military match grade ammo + = NATO +P or +P+ = High Pressure
System not consistent or accurate –.303 Savage =.308 bullet –.303 British =.312 bullet – and.308 both fire a.308 bullet –.06 refers to year made.
Caliber Designation –Confusing –Not accurate –.38 and.357 –Difference is length of case and grains of powder.
AMMUNITION Black Powder Cartridges –Designated by: Caliber Black powder charge Bullet weight –Examples: » »Some smokeless powder cartridges used this designation ».30-30
AMMUNITION Metric Designation –Bullet diameter –Case length –Type of cartridge
AMMUNITION Head Stamps –All cases have stamps on bases –Imprinted for Identification Purposes Letters Numbers Symbols Trade names
= grains –1 grain =.0648 grams –Bullet and powder weights measured in grains.
primers contain all three *Detection of these compounds provides bases for GSR.
AMMUNITION Primers (Cont.) –Rimfire Ammo No primer assembly Primer chemical is in rim
AMMUNITION Propellants –Black Powder Charcoal Sulfur Potassium Nitrate –Charcoal is fuel –Nitrate supplies oxygen –Sulfur creates density
AMMUNITION Propellants – Black Powder –When powder burns Gas = 44% Residue= 56% –Residue appears as dense white smoke
AMMUNITION Smokeless Powder –1884 Vieille – French Chemist –Nitrocellulose –Used EtOH/Ether –Rolled into sheets –Cut into flakes –Single base
AMMUNITION Smokeless Powder (Cont.) –1887 – Alfred Noble –Nitrocellulose and Nitroglycerine –Rolled and cut into flakes –Double base
AMMUNITION Ball Powder Winchester –1933 –Nitrocellulose dissolved –Formed into balls –Different diameters –Appears uniform round, black spheres or ovals –Reflective surface –Flattened round Irregular Flattened chips –Wide variation between round and flat
AMMUNITION Powder Grains –Disk –Flake –Cylinder –Uncoated (Greenish color) –Coated w/Graphite (shiny black)
Ammunition Powder (continued) –Powders burn at different rates –Gases and unburned grains are discharged upon firing –Grains can be found in clothing and skin
Rifle –Minnie ball (Capt.. Minnie, French Army) –Modern bullets Lead Metal-jacketed.
Ammunition Bullets –Various shapes Round Hollow point Semi-wadcutter Wadcutter
Ammo performance-Handguns CartridgeBullet gr.VelocityFt-lbs mm S&W ACP mag
Ammo performance-Rifles CartridgeBullet gr.VelocityFt-lbs x
Bullet Comparison Class characteristics –Number of lands and grooves –Diameter of lands and grooves –Width of lands and grooves –Depth of lands and grooves –Direction of rifling twist –Degree of twist
Bullet Comparison Individual Characteristics –Imperfections on lands/grooves –Score the bullets –Jacketed bullets, more pronounced –Are peculiar to each firearm
Characteristics –Rusted barrel –Jacketed/unjacketed –Velocity/pressure –Bullets vary from lot to lot.
Bullet Comparison Additional markings –Skid marks –Shaving Compositional Analysis –Fragments are recovered –SEM-EDX –Comparison between suspected guns bullets and recovered fragments
Bullet Comparison Base markings –Imprinted from propelled powder grains –Most evident in bullets w/lead base –Shorter barrel, deeper marks –Different forms produce different marks Spherical=circular pits Disk=circular imprints Black powder=peppered
Bullet Comparison Additional factors –Bullets fired in wrong caliber weapon –Decomposed bodies (Study after 66 days) Nylon clad-unaffected Aluminum-mildly affected Lead bullets, recovered from –Brain, chest cavity, abdomen-mild tarnish –Fat, muscle-severe oxidation-impaired match Copper alloy-severe degradation
Bullet Comparison Surface analysis of bullet –Non-organic material –Tissue analysis DNA typing
Cartridge Case Comparison Comparison MAY make ID possible –Type –Make –Model Test and evidence cartridges compared –Use same brand and lot Ammo consistency
Cartridge Case Comparison Markings=imprints or scratches –Magazine marks –Breech block marks –Firing pin marks –Size,shape, and location of; Extractor and ejector marks –Flute marks
Recall Kinetic Energy Equation –Greater the mass the greater the energy Double mass = double KE –Greater the speed the greater the energy Double speed = 4x increase KE Physics of Penetrating Trauma (continued)
–Different bullets of different weights traveling at different speeds cause Low Energy/Low Velocity –Knives and arrows Medium Energy/Medium Velocity Weapons –Handguns, shotguns, low-powered rifles – mps High Energy/High Velocity –Assault Rifles –600-1,000 mps (continued).
