L6: Firearm Injuries Flashcards
Def of Firearm weapon
- Specialized device designed to propel a projectile (shot/bullet missile) by expansive force of gases generated as a result of combustion of the propellent (gun powder) at its base.
Structure of rifled cartridge
Any cartridge consists of a case holding all parts togetber.
-The top has a projectile (bullet)
- The base has a percussion “primer” cap
- The space between projectile and percussion cap is filled with a propellant (e.g. gunpowder).
Functions of Rifling
The idea of riflings is to force bullet from muzzle in a spiral manner (rotating on its longitudinal axis) to:
- Diminish resistance of air & gravity to the bullet.
- Give it longer range of travelling.
- Give it more power of penetration.
- Increase stability of the bullet & prevent it from wobbling.
what are Firearm weapons composed of?
Classification of Firearm weapons
Def of Rifling
Riflings mean “longitudinal ridges alternating with grooves, running spirally on inner surface of barrel parallel to each other”.
Characters of Rifling
- Riflings vary in number, direction (either clockwise or anticlockwise), depth and width.
- Rifling is individual for each weapon
“ so, no two weapons have the same rifling. - Rifling leave on surface of the fired bullet “rifling marks” which are oblique parallel grooves of same number, depth, breadth and direction as the riflings
Composition of the firearm cartridge
1) Bullet
2) Case
3) Gunpowder
4) Base
5) Percussion cap.
what is a bullet made of?
- It’s usually made of lead,
- which may have a jacket made of strong metal (copper or nickel), so named “jacketed bullets”
Shape of bullets
It’s conical in shape to ensure least air resistance.
Types of bullets
- Semijacketed
- Open tip
- Dumdumised “Dum Dum”
- Explosive
- Soft point
- Hollow point
- Boat tail
- Frangible bullets.
Def of Rubber Projectiles
- They are rubber or rubbor-coated projectiles that can be fired from riot guns.
Usage of Rubber Projectiles
- They are used extensively for riot control.
- They are intended to be a non-lethal altornalive to metal projectiles.
Characters of Rubber Projectiles
Pattern of firing of Rubber Projectiles
- It should not be fired at a distance less than 20 meter.
- Policemen are instructed to fire at lower half of the body, to avoid the more serious injuries arising from hitting head or chest.
Definition of Shots
- These are lead pellets are used in non-rilled weapon, which may be machine-made or home-made shots.
MLI of Shots
- Their presence denotes that the wound is a firearm injury.
- They give an idea about type of the weapon used.
- They give an idea about distance of firing (diameter of area of dispersion of shots).
Def of Gun powder
- It lies between the percussion cap and the projectiles (bullets or shots).
- Its ignition leads to formation of hot gas under pressure.
Types of Gun powder
- Gun powder is of 2 types, black powder & smokeless powder.
MLI of Gun powder
The sequence of events on firing a cartridge
- Flash of light
- Hot explosive gases
- Flame and smoke
- Unburnt powder particles
- Missiles or projectiles
Flash of light
- Seen before hearing the sound of explosion.
Hot explosive gases
- Come out from the muzzle due to ignition of gun powder.
- Travel to a distance of 15 cm., so its. effect is apparent in near firing only.
- They form explosion leading to an inlet which is Lacerated, irregular with everted edges.
Flame and smoke
- Flame produces burning of the edges of the inlet and singing of hair around it.
- Smoke produces blackening of skin around the wound (can be easily washed out with water).
Unburnt powder particles
- These particles are embedded in the skin around inlet
- (so they cannot be washed with water like blackening) producing “Tattooing”, which is more apparent with black powder.
The distance of firing of bullets is judged by ….
- Power of its penetration
- Presence of powder marks.
Wads Firearm injury
- They come out of the muzzle, which may be found inside or outside body of victim depending on the distance of firing.
Describe firearm injury due to Shots
Characters of firearm wounds
- Loss of substance
- Presence of powder marks
- Presence of two wounds
- Bevelling
Loss of substance firearm wounds
- It is the most important feature of firearm injuries, which differentiates it from all other types of wounds.
- This loss of tissue is due to great kinetic energy of missiles.
Presence of two wounds firearm wounds
(Inlet and Exit) unless missile is retained inside the body.
Presence of powder marks firearm wounds
As blackening, burning and tattooing.
Bevelling firearm wounds
When the bullet hits a flat bone (e.g., skull, sternum and pelvis),
- Entry wound is called internal bevelling “Punched -in-hole
- Exit wound is called external bevelling “Punched-out-hole”.
Differences between inlet and exit firearm wounds
what causes atypical firarm inlet?
due to multiple reasons, most commonly atypical inlet is inflicted depending on:
- Site of the wound (Scalp - Corrugated skin)
- Distance of firing (Contact - near - far)
scalp inlet firaem wound
- Stellate inlet wound, due to back pressure of gases in near firing.
inlet firearm wound in corrugated skin
Skin of neck, axilla and scrotum,
Inlet is irregular.
Classification of inlet wounds according to distance of firing
- Contact inlet
- Near inlet
- Far inlet
what causes contact inlet?
It results when the muzzle of the weapon is pressed against the skin.
shape of Contact Inlet Wound
- The wound is circular, unless the missile is fired with the gun at an angle.
- There is usually a thin band of contusion in the margin of wound (Muzzle imprints)
- The hair is singed in contused area.
- The margin of the wound shows burning or even charring by flame causing dehydration and toughening of the margins.
- A thin rim of abrasion is shown around wound and covered with powder residue.
- Tattooing is minimal or absent.
Shape of Contact Inlet Wound if the gun is held tightly against the skin
- no powder marks is seen on the external surface but they are present within subcutaneous tissue and in bullet tract.
shape of Contact Inlet Wound If there is bone immediately under the skin
- gun powder blackening is frequently seen on surface of bone around bullet hole.
Characters of Near inlet wound
- Near firing inlet is inflicted when range of firing is less than two meters.
- It shows all powder marks.
Characters of far inlet wounds
- Such wound results when the range of firing is greater than two meters, With absence of all powder marks.
