Firearm Injury Flashcards
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What is Forensics Ballistics?
- Science dealing with investigation of firearms, ammunition + problem arising from their use
What are Firearms?
- Instrument which discharges a missile
- By the expansive force of gasses produced by burning an explosive substance
What is the Classification of Ballistics?
1) Internal = Study of firearms / projectiles, and their motion in the firearm
2) External = Study of firearms / projectiles after ejected from firearm
3) Terminal = Study of injuries produced by firearm
What are the Types of Firearms?
1) Rifled - such as Machine Gun, or Revolver
2) Smooth-Bore, aka Shot-Gun - either single / double barrelled
3) Air / Gas Operated
4) Country-Made
What is the Caliber?
- In Rifled Firearm = Distance measured by opposite lands / inner diameter of the barrel
- In Shot-gun = Equal to N.O of Pellets of Lead
What is the Cartridge?
- Outer Case where the explosives are stored together w/ the chemicals needed to ignite it
- Consists of = Case - Primer - Gun-Powder - Projectile / Bullet
Explain the Wound Mechanism of a Firearm
- Bullet produces an entry wound and a track EITHER with / without an exit wound
- Drilling Effect = Direct trauma via lacerating tissues, forming a permanent cavity (path of bullet in tissues)
- Temporary Cavity = Done by radial stretching around bullet track, from continued acceleration of the bullet - causing the wound cavity to be stretched outwards, but returned to their place soon after
- Deformation / Splitting of Bullet = In PARTS inside the tissues
What does the SEVERITY of the Firearm, depend on?
1) Tissue Disruption due to mechanical interaction BTW projectile + tissue
2) Effects of Temporary Cavity, produced by Projectile
What is “Range of Fire”?
- Distance between muzzle of firearm and target
Explain the Velocity & Mass of the Bullet
- KE = Wounds caused by the gunshot
- KE = 1/2 Mass x V^2
- Wounding Power = Amount of KE, transferred to the target
What’s the Relationship between Velocity and Kinetic Energy?
- KE is proportional to the Velocity
- Meaning, increased Velocity = increased KE
What happens if there’s a HIGH Velocity Rifle Wound?
- Additional Effect of Temporary Cavity Formation
- Due to large amounts of KE transferred to the tissue
What happens if the Temporary Cavity Pressure EXCEEDS the Elastic Limit of the Tissue?
- Organ disruption, aka “bursting effect”
- Organs with a LOW Density and HIGH Elasticity, are usually protected - e.g. Lung
What are the 4 Types of Ranges in a Rifled Firearm Wound?
1) Contact Range = Muzzle is in contact w/ the body
2) Close Range = Range is within the distance travelled by flame
3) Near Range = Within range of unburnt gun powder particles
4) Distant Range = Beyond Range of smoke, flame + gun powder particles
Define “Contact Range” and it’s wound
- Muzzle is in contact with the body
- Where flame-soot-gas-gunpowder particles are also in the track of wound
- Gases produced contain carbon monoxide, giving a cherry-red color of tissues in track
- Wound = large + cruciate - stellated / star-shaped
- Has a Muzzle IMPRINT
Define “Close Range” and it’s wound
- Within 5 - 10cm
- Wound = circular hole, surrounded by singeing / smudging
- ALSO see abrasion collar / grey collar / tattooing
- Tissues often appear cherry-red color
Define “Near Range” and it’s wound
- Entry wound = circular / oval
- ONLY see abrasion collar / grey collar / tattooing
Define “Distant Range” and it’s wound
- Entry wound = circular with inverted margins
- ONLY see grey collar + abrasion collar
- Exit wound = Edges are everted
What are the Characteristics of ALL Firearm Wounds?
- Oval Skin Defect that gapes open
- Abrasion Collar = Due to skin being scraped by bullet, as it passes thru
- Grey Collar = Bullet is dirty w/ grease, as it wipes off onto the skin
- Grey Collar OVERLAYS the Abrasion Collar
What are the Medico-legal Aspects of Firearm Injuries?
- Type of Firearm Used - whether if it’s rifled or smooth-bore
- Range of Fire - determined by the entry wound
- Direction of Fire
- Area of Firing
- Cause + Manner of Death
How is the DIRECTION of Fire interpreted?
- Projectile enters perpendicular = Wound will be circular
- Projectile enters oblique = Wound will be oval - collars + abrasions will become eccentric
What is a SUICIDAL Case of Firearm Injury?
- Entry Wound = Either head / chest
- Range = Either Contact / Close
- N.O of Wounds = Just One
- Firearm residue + weapon is present
- Suicide Note also present
What is a HOMICIDAL Case of Firearm Injury?
- Entry Wound = Anywhere
- Range = Anywhere
- N.O of Wounds = Multiple Shots are made
- Find other injuries to the body
