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Forensic Medicine & Toxicology

Forensic Medicine & Toxicology

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Forensic Medicine & Toxicology

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  1. Forensic Medicine & Toxicology Firearm Wounds By Dr. AminaAfzalRao Demonstrator KMS Medical College, Sialkot

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

  3. Weapons are fashion accessories and easily available

  4. 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 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 Firearm wounds

  5. History of Firearms • Firearms came to Europe from China • To produce an efficient firearm, there are three basic criteria to be met. • Weapon should be capable of causing substantial damage • It should be reliable & convenient to use • It should be reasonably accurate • Reverend Alexander John Forsythe, in 1807, living near Aberdeen, Scotland, held the first patent for a percussion ignition system..

  6. History of Projectile weaponry • Earliest weapons: bow and arrow, crossbow, simple catapult to huge ballistics / trebuchet • Gunpowder developed in china 1500 yrs ago; came to Europe and from 14th century used as weapon • Gunpowder= Charcoal, Saltpetre (Potassium Nitrite), Sulphur • Earliest guns were cannons, front then breech loading • Early guns flintlock muzzle loading with 3 parts “lock, stock and barrel”

  7. AK-47 Assault rifleDeveloped: 1974Mikael Kalashnikov Caliber: 5.45mmMagazine capacity: 30Loaded weight: 3,600gKilling range: 1,350m Assault rifles

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

  9. 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

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

  11. 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).

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

  13. Firearms Luger 9mm Colt 45 9 mm Thompson 5.7 mm

  14. 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

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

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

  17. TYPES OF CHOKING OF BARREL OF SHOT GUN

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

  19. 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

  20. 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.

  21. 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 casesare 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)

  22. 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 CSAELESS CARTRIDGE

  23. Primer The major primer elements are Lead styphnate(Pb), Barium nitrate (Ba), or a 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)

  24. 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.

  25. Various types of Ammunition

  26. Powder Charge • Modern gunpowder, or "smokeless" powder, can contain up to 23 organic compounds (FBI study)Nitrocellulose is 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 .

  27. BLACK GUN POWDER

  28. 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.

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

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

  31. 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

  32. 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.

  33. DEFINITIONS • YAW: is the oscillation around the long axix of the bullet. • PRECESSION: is a circular Yawabout 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.

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

  35. Trajectory of bullet

  36. 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

  37. Bullet through a glass Intermediate tail wag Secondary misslies

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

  39. 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

  40. Mechanism of Wound production

  41. Laceration & Crushing Kinematicsis the science of motion. In gunshot wounds we can use this to determine the extent of injury from the forces and motion involved. • Velocity is a key factor to the overall extent of gunshot wounds • According to the kinetic energy equation: (kinetic energy = mass/ 2 x velocity2) Doubling the mass doubles the energy, however doubling the velocity quadruples the energy • Therefore a small-caliber bullet traveling at high speed can produce a more extensive injury than larger caliber bullet traveling at a lower speed

  42. Laceration & Crushing….produced by the direct effect of bullet 1- Missile velocity 2- Shape & composition of projectile or Frontal area 3- Angle of impact 4- Flight characteristics as yaw, tumbling & nutation 5- Fragmentation

  43. LOW VELOCITY BULLET • PART STRUCK SOFT AND ELASTIC TISSUE • PUSHES & STRETCHES THE SKIN & UNDERLYING TISSUE. • ROTATES UPON ITS AXIS • INDENTATION IS PRODUCED • PERFORATION OF TISSUE • PASSAGE OF BULLET • ENERGY OF BULLET RADIATES LATERALLY • DAMAGE PROPORTIONATE TO DIAMETER OF THE BULLET • REPRESENTED BY THE PATH OR TRACK OF THE BULLET

  44. SHOCK WAVES • DEMONSTRATED ONLY BY HIGH SPEED PHOTOGRAPHY OR RADIOGRAPHY • IN HIGH VELOCITY BULLETS • TRACK IS FORCED THROGH SOLID TISSUE. • MEDIUM IS COMPRESSED BY MISSILE IN FRONT OF IT • REGION OF COMPRESSION MOVES AS A SHOCK WAVE OF SPHERICAL FORM, 4800/FT/S • CHANGES OF PRESSURE REMAINS FOR A MILLIONTH OF SECOND BUT MAY REACH PEAK VALUE UP TO 100atm. • So damage at a distance from wound track. • Solid tissues like Muscle, Liver, Spleen & brain are very susceptible. • Conducted particularly well along tube filled tubes like arteries & veins to cause damage at a distance.

  45. Shock Waves Shock waves…. generated in tissues by high velocity bullets, greater than 2,500/feet/sec • Last only for 15-25 microseconds • Are of high energy creating over 1000 lbs/sq inch of pressure • Easily rupture gas filled organs

  46. Types of cavitations • Temporary: • Permanent: • High velocity missile • Main destructive effect • Release of energy, absorbed by the local tissue. • Accelerated violently forwards & outwards. • Continue to move even after passage of missile. • A large cavity is produced (temporary cavity), reaches its maximum size, have sub atmospheric pressure, collapses in a pulsatile fashion and permanent cavity left. • Soft tissues pulped, blood vessels disrupted and bone may be shattered.

  47. Cavitation…. created by the bullets travelling at speeds > 1000 ft/sec • Size & shape depends upon the capacity of the bullet to disperse energy in the surrounding tissues • Tissues are moved forward & laterally away from the bullet • Continues for few milliseconds after bullet has passed • This creates a cavity which sucks air in from entry & exit wounds & may be 30 times more in diameter than that of the bullet • Permanent cavity if exists is much smaller than the temporary cavity

  48. M/L Importance of Wound Ballistics 1- Recognition of Entry & Exit wounds 2- Distance of Fire 3- Direction of fire & Wound track 4- Relative position of weapon/victim & angle of fire 5- Cause of death 6- Manner of death 7- Identification of firearm

  49. Components of a Shot responsible for damage 1- Shot charge (bullet/pallet) 2- Flame & heat 3- Hot explosive gases 4- Smoke 5- Wad 6- Unburnt gun powder 7- Grease from the barrel

  50. All these elements affect: • Body of the victim as signs & symptoms • At the place of strike or target produce characteristic changes • Result is FIREARM WOUND COMPLEX • This has two components: • Wounding component • Non – wounding component