Ballistic Injuries

Ballistic Injuries - Guns & Ammo

• Firearms Types:
  • Rifled: Impart spin to bullet (e.g., rifles, pistols).
    • Lands & Grooves: Helical grooves inside barrel.
  • Smoothbore: No rifling (e.g., shotguns).
• Ammunition Components:
  • Bullet/Projectile: The missile.
  • Cartridge Case: Contains other components.
  • Propellant (Gunpowder): Produces gas to propel bullet.
  • Primer: Ignites propellant.

⭐ Caliber: Internal diameter of a rifled barrel, measured between opposing lands (e.g., 0.38 inch). For shotguns, Gauge is used: number of lead balls, each of bore diameter, that make up 1 pound (e.g., 12 gauge means 12 lead balls of that diameter weigh 1 pound; smaller gauge number = larger barrel diameter).

Ballistic Injuries - Impact & Injury

• Mechanism of Injury:
  • Direct tissue laceration & crushing.
  • Temporary Cavity: Rapid tissue stretch due to energy transfer. Can be 30-40x bullet diameter. Major damage mechanism in high-velocity wounds.
  • Permanent Cavity: Actual tissue destruction path.
• Kinetic Energy (KE): $KE = 1/2 mv^2$. Energy transfer dictates wound severity.

  ⭐ Velocity is the most critical factor determining wounding potential, significantly more than mass.

• Factors Influencing Injury:
  • Projectile: Velocity (most critical: High-velocity projectiles generally exceed 2000 ft/s, though exact thresholds vary by context and weapon system), mass, design (e.g., hollow-point, frangible ↑damage), deformation (tumbling, yawing, fragmentation).
  • Tissue: Density & elasticity. Muscle, liver, brain highly susceptible to cavitation. Bone fragments act as secondary projectiles.

Ballistic Injuries - Hole Story

Entry vs. Exit Wounds

• Contact Shot:
  • Muzzle impression.
  • Soot/charring in track.
  • Stellate tears (bony areas).
• Close Range Shot (up to ~15 cm):
  • Soot, burning, dense tattooing.
  • 📌 Mnemonic: SBT (Soot Burns Tattooing).
• Intermediate Range Shot (~15 cm to ~2 m):
  • Tattooing (stippling) present.
  • No soot/burning. Abrasion collar.
• Distant Range Shot (>2 m):
  • Abrasion collar only.
  • No soot, burning, tattooing.

⭐ Abrasion collar (bullet wipe) is a key indicator of an entry wound, even in atypical presentations like tangential wounds.

Range of Fire Determination:

Ballistic Injuries - Clues & Conclusions

• Weapon ID: Modern forensic analysis focuses on elemental ratios of bullet composition to identify origin; wadding material analysis determines shot size range; bullet striations (rifling) for traditional identification.

• Range Estimation (critical):

  • Contact: Muzzle imprint, charring, soot in wound.
  • Close (<15 cm): Soot, burning, dense tattooing.
  • Intermediate (15-60 cm): Tattooing (powder stippling), no soot.
  • Distant (>60 cm): Abrasion collar only.

• Direction of Fire:

  • Entry: Smaller, inverted edges, abrasion collar.
  • Exit: Larger, everted edges (if present).
  • Bone: Internal beveling (entry), external (exit) - high-velocity/deforming bullets may cause atypical presentations.

• Manner: Site, range, circumstances, number of shots under BNS homicide provisions.

⭐ Gunshot Residue (GSR): Lead (Pb), Antimony (Sb), Barium (Ba). Detection window varies significantly based on activity, environmental conditions, and analytical method; modern techniques consider wider variables beyond traditional 4-6 hr guideline.

High‑Yield Points - ⚡ Biggest Takeaways

• Entry wounds: typically smaller, circular, with abrasion collar and grease collar.
• Exit wounds: usually larger, irregular, everted, and lack these collars.
• Contact wounds: show muzzle imprint, charring, soot. Close-range (up to ~30 cm) adds tattooing.
• Distant wounds (beyond ~60 cm) only feature the bullet hole and abrasion collar.
• Skull: Internal beveling at entry, external beveling at exit. Keyhole defects for tangential impacts.
• Yawing, tumbling, ricochet, or tandem bullets cause atypical, often larger, wounds.