Physics of Penetrating Trauma Bullet spins as it travels down barrel –Rifling in barrel –Allows bullet to travel straight with slight yaw Bullet departs barrel, spinning with a slight wobble or yaw Weapon forced backward and absorbs energy –Recoil (continued)
Trajectory is curved due to gravity As bullet strikes object, it slows and energy is transferred to object. –Law of Conservation of Energy.
Energy Dissipation Drag: –wind resistance Cavitation: –formation of a partial vacuum and cavity within a semi-fluid medium Profile: –Size and shape of a projectile as it contacts a target –Larger the profile=greater energy exchange –Expansion and fragmentation results in damage Stability –Allows for straighter trajectory –Decreases after striking object results in tumbling
Aspects of Ballistics Velocity –Causes Trajectory Faster = straighter trajectory Slower = more curved due to gravity
Aspects of Ballistics Profile –Portion of bullet you see as it travels towards you Larger profile = greater energy exchange –Caliber Diameter of a bullet (ID of gun) –0.22 caliber = 0.22 inches –Bullets become unstable as they pass from one medium to another.
Aspects of Ballistics Expansion & Fragmentation –Results in increased profile –Mushrooming –Initial impact forces may result in fragmenting –Greater tissue damage
Aspects of Ballistics Secondary Impacts –Bullet striking other objects can cause yaw and tumble –Body Armor (Kevlar) Transmits energy throughout entire vest resulting in blunt trauma –Myocardial Contusion –Pulmonary Contusion –Rib Fractures Shape –Handgun Ammunition = Blunt = Tumble –Rifle Ammunition = Pointed = Piercing
Handguns –Small caliber, short barrel, medium-velocity –Effective at close range –Severity of injury based upon organs damaged Rifle –High-velocity, longer barrel, large caliber –Increased accuracy at far distances Assault Rifles –Large magazine, semi- or full-automatic –Similar injury to hunting rifles –Multiple wounds Specific Weapon Characteristics
Ballistics Ballistics=Study of motion of projectiles –Internal –External –Terminal Wound ballistics
Shotgun –Slug or pellets at medium velocity 00 (1/3 ) to #9 (pin head sized) Larger the load, the smaller the number of projectiles Deadly at close range Specific Weapon Characteristics
Damage Pathway Projectile Injury Process –Tip impacts tissue –Tissue pushed forward and to the side –Tissue collides with adjacent tissue Shock wave of pressure forward and lateral –Moves perpendicular to bullet path –Rapid compression, crushes and tears tissue –Cavity forms behind bullet pulling in debris with suction.
Damage Pathway Direct Injury –Damage done as the projectile strikes tissue Pressure Shock Wave –Human tissue is semi-fluid –Solid and dense organs are damaged greatly Temporary Cavity –Due to cavitation Permanent Cavity –Due to seriously damaged tissue Zone of Injury –Area that extends beyond the area of permanent injury
Density of tissue affects the efficiency of energy transmission –Resiliency Strength and elasticity of an object Connective Tissue –Absorbs energy and limits tissue damage Organs –Solid Organs Dense and low resilience –Hollow Organs Fluid filled: transmit energy = increased damage Air filled: absorbs energy = less damage Specific Tissue & Organ Injuries
Lungs –Air in lung absorbs energy –Parenchyma is compressed and rebounds –Pneumothorax or hemothorax can result Bone –Resists displacement until it shatters –Alters projectile path Specific Tissue & Organ Injuries
General Body Regions Extremities –Injury limited to resiliency of tissue –60-80% of injuries with <10% mortality Abdomen (Includes Pelvis) –Highly susceptible to injury and hemorrhage –Bowel perforation: hrs peritoneal irritation Thorax –Rib impact results in explosive energy –Heart & great vessels have extensive damage due to lack of fluid compression –Any large chest wound compromises breathing
lost by bullet –Size of cavity is determined to a degree by cross section of round.
General Body Regions Neck –Damages Trachea and Blood Vessels –Neurological problems –Sucking neck wound Head –Cavitational energy trapped inside skull –Serious bleeding and lethal
Energy loss along wound track –Not uniform –Changes and variations occur due to; Angle of yaw Change in density of tissue Change in structural dimension of bullet (mushrooms) –Fragmentation amplifies effect.223 marked yaw at 12cm Major frag/tissue disruption at 15-25cm
loss –Wounds are more severe –Exceeds elastic limits –Organ bursts –Projectile does not have to be near organ.
loss-Head –Special case –Cranial cavity is a closed, rigid structure –1% elasticity –No place for energy to disperse –Results in bursting injuries (high velocity).
