A 28-year-old male victim of a suspected homicide presents with a single gunshot wound to the abdomen. The entry wound is 8 mm in diameter with beveling of the inner surface. The exit wound is 25 mm in diameter with beveling of the outer surface. Which investigation is most appropriate to confirm the direction of the bullet and differentiate entry from exit wound?

Explanation

## Entry vs. Exit Wound Differentiation ### Beveling Pattern as Diagnostic Feature **Key Point:** Beveling of wound margins is the most reliable macroscopic feature to differentiate entry from exit wounds. Entry wounds show beveling of the INNER surface (inward bevel), while exit wounds show beveling of the OUTER surface (outward bevel). ### Comparative Morphology of Entry and Exit Wounds | Feature | Entry Wound | Exit Wound | |---|---|---| | **Size** | Smaller (≈ bullet diameter) | Larger (> bullet diameter) | | **Shape** | Circular/oval | Irregular/stellate | | **Margins** | Clean, punched-out | Everted, ragged | | **Beveling** | Inward bevel (inner surface) | Outward bevel (outer surface) | | **Abrasion collar** | Present (inverted cone) | Absent | | **Soot/Tattooing** | May be present | Absent | | **Tissue flap** | Inward | Outward | **High-Yield:** Inward beveling at entry wound occurs because the bullet creates a cone of compression as it penetrates, pushing tissue inward. Outward beveling at exit occurs as the bullet exits and tissue is pushed outward by the projectile. ### Mechanism of Beveling Formation 1. **Entry wound:** Bullet compresses tissue radially inward → creates an inverted cone → inner surface beveled. 2. **Exit wound:** Bullet exits with kinetic energy → tissue pushed outward → outer surface beveled. 3. **Direction determination:** Beveling pattern directly indicates bullet trajectory. **Clinical Pearl:** Beveling is visible on the outer surface of skin and on cut edges of bone. In skeletal injuries, beveling of bone is even more pronounced and diagnostic. ### Why Macroscopic Examination is Superior - **Direct visualization:** Beveling pattern is immediately apparent without additional processing. - **Cost-effective:** No expensive imaging or laboratory analysis required. - **Reliable:** Beveling is pathognomonic for entry/exit differentiation. - **Legal admissibility:** Accepted as standard forensic evidence. - **No artifact:** Unlike imaging, macroscopic examination is not affected by imaging artifacts or reconstruction errors. **Mnemonic:** **IN-OUT** = **IN**ward bevel (entry), **OUT**ward bevel (exit).