A 32-year-old man is brought to the mortuary with a gunshot wound to the chest. The pathologist observes a small, round wound with an abrasion collar and minimal external bleeding, but the exit wound is large, irregular, and heavily bloodstained with tissue debris. Which feature best explains the difference in appearance between these two wounds?

Question

Accepted Answer

A. The entrance wound is smaller because the projectile is intact and concentrated; the exit wound is larger because the projectile has deformed and dispersed its energy over a wider area. ## Entrance vs Exit Wound: Projectile Dynamics and Tissue Damage

### Energy Transfer and Wound Morphology

**Key Point:** The entrance wound reflects the projectile's initial state (intact, concentrated energy), while the exit wound reflects the projectile's final state (deformed, energy dissipated through tissue).

### Comparison Table

| Aspect | Entrance Wound | Exit Wound |
|--------|---|---|
| **Projectile state** | Intact, high kinetic energy concentrated | Deformed, fragmented, energy spent |
| **Wound diameter** | Small, matches projectile caliber | Large, exceeds projectile diameter |
| **Wound shape** | Round/oval (perpendicular impact) | Irregular, stellate, variable |
| **Tissue damage** | Minimal, confined to tract | Extensive, cavitation zone |
| **Bleeding** | Minimal (tract sealed by projectile) | Heavy (large defect, tissue destruction) |
| **Abrasion collar** | Present (~95% of cases) | Absent |

**High-Yield:** The exit wound is larger and more destructive because:
1. The projectile has **deformed** (mushroomed, fragmented, or tumbled)
2. **Cavitation** has occurred — temporary and permanent wound cavities expand tissue damage
3. **Secondary projectiles** (bone fragments, clothing) add to tissue destruction
4. The projectile's **energy is nearly exhausted**, causing explosive tissue disruption rather than clean penetration

### Why Entrance Wounds Appear Smaller

**Clinical Pearl:** An intact projectile creates a clean, confined tract. The abrasion collar is produced by the projectile's friction on the epidermis, not by energy dissipation. The entrance wound diameter closely matches the projectile's caliber.

### Why Exit Wounds Appear Larger and Irregular

1. **Deformation:** The projectile has been flattened, fragmented, or destabilized
2. **Cavitation:** Temporary cavity expansion (up to 10× projectile diameter in high-velocity wounds) causes tissue tearing
3. **Secondary missiles:** Bone and clothing fragments exit with the projectile
4. **Tissue elasticity:** Exit wounds exploit the skin's elasticity, creating irregular, stellate margins

**Mnemonic:** **DEFECT** — Deformed projectile, Energy exhausted, Fragmentation, Extensive cavitation, Tissue tearing, Crater-like appearance

### Bleeding Pattern Explained

- **Entrance:** Minimal external bleeding because the projectile seals the tract and internal bleeding is contained within the body cavity
- **Exit:** Heavy external bleeding because the large defect cannot be sealed, and tissue destruction disrupts blood vessels

[cite:Reddy Forensic Medicine 33e Ch 8; Vij Textbook of Forensic Medicine & Toxicology 6e Ch 10]

Answer

B. The entrance wound is round because it is perpendicular to the skin; the exit wound is irregular because the projectile tumbles before exiting

Answer

C. The entrance wound has minimal bleeding because it is sealed by the projectile; the exit wound bleeds heavily because the projectile creates a larger defect

Answer

D. The entrance wound has an abrasion collar because of contact with clothing; the exit wound lacks this feature because the projectile exits faster

Explanation

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