Ballistics Temporary cavity structure –FMJ –Hunting rifle round –Shotgun pellet
loss times bullet Permanent Cavity size Handgun=smaller than round diameter High velocity=size of bullet Unless Elastic limit of tissue is reached=large irregular tearing wound track..
Case Study This case involved a barroom shooting. The incident went something like this:
I ve got the next game on that pool table!! .
Case Study Guy No. 2- Man you’re crazy! I ve had my quarters up there for over an hour!
Well not only are my quarters up next but your breath stinks too!!! .
Case Study Guy No. 2- You son-of-a- XXXXX!!!!! I m gunna kill you!!!
Case Study Me- Now guys, calm down it s only a pool game; it s only a quarter.
Case Study Guy No.1 pulls out the Llama 45 auto below and points it at Guy No. 2.
2, missing him and hitting me right between the eye s with this 45 AUTO, 230 grain full-metal-jacketed bullet..
Case Study At the same time the pistol ejects the 45 AUTO cartridge case below into the corner pocket of the pool table.
They tell mom they have been to the movies, hide the gun under their bunk bed and go to sleep..
Order is finally restored when county police detectives clear the table..
Case Study My cold lifeless body is taken to the Medical Examiners Office for the 9 AM autopsy.
1 and 2 are later roused from bed by Detectives and the pistol, it s magazine, and four 45 AUTO cartridges are recovered from under the bed..
Case Study The pistol, magazine, live ammunition, spent case, and bullet are later submitted to the lab for analysis.
Case Study Although my ex-coworker is all but overcome with grief, he manages to set aside his personal ties to the case and conducts the required analysis in a totally professional and unbiased fashion.
The pistol is test fired in the water tank and standards from the pistol are compared to the spent case from the pool table and bullet from my head..
Case Study The results of which are the match seen below.
Case Study Breech Marks: Standard from pistol (left) compared to the spent case from the bar (right).
Case Study Bullet land impression comparison: Standard (left) compared to my bullet (right).
Case Study By the way, Guy 1 walks when his brother testifies that I started the fight by stealing his brother s hot wings.
Case Study They really do have the best hot wings in town!!!
5.56 Centerfire vs. Rimfire
Bore: the inside of the barrel, either:  Smooth bore: Shotguns.  Not smooth bore: rifles, pistols..
Primer: volatile substance that ignites when struck to detonate the powder in a cartridge..
Types of firearm weapons Non-rifled: only long Rifled: short and long
Produces very high pressure that fires the bullet forcefully through the barrel leaving the muzzle, and onto the target. What happens .
Basic contact of bullet and it’s fragments with the tissue, so larger bullets create bigger damage at the same velocity. 2. Transferring some of its available kinetic energy to the tissue around it, so increasing velocity greatly increases damage. 3. It also causes cavitations in the tissue it passes as it accelerates molecules → makes them move centrifugally away from the axis of the bullet.  Bullets do not typically follow a straight line to the target. Rotational forces are in effect that keep the bullet off a straight axis of flight..
High velocity missile causes a shockwave around it’s track → severe disruption → ↑ tissue pressure and more damage. So a 10mm wide bullet may cause a 15mm wide track of damage… SO….
Ammunition: A shotgun shell(cartridge) may contain one large projectile (called a slug), a few pellets of large shot, or many tiny pellets. Cartridge made of a cylinder fitted into a metal base contains charge of propellant, wads, and shots. Range is the most important factor, and can be estimated in over half of cases… Close range wounds are severe, but at even relatively short distances, wounding may be minimal..
They fire one projectile at a time through a thicker barrel that has spiral grooves on its inner surface → rotational movement. They are much more accurate and shoot more powerful cartridges than handguns. Ammunition: metal cylinder loaded with explosive propellant and bullet..
Rifle bullet/pistol bullet
Ballistics Forces –K.E.=1/2mv 2 –Velocity place larger role in force –Doubling mass, doubles force –Doubling velocity quadruples force –Energy transfer/loss
upon impact –Angle of yaw upon impact –Caliber, construction, shape –Density, strength, elasticity of tissue.
Ballistics-Structural Mechanics Elasticity (Stretching) Shearing Compression Cohesiveness Tensile strength Density
cavity several times (12) size of bullet –Lasts 5-10 msec –Pulsates, contractions and collapse –+/- pressure sucks in bacteria/foreign materials.