Autopsy demonstration of bruises and effects of decomposition
THE CONTEXT
Bruises may require dissection for detection, while decomposition can obscure the distinction between trauma and postmortem blood pooling.
Margins and decomposition
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Postmortem bruises usually have sharply defined margins. Antemortem bruises generally have less sharp or indistinct margins, indicating vital reaction.
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In a body lying on its back, gravity causes blood to accumulate in the posterior or dependent scalp.
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Decomposition causes red-cell haemolysis and diffuse soft-tissue discolouration. Leakage and haemolysis in hypostatic tissues can resemble the haemolysis in a contusion, making antemortem contusion indistinguishable from postmortem hypostasis.
Methods of demonstration
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Postmortem lividity and dark skin colour may obscure bruises at autopsy.
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Scalp contusions are demonstrated by reflecting the scalp and incising it from the aponeurotic surface. Neck contusions are demonstrated by reflecting the neck structures in layers.
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Parallel skin incisions may reveal subcutaneous contusions; deep incisions into muscles reveal deep bruises.
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When doubt remains, a tissue portion should be taken for microscopy.
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Dissecting skin away from underlying fat and muscle fascia reveals the extent of bruising and underlying soft-tissue and muscle injury.
Medicolegal relevance
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Patterned bruises may connect a victim with an object or weapon, such as a whip, chain, cane, ligature or vehicle.
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Bruise colour changes may assist assessment of injury age.