A 32-year-old man is brought to the emergency department with a gunshot wound to the left chest. On examination, the entry wound is 8 mm in diameter with a surrounding abrasion collar and marginal blackening. The exit wound on the right chest is larger and more irregular. Which of the following statements about firearm injuries is NOT true?

Explanation

## Distinguishing Entry and Exit Wounds in Firearm Injuries ### Entry Wound Characteristics **Key Point:** Entry wounds are typically smaller, more regular, and surrounded by an abrasion collar and marginal blackening. 1. **Abrasion collar (contusion collar)** — formed by friction between the bullet and the epidermis as it penetrates; always present in entry wounds 2. **Marginal blackening** — caused by oxidation of the bullet's metallic surface (copper, lead, or steel) as it scrapes the skin; indicates direction of entry 3. **Size** — usually 8–10 mm for standard bullets, corresponding to the bullet's diameter 4. **Shape** — typically round or oval, depending on angle of entry ### Exit Wound Characteristics **Key Point:** Exit wounds are generally larger and more irregular, but size and shape depend on tissue elasticity and bullet deformation. - Usually larger due to temporary and permanent cavity formation - More irregular and stellate (star-shaped) in elastic tissues (face, scalp, chest) - May be smaller than entry wound in inelastic tissues (bone, cartilage) or if the bullet has lost significant velocity - No abrasion collar or marginal blackening ### The Critical Distinction **High-Yield:** The statement "exit wound is ALWAYS larger and more irregular" is FALSE. Exit wound size depends on: - Tissue elasticity (elastic tissues → larger exits; inelastic tissues → smaller exits) - Bullet velocity and deformation - Distance traveled through tissue **Clinical Pearl:** In inelastic tissues (e.g., bone, dense connective tissue), the exit wound may be smaller than the entry wound, contradicting the general rule. ### Summary Table | Feature | Entry Wound | Exit Wound | |---------|-------------|------------| | **Abrasion collar** | Present | Absent | | **Marginal blackening** | Present | Absent | | **Size** | Smaller (usually) | Larger (usually) | | **Shape** | Regular, round/oval | Irregular, stellate | | **Tissue elasticity effect** | Minimal | Major (elastic → larger; inelastic → smaller) | | **Beveling** | Inward | Outward | **Warning:** Do NOT assume exit wounds are always larger — this is a common trap in forensic medicine exams. Tissue elasticity is the key variable.