6/21/2019 Gunshot Wounds • Tom Bennett, M.D. 1 6/21/2019 Ballistics • In general, ballistics is the study of the bullet in flight. We are more concerned with the effects once it strikes the target. • Internal ballistics = Physics of gunpowder ignition and propulsion of the projectile in the gun barrel. • Exterior ballistics: – Flight of the projectile. – Energy of bullet (K.E. = 1/2 mv²) • Wound ballistics: Physics of damage to the target tissue. We need to answer (at least): • What type of weapon (shotgun, handgun, etc.)? • What type of projectile within the weapon? (e.g., slug, birdshot, hollowpoint, jacketed, etc.) • What was the size of the projectile? • What was the angle with respect to the target surface? • Did the wound penetrate or perforate? • What was the range/distance from the end of the gunbarrel to the target surface? (i.e., touching or close or far…) • Are there any inconsistencies in scene, history, etc.? • Who fired the shot(s)? 2 6/21/2019 Weapon • Rifled: types –Handguns –Rifles • Airguns • Smooth bore: –Shotguns –Black powder Handgun – Rifle - Shotgun 3 6/21/2019 X-rays • Helpful to document injuries, etc. • Non-invasive, so do first to help direct course of autopsy. When the gun fires: • Each powder particle gives off 400-800 times its volume in gas when it burns. • Flame travels up to an inch or so from the end of the gun barrel. • Soot and primer residue travel about 6-12 inches from the barrel. • Gunpowder particles can predictably travel up to 30-36 inches from the end of the barrel. 4 6/21/2019 66m, told he had cancer. .380 semiautomatic • Entrance in center of upper eyelid, contact range. • 2 x 3” gaping exit hole in temple • Would you autopsy? 5 6/21/2019 • X-rays found the bullet at the back of the head. • Direction of bullet path was different than originally thought. Penetrated (not perforated), etc. • Left temple wound was blowout from gases blown into eye socket. What can you do to clean …? • Running water. • DON’T: • Hydrogen – Put sticks/probes peroxide (dilute). into the wound. – Scrub the wound • Shave the hair? with brush … • Scalpel blade to – Take them to the scrape the blood car wash to clean them up. away, etc. 6 6/21/2019 • Skin is the most difficult tissue in the human body for a projectile to pass Entrance through. wounds: • Size of the hole doesn’t equal diameter of projectile. • Abrasion collar minimal diameter approximates the diameter of the projectile. • Contact wounds have additional tearing of skin margins as well as possible muzzle impression. A = diameter Entrance of bullet, and wounds: the diameter of abrasion • Skin is so collar very elastic, that the hole at rest is smaller than the bullet A passing through. 7 6/21/2019 The size of the hole is NOT the size of the projectile. 8 6/21/2019 Multiple projectiles • Irregular entrance wounds, some penetrating. • What is this abrasion? • What does it tell you about range? Asymmetric entrance abrasion collars. 9 6/21/2019 Asymmetric entrance abrasion collars. • The wider abrasion collar is on the side the bullet comes from… • Contact range: – End of gunbarrel against the target surface. – The gases, flame, soot and gunpowder residue are Range of forced into the wound. Fire: • Close range: (intermediate range): – Some of the gases, soot, etc. deposited onto surfaces of target around the entry hole. • Distant/Indeterminate range: – Only the projectile(s) strike the target. 