22 Types of firearm weapons Non-rifled: only longRifled: short and long
23 What happens?The holder presses the firing pin which in turn strikes the primer which ignites the powder and produces large amount of hot gas.Produces very high pressure that fires the bullet forcefully through the barrel leaving the muzzle, and onto the target.
24 Mechanism of injury:As the missile traverses the body it causes injury by:Basic contact of bullet and it’s fragments (if present) with the tissue, so larger bullets create bigger damage at the same velocity.Transferring some of its available kinetic energy to the tissue around it, so increasing velocity greatly increases damage.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.
25 SO… Mode of injury depends on the velocity of the missile -Slow velocity (<340 m/s) speed of sound in air or less-High velocity (1500 m/s) faster!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…
26 Smooth bore weapon (Shotgun): A gun with a smoothbore that shoots cartridges that contain "shot" or small metal pellets (of lead or steel) as the projectiles.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.
27 The rifle weapon:Rifles differ from shotguns in the length of the barrel and the presence of a butt stock.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.
38 AMMUNITION Head Stamps (Cont.) Civilian made with manufacturers symbol Military made with initials or codesYear of manufacturingMatch/nm = military match grade ammo+ = NATO+P or +P+ = High Pressure
39 AMMUNITION Bullet Powder Weights Grain = weight not granules 1 oz. = grains1 grain = gramsBullet and powder weights measured in grains
40 AMMUNITION Primer (Cont.) Non-corrosive/Non-mercuric Lead Styphnate Barium NitrateAntimony SulfideMost U.S. primers contain all three*Detection of these compounds provides bases for GSR
41 AMMUNITION Primers (Cont.) Rimfire Ammo No primer assembly Primer chemical is in rim
42 AMMUNITION Propellants Black Powder Charcoal is fuel SulfurPotassium NitrateCharcoal is fuelNitrate supplies oxygenSulfur creates density
43 AMMUNITION Propellants – Black Powder When powder burns Gas = 44%Residue= 56%Residue appears as dense white smoke
44 AMMUNITION Smokeless Powder 1884 Vieille – French Chemist NitrocelluloseUsed EtOH/EtherRolled into sheetsCut into flakesSingle base
45 AMMUNITION Smokeless Powder (Cont.) 1887 – Alfred Noble Nitrocellulose and NitroglycerineRolled and cut into flakesDouble base
46 AMMUNITION Ball Powder Winchester 1933 Nitrocellulose dissolved Formed into ballsDifferent diametersAppears uniform round, black spheres or ovalsReflective surfaceFlattened roundIrregularFlattened chipsWide variation between round and flat
63 Bullet Comparison Base markings Imprinted from propelled powder grains Most evident in bullets w/lead baseShorter barrel, deeper marksDifferent forms produce different marksSpherical=circular pitsDisk=circular imprintsBlack powder=peppered
74 Ballistics Movement through body Crushes/shred tissue in path Flinging, radially, surrounding tissueTemp. cavity several times (12) size of bulletLasts 5-10 msecPulsates, contractions and collapse+/- pressure sucks in bacteria/foreign materials
76 Ballistics Temporary/Permanent Cavity Max diameter of temp cavity is proportional to amount of kinetic energy lostOccurs at maximum yaw or fragmentsYaw continues until Cg is forward or approx 180 degrees rotationSize of cavity is determined by amount of K.E. lost by bulletSize of cavity is determined to a degree by cross section of round
78 Ballistics Temporary/Permanent Cavity (cont.) Compression, stretching, tearing of tissueHandguns-Damage to area hit by bullet, very little collateral damageRifles-Radial damage to nerves, tissue, vessels, organs not struck by bulletDamage related to density, elasticity and cohesiveness of tissueMuscle vs. Liver vs. Lung
80 Ballistics Energy loss along wound track Not uniform Changes and variations occur due to;Angle of yawChange in density of tissueChange in structural dimension of bullet (mushrooms)Fragmentation amplifies effect.223 marked yaw at 12cmMajor frag/tissue disruption at 15-25cm
82 Ballistics Critical velocity At or above 2625-2953 ft/sec (FMJ) At or above ft/sec (expanding ammo)Tissue damage more severeSupersonic flow = strong shockwavesShockwaves travel through bodyDamage is times largerDue to higher amount of K.E. loss
83 Ballistics Critical amount of K.E. loss Wounds are more severe Exceeds elastic limitsOrgan burstsProjectile does not have to be near organ
84 Ballistics Critical amount of K.E. loss-Head Special case Cranial cavity is a closed, rigid structure1% elasticityNo place for energy to disperseResults in bursting injuries (high velocity)
86 Ballistics Temporary cavity size Permanent Cavity size 10-12 times diameter of bulletHigh K.E. loss times bulletPermanent Cavity sizeHandgun=smaller than round diameterHigh velocity=size of bulletUnless Elastic limit of tissue is reached=large irregular tearing wound track.
87 Case StudyThis case involved a barroom shooting. The incident went something like this:
88 Case StudyGuy No.1- "Hey man, my quarters were up next!! I've got the next game on that pool table!!"
89 Case StudyGuy No. 2- "Man you’re crazy! I've had my quarters up there for over an hour!"
90 Case StudyGuy No. 1- "Oh yeah? Well not only are my quarters up next but your breath stinks too!!!"
100 Case StudyGuy No. 1 and Guy No. 2 run out of the bar get in a car and go home. They tell mom they have been to the movies, hide the gun under their bunk bed and go to sleep.
101 Case StudyMeanwhile back at the bar, a riot has ensued because the other guys with quarters on the table are really p off because the spent case has jammed the pool table. Order is finally restored when county police detectives clear the table.
102 Case StudyMy cold lifeless body is taken to the Medical Examiners Office for the 9 AM autopsy.
103 Case StudyGuy's No. 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.
104 Case StudyThe pistol, magazine, live ammunition, spent case, and bullet are later submitted to the lab for analysis.
105 Case StudyAlthough 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.
106 Case StudyFirst course of business is to examine the pistol, which is found to be in perfect working condition. 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.
107 Case StudyThe results of which are the match seen below.