Wound severity, forensic interpretation and the definition of abrasion
THE CONTEXT
Injury severity depends on tissue properties and the circumstances of impact. These variations limit precise forensic estimates of the force used.
Gas and fluid effects
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Gases are readily compressible, allowing extensive lung compression without structural injury. Sudden violent compression can nevertheless generate damaging pneumostatic forces.
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Force transmitted through a fluid-containing structure, such as the stomach or bladder, displaces fluid away from the contact area and may produce tissue laceration.
Factors modifying severity
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A weapon that deforms or breaks on impact consumes some energy in that process, reducing injury.
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Movement of the body with a blow increases the time over which energy is delivered and reduces severity.
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A larger contact area dissipates force. A flat weapon surface therefore produces less severe injury than a narrow object.
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A projecting part concentrates force at its tip and can produce a more severe wound.
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The same force may cause more severe injury over a rounded region, such as the top of the head, than over a flat region, such as the back.
Forensic interpretation
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Equal forces applied to the same region under different circumstances may produce different wounds.
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Minor forces may cause severe wounds, while relatively severe forces may cause minor wounds.
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The force used cannot often be determined scientifically from a particular wound, and damage cannot be predicted precisely from a given force. Medical opinions should use broad qualified terms.
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Internal organ injuries may occur without external signs of damage.
Abrasion
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An abrasion, also termed gravel rash, is destruction of skin that usually involves only the superficial epidermal layers.