10 6/21/2019 Contact range wound-- • All of the gases, soot, gunpowder particles and projectile go into the Contact wound depths. • These gases (etc.) also wounds: cause injuries: – Larger gunpowder load more damage (lacerations, burns, abrasions,etc.) – The closer the skin surface to the underlying bone, the greater the chance for tearing, etc. 11 6/21/2019 Note: stellate laceration, soot on bone surfaces, frontal bone fractures, size of hole in bone, etc. 12 6/21/2019 •Muzzle imprint 13 6/21/2019 Muzzle impression 14 6/21/2019 • The loss of Kinetic Energy Tissue causes injury: – Initial K.E. – Terminal K.E. = Injury K.E. transmitted to tissue. • Tissue factors: – Density: Denser tissue (e.g., bone) has more drag and loss of K.E. – Elasticity: More elastic tissues (e.g., skin) will have less damage than solid tissues (e.g., liver). – Fluid-filled tissues: Tend to burst open upon impact due to diffuse transfer of energy (LaPlace’s Law). • A tumbling bullet increases surface area and drag. 15 6/21/2019 26m officer shot while seated in his patrol car. • Entrance wound left cheek. • Bullet wound up inside right mandible. Entrance • Size of projectile? • Range? 16 6/21/2019 Right cheek injuries. • No exit. • What are these irregular lines? 17 6/21/2019 Gun found in her hand, her finger on the trigger. • ? Suicide Cherry red? • CO • Nitrates • Oxygen/ air leak 18 6/21/2019 •27m, playing with .40 caliber handgun 19 6/21/2019 Soot forced into wound: -? Location -? MOD 20 6/21/2019 21 6/21/2019 22 6/21/2019 23 6/21/2019 CT Difference in range? -or difference in location 24 6/21/2019 Found dead in chair, with no gun in room • Range? • Angle? • Size of projectile? • Self- inflicted? 25 6/21/2019 • Two projectiles (penetrating, contact range). ? Suicide Perforation of vital organs • How soon would this render him unconscious or immobilized? 26 6/21/2019 27 6/21/2019 Loose contact range We need to take photos throughout 28 6/21/2019 • The gap allows for gases and other materials to escape from the margins. 29 6/21/2019 Close range • Includes wounds from contact range to where Close the last stippling or tattooing is seen. range • Measure the diameters of the stippling and soot, and use these for test firing studies • Consider saving gunpowder particles from the stippling on the skin surfaces to give clues for ammunition 30 6/21/2019 31 6/21/2019 Components travel different distances 32 6/21/2019 • Stippling is the more reliable of the range factors Shadowing? • Range? • Angle? 33 6/21/2019 •23m, .22 magnum, BAC.44%, freckles & stippling • Same weapon for the two wounds 34 6/21/2019 Loose-contact wound - suicide 35 6/21/2019 Entrance Wound • Inwardly beveled • Soot on bony margins 36 6/21/2019 37 6/21/2019 Intermediate target Range? 38 6/21/2019 Grazing gunshot wounds • Look for abrasion margin at end where the bullet entered, and tags of skin along the wound margins which point the direction the bullet came from… 39 6/21/2019 Shotgun • Brass base with plastic shell • Powder and piston • Wadding and Power piston – Diameter gives clues for gauge – 12 gauge is ¾ inch, 20 gauge is 5/8 inch. • Pellets or rifled slug – Not all pellets are “buckshot” Shotgun range 40 6/21/2019 SGW - Range estimation 41 6/21/2019 ? • Weapon? • Range? • Angle? 42 6/21/2019 • Shot in her apartment by her son’s friend. • What is the weapon? • What is the range? 43 6/21/2019 • Intermediate target 44 6/21/2019 45 6/21/2019 46 6/21/2019 47 6/21/2019 48 6/21/2019 • 17m, 74” tall • 12 gauge single-shot SGW to head. • Depressed over MIP that day. • Found supine on snow, with end of barrel held in left hand. • ? size of shot. 49 6/21/2019 Skin is the hardest tissue for a bullet to pass through. Exit wounds • Projectiles are tearing through the skin from underneath, after much velocity lost. • May be larger or smaller than entrance wound. • If abrasion is present on skin surface margins, think “shored” exit wound. • Skin is the hardest substance in the human body for a bullet to pass through. 50 6/21/2019 51 6/21/2019 Shored exit wound How bold can we be about reconstruction of the circumstances? 52 6/21/2019 Multiple small caliber GSW’s • ? defense wound in right hand 53 6/21/2019 Exit wounds – outward beveling 54 6/21/2019 55 6/21/2019 16m, 12 gauge-SGW chest 56 6/21/2019 57 6/21/2019 58 6/21/2019 59.