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Firearm Wounds

Firearm Wounds. By Dr. Arif Rasheed Malik Associate Professor & Head Department of Forensic Medicine & Toxicology, SIMS, Lahore. Firearm. “ An instrument or device with which it is possible to propel a projectile by means of the expansive force of the gases generated by the combustion

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Firearm Wounds

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  1. Firearm Wounds By Dr. Arif Rasheed Malik Associate Professor & Head Department of Forensic Medicine & Toxicology, SIMS, Lahore

  2. Firearm “ An instrument or device with which it is possible to propel a projectile by means of the expansive force of the gases generated by the combustion of an explosive substance “ Firearm wounds “ Firearm wounding is a special form of trauma producing a breech through the body of a person by a bullet or shot charge “ Principles & Practice of Forensic Medicineby Nasib R. Awan

  3. Ballistics “ Knowledge of physical forces acting on the projectile & missile “ by Nasib R. Awan Interior Ballistics Exterior Ballistics Terminal / Wound Ballistics

  4. WOUND BALLISTICS Definitions: Ballistics is the science of the motion of projectiles. Interior ballisticsis the study of projectiles in weapons. External ballistics is the study of projectiles in the air. Terminal ballistics is the study of projectile penetration of solids. Wound ballistics is the study of projectile penetration of tissues.

  5. Ballistics T H E O R E T I C A L P R A C T I C A L Interior ballistics Wound ballistics Exterior ballistics Clear Concept

  6. INTERIOR BALLISTICS • Knowledge of the forces responsible for propulsion of projectile within the bore of the barrel till the end of the projectile.

  7. Understanding pre-requires knowledge of:- 1- Missile design & cycle of fire. 2- Ammunition design. Missile design & cycle of fire Missile design:- a- Portion containing mechanical device (not important). b- Barrel for jetting of the projectile (Important because it has relation to WOUND BALLISTICS).

  8. Firearm Design Grip Action Barrel Barrel Grip or But Stock Action

  9. Classification of Firearms Classified on the basis of Barrel • Barrel • Steel tube for jetting of the projectile. Two ends --- Breach & Muzzle end • Bore • Internal diameter of the barrel. May be SMOOTH or RIFLED

  10. Classification of Firearms • Smooth Bored • Choked • Non choked • Rifled • Short Barrel • Long Barrel Rifling Barrel

  11. Choking of Smooth bore Firearm 18.80 mm 18.40 mm Cylindrical portion

  12. TYPES OF CHOKING OF BARREL OF SHOT GUN

  13. Cycle of fire:- Three stages:- • i- Cartridge feeding and chambering. • ii- Striking of fire pin • iii- Extraction of fire cartridge.

  14. Ammunition DesignProjectile consists of:- • Cartridge Case • Primer • Powder charge (Black or Smokeless) • Plastic Wad • Shot charge (Bullet or Lead shots) C A R T R I D G E B U L L E T

  15. CARTRIDGE CASE Function: expands and seals chamber against rearward escape of gases. Composition: usually brass (70% copper, 30% zinc); also plastic and paper in shotgun shell tubes. Shape: (a) straight ("always" pistol ammunition) (b) bottleneck ("always" rifle ammunition) (c) tapered ("obsolete"). Extractor flange: configuration at base; rimmed, semi-rimmed, rimless ,belted, rebated. Headstamp: manufacturers identifiction imprinted or embossed on cartridge case.

  16. Cartridge Case Cartridge cases (outer covering of the cartridge) are made up of Cardboard & plastic. Bullet cases are made of brass (70% copper and 30% zinc). A few have a nickel coating. Primer cases are of similar composition (Cu-Zn). Bullet cores are most often lead and antimony, with a very few having a ferrous alloy core. Bullet jackets are usually brass (90% copper with 10% zinc), but some are a ferrous alloy and some are aluminum. Some bullet coatings may also contain nickel (Ravreby, 1982)

  17. FUNCTIONS OF CARTRIDGE CASE • CONTAINS AND KEEPS THE INNER CONTENTS IN POSITION • PREVENTS THE BACK ESCAPE OF GASES • PROTECTION TO THE CONTENTS TYPES OF CARTRIDGE CASES Rimmed, Semi rimmed, Rimless, Rebated, Belted CASAELESS CARTRIDGE

  18. Rimmed Case : A rimmed case is distinguished by a rim that extends outward from the head of the case, to a diameter noticeably larger than the case body. Semi-Rimmed : Semi-rimmed design is a rim only slightly larger than the case body itself. Rimless : Despite the “rimless” designation, the case does indeed have a rim to facilitate extraction. In this design, however, the rim does not extend beyond the case body. Rather, the rim diameter is approximately equal to the diameter of the case body itself just ahead of the extractor groove.

