CDI 2

• FIREARM - mechanical device that uses pressure from a burning powder to force a projectile through and out of a metal tube.
• Ballistics - the study of a projectile in motion.
• TWO PRINCIPAL COMPONENT PARTS:

  • The firearm - the instrument for the propulsion of a projectile by the expansive force of gases from a burning gunpowder
  • The cartridge or ammunition a complete unfired unit consisting of bullet, primer, cartridge case and powder charge.
• Cartridge case or shell


  cylindrical structure with a base which houses the powder
• Primer

  • transformation of mechanical energy by the hit of the firing pin (function)
  • located and sealed at the cartridge base
  • containing lead, barium, antimony (LAB)
  • hits the anvil which causes the generation of a flash which in turn ignites the powder (cause a spark)
• Gunpowder or propellant


  primary propulsive force in a cartridge when exploded, will cause the bullet to be driven forward towards the gun muzzle
• • Black powder - (charcoal, sulphur, potassium nitrate) now obsolete
  • Smokeless powder - (nitrocellulose with/without nitroglycerine)
  • Semi smokeless powder - Mix of 85% black and 15% smokeless powder
• Bullet (slug, missile, projectile)


  metallic object attached to the free end of the cylindrical tip of the cartridge case

  propelled by the expansive force of the propellant
• MECHANISM OF FIREARM ACTION

  1. Pulling the trigger releases the firing pin…
  2. The firing pin strikes the primer…
  3. The primer ignites the gun powder…
  4. The powder generates gas that propels the bullet forward through the barrel & ejects the spent cartridge case.
• Abrasion collar (contuso-abradded collar, marginal abrasion) - pressure of the bullet on the skin will cause the skin to be depressed
• Smoke (soot, smudging, fouling, smoke blackening)

  • totally/ complete combustion of the gunpowder
  • near shot/firing (1 foot, 12 inches distance)
  • It is merely deposited on the target and readily wiped off
• Powder tattooing (stippling, peppering)

  • partially combustion/ partially burned powder
  • cannot be removed by ordinary wiping
  • the wound of entrance up to distance of 24 inches
• Beveling (cone-shape deformity)- caused by the forward moving force of the bullet, which creates a “cone-shaped” deformity as the bullet pushes through the layers of bone.
• Keyhole Defect - bullet strikes the skull at a very shallow angle it may produce an entrance wound with both internal and external beveling
• Graze - when a bullet scrapes or grazes over the skin without penetrating more deeply, usually elongated to oval in appearance and may have marginal tears at the edges.
• Estimated RANGE OF FIRE OF GUNSHOT WOUNDS

  • Contact range - muzzle in contact with body (muzzle imprint) 1 foot
  • Close range - (near shot, medium) within 3 feet
  • Distant range - greater than 3 feet
• Contact fire - muzzle in contact with body (or a very short distance - a few centimeters - from body)
• Short Range Fire

  • (1 to 15 cm distance)
  • Powder tattooing is present (dense and limited dimension of spread)
  • Abrasion ring or collar is present (contact ring)
• Medium Range Fire

  • (more than 15 cm but less than 60 cm)
  • Gunpowder tattooing is present but of lesser density and has a wider area of distribution
• Fired More Than 60 cm Distance

  • Wound of entrance has no burning, smudging or tattooing.
  • Contact ring is present
• ASPHYXIA - the supply of oxygen to blood and tissues has been reduced
• the brain has been deprived of oxygenated blood for period of:

  • at least 6 minutes brain damage is probable;
  • over 10 minutes, brain damaged is certain.
• PHASES OF ASPHYXIAL DEATH

  • Struggle or Dyspneic phase - due to the lack of oxygen and the retention of carbon dioxide in the body the breathing becomes rapid and deep the face, hands and fingernails become bluish
  • Quiescence phase - victim becomes unconscious, almost lifeless
  • Convulsive phase - due to the stimulation of the nervous system by carbon dioxide cyanosis becomes more pronounced and the eyes become staring and the pupils are dilated
  • Apneic phase - breathing becomes shallow and gasping and the rate becomes slower till death
• TARDIEU SPOTS - examination of the visceral organs shows small petechial hemorrhages
• GENERAL FEATURES

  1. Cyanosis - bluish discoloration of face, extremities, internal organs seen soon after death.
  2. Congestion / Tissue edema - due to venous congestion and poor venous return to the heart
  3. Petechial haemorrhages - due to raised pressure in the microvasculature.
  4. Other findings - increased fluidity of blood with veins and right heart distended with fluid blood
• ASPHYXIA BY HANGING - violent death brought about by the suspension of the body by a ligature
• STRANGULATION BY LIGATURE - produced by compression of the neck by means of ligature which is tightened by a force other than the weight of the body
• MANUAL STRANGULATION OR THROTTLING - the constricting force applied in the neck is the hand
• SPECIAL FORMS OF STRANGULATION:

  1. Palmar strangulation - the palm of the hand of the offender is pressed in front of the neck without employing the fingers.
  2. Garroting - a ligature, a metal collar or a bowstring is placed around the neck and tightened at the back. a mode of judicial execution during the 19th century
  3. Mugging (strangled hold) - the assailant standing at the back and the forearm is applied in front of the neck.
• ASPHYXIA BY SUFFOCATION - exclusion of air from the lungs by closure of air openings or obstruction of the air passageway
• SMOTHERING - caused by the closing of the external respiratory orifices, either by the use of the hand or by some other means
• Overlying - result of obstruction of the nose and mouth by any part of the body
• Gagging - usually handkerchief; linen or other clothing matters to prevent air to have access through the mouth or nostrils
• Plastic bag suffocation - is when a plastic bag is placed over the nose and mouth
• CHOKING - form of suffocation brought about the impaction of the foreign body in the respiratory passage.
• Café coronary - sudden heart attack in the middle of his dinner
• ASPHYXIA BY SUBMERSION OR DROWNING - the nostrils and mouth has been submerged in watery or viscid fluid for a time
• Phases of drowning

  1. "respiration de surprise" - first phase, occuring at the moment when the mouth and nose are covered with fluid
  2. Phase of resistance - second phase, consist a short period of apnea due to the irritation of the sensory laryngeal nerve
  3. Dysnpneic phase - third phase, forceful respiratory movement
  4. Apneic phase - fourth phase
  5. Terminal respiration - fifth phase, the breathing stops permanently
• TIME REQUIRED FOR DEATH

  • 1-1/2 minutes is considered fatal a person
  • may survive even after 4 minutes of submersion
  • death in drowning is 2 to 5 minutes
• Findings suggestive that the person died of drowning

  • Presence of materials or foreign bodies in the hands of the victim
  • Clenching of the hands as a manifestation of cadaveric spasm or effort of the victim to save himself in drowning