Firearm Injuries

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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 ($KE = 1/2 mv^2$).

Bullet components and types diagram

⭐ 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.

Firearm wound characteristics with satellite wounds

⭐ 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.

3D CT reconstruction of firearm wound trajectories

  • 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.
  • 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.

  • 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_

Practice Questions: Firearm Injuries

Test your understanding with these related questions

The tests which usually help in determining the gunshot residue on clothing include all of the following, except:

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Flashcards: Firearm Injuries

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CSF is mixed with blood and collected on a piece of filter paper shows a central red spot (blood) and a peripheral lighter halo, also known as _____ sign

TAP TO REVEAL ANSWER

CSF is mixed with blood and collected on a piece of filter paper shows a central red spot (blood) and a peripheral lighter halo, also known as _____ sign

Double target/halo

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