  19. Belted : The defining characteristic of these cartridges is a small band, or belt, around the head of the case, just ahead of the extractor groove. In use, the belt acts in exactly the same manner as a rim. Originally, this was an absolute necessity, owing to the steeply sloping shoulders of many of the first belted cases. Rebated : the rebated case is characterized by a rim that is noticeably smaller in diameter than the case body. The intent of this design is normally to offer increased case capacity without altering or enlarging an existing bolt face.

  20. Primer The major primer elements are Lead styphnate(Pb), Barium nitrate (Ba), or Antimony sulphide(Sb). Usually, all three are present. Less common elements include Aluminum (Al), Sulfur (S), Tin (Sn), Calcium (Ca), Potassium (K), Chlorine (Cl), or Silicon (Si). Primer elements may be easier to detect in residues because they do not get as hot as the powder, and compounds (not just elements) may be detectable. (Tassa et al, 1982b)

  21. Function: explodes on compression igniting the propellant. Location: (a) centrefire. Centrally placed primer assembly comprising primer cup (struck by firing pin), primer, anvil with flash holes. Boxer design (USA) or Berdan design (Europe). (b) rimfire. No primer assembly. Primer spun into rim of cartridge case (rim struck by firing pin) and in contact with propellant.

  22. Various types of Ammunition

  23. Powder Charge • Modern gunpowder, or "smokeless" powder, can contain up to 23 organic compounds (FBI study)Nitrocelluloseis virtually always present, along with other compounds containing nitrate or nitrogen. • One of these compounds, diphenylamine(used as a stabilizer in the powder), can be detected using reagents containing sulfuric acid.(Maloney et al, 1982). • Modern gun powders are also described as "single-base" when the basic ingredient is nitrocellulose and as "double-base" when there is additionally 1 to 40% nitroglycerine added. If nitroguanidine it is “Triple – base”. • Hardy and Chera (1979) describe a method to differentiate them using a mass spectrometer .

  24. BLACK GUN POWDER

  25. PROPELLANT Function: burns to produce large volumes of gases under pressure. Shape: sheets of smokeless powder cut into disc, flake or cylinder shapes. Alternatively produced as ball and flattened ball smokeless powder (Winchester) which may be coated with silver-black graphite.

  26. Figures: Lead bullets: (a) round nose; (b) semi-wadcutter; (c) hollow-point; (d) wadcutter.

  27. Chain of Events Gases produced: Carbon dioxide, Carbon monoxide Nitrogen, Sulphurated hydrogen

  28. CHAMBER PRESSURE:- i- Revolver:- 4 tons ii- Pistol:- 6 tons iii- Rifle:- 20 tons Bullet:- Forward & rotational motion. Shot charge:- Forward movement.

  29. Exterior Ballistics “ Knowledge of forces acting on the shot while it leaves the barrel till it reaches the target “ Interactions of forces:- 1- Forces originating from the bullet motion a- Velocity:- i- Forward (Rate of motion (speed) and Direction ii- Rotational :- It varies (length of the barrel) b- Velocity of bullet at the muzzle end for various firearms:- i- Revolver:- 600 – 900ft/sec ii- Pistol:- 1200 – 1440 ft/sec iii- Rifle:- 2000 – 3500 ft/sec 2- Forces present in the medium a- Air resistance b- Gravity

  30. Forces originating from the projectile Velocity 1- Speed or Rate of motion also called Muzzle velocity • Rifles upto 2000 – 3000 fps 2- Direction of motion • Forward motion • Also Rotational motion in bullets due to rifling • 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.

  31. DEFINITIONS • YAW: is the oscillation around the long axix of the bullet. • PRECESSION: is a circular Yaw about the center of gravity which takes the shape of a decreasing spiral. • Nutation: is a rotational movement in a small circle which forms a rosette pattern like a spinning top.

  32. Forces present in the medium 1- Air resistance 2- Gravity Projectile Follows.. Curved path Trajectory of bullet

  33. Trajectory of bullet

  34. Tail wag phenomenon • Inside barrel projectile is supported by walls of barrel • Entering new medium loses balance due to air resistance & force of gravity • Regains balance after covering some distance Tail wag Initial tail wag Terminal tail wag Intermediate tail wag

  35. Bullet through a glass Intermediate tail wag Secondary misslies

  36. Tail wag phenomenonFor pistol up to 60 yardsFor Rifle up to 200 yards Medicolegal importance Atypical firearm entry wounds

  37. Terminal / Wound Ballistics “ It is concerned with the effect of bullet on the target at impact until it comes to rest “ by Naseeb R. Awan Mechanism of Wound production Laceration & Crushing Shock waves Cavitation

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