Firearm Injuries

Introduction & Ballistics - Bullet Basics Bonanza

• Ballistics: Projectile motion study.
  • Internal: Within firearm (propulsion).
  • External: Flight to target (trajectory, spin).
  • Terminal (Wound): Target interaction, energy transfer.
• Firearms:
  • Smoothbore (Shotgun): Multiple pellets (shot).
  • Rifled (Rifle, Pistol): Single bullet; lands & grooves impart spin.
• Ammunition:
  • Bullet (projectile)
  • Cartridge case
  • Propellant (gunpowder)
  • Primer (ignition)
• Bullet Types:
  • Lead (L): Soft, deforms.
  • Jacketed: Lead core, metal jacket.
    • Full Metal Jacket (FMJ): Non-expanding.
    • Soft Point (JSP): Controlled expansion.
    • Hollow Point (JHP): Max expansion.
• Key Factors:
  • Calibre: Barrel/bullet diameter.
  • Velocity: Major wounding factor ($KE = 1/2 mv^2$).

⭐ Rifling marks (from lands & grooves) on a bullet are unique to a firearm barrel, vital for identification.

Wound Features - Impact Insights

• General Characteristics:
  • Shape: Round/oval (perpendicular impact), Elliptical (angled impact).
  • Size: Often smaller than bullet diameter due to skin elasticity.
• Key Entry Wound Features:
  • Abrasion Collar: Rubbing of bullet against skin.
  • Grease/Dirt Collar: Lubricant/dirt wiped from bullet.
  • Inverted Edges.
• Exit Wound Features:
  • Typically larger, irregular, everted edges.
  • No abrasion collar, soot, or tattooing.
  • May show fat herniation.

⭐ Bone Impact: Entry wounds show internal beveling; exit wounds show external beveling (Puppe's Rule for skull), though modern 3D imaging confirms trajectory analysis in complex cases with potential exceptions.

• Factors Influencing:
  • Bullet type (e.g., hollow-point causes larger wounds).
  • Tissue elasticity (e.g., bone vs. soft tissue).
  • Range of fire, intermediate targets, clothing significantly alter characteristics.
  • Advanced imaging techniques (CT scans, 3D reconstruction) enhance wound trajectory assessment.

Specific Weapon Wounds - Gunshot Gallery

• Shotgun Wounds:
  • Contact: Muzzle imprint, charring, soot/powder in wound.
  • Close Range (<2m): Single defect, scalloped edges, wads/pellets inside.
  • Intermediate Range (2-4m): Central hole + satellite pellets.
  • Distant Range (>4m): Pellet dispersion; pattern estimates range. Choke affects spread.
• Rifle Wounds (High Velocity):
  • Entry: Small, round/oval, abrasion collar, grease collar.
  • Exit: Larger, irregular, everted; often stellate over bone.
  • Key feature: Significant temporary cavitation causing extensive internal damage.
  • Keyhole defect: Tangential impact.
• Handgun Wounds (Lower Velocity):
  • Entry: Similar to rifle, often smaller. Abrasion/grease collar present.
  • Exit: If present, larger than entry; may be absent.
  • Less internal damage than rifles.

⭐ "Tattooing" (powder stippling) around an entry wound indicates a close-range shot (typically within 60 cm), but not contact.

Medico-legal Aspects - Forensic Firepower Facts

• Weapon Identification: Link weapon to crime via class & individual characteristics on bullets/cartridges.
  • Striations (rifling), firing pin marks, breech face marks, extractor/ejector marks.
• Range of Fire Estimation: Critical for event reconstruction.
  • Contact, close range (determined by GSR patterns and wound characteristics), intermediate, distant.
• Manner of Death Determination: Suicidal, Homicidal, or Accidental under BNS provisions.
  • Consider wound location, number, range, presence of suicide note.
• Evidence Integrity: Strict chain of custody per BNSS procedures for clothing, wads, bullets, GSR kits.

  ⭐ Tandem bullets (piggyback bullets): one bullet lodges in barrel, next one pushes it out; both may strike target.

High‑Yield Points - ⚡ Biggest Takeaways

• Entry wounds: smaller, abrasion collar, inverted edges. Exit wounds: larger, everted edges.
• Contact wounds: muzzle imprint, soot in wound, cherry-red muscle (COHb).
• Close range (e.g., <30cm): soot deposition, hair singeing, tattooing.
• Intermediate range (e.g., <2m): tattooing/stippling (powder burns) is characteristic.
• Distant range: only bullet hole with surrounding abrasion collar.
• Bone bevelling: internal for entry wounds, external for exit wounds.
• Shotgun choke dictates pellet spread; wad injuries possible at close range_