THE CONTEXT
Wound shape is influenced by the skin surface and blade orientation, while differences in depth and margin configuration help indicate the direction of cutting.
Surface and blade effects on shape
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An incised wound may follow a zig-zag course in loosely attached skin, such as the axillary fold, because the blade pushes the skin ahead before cutting it.
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A curved blade produces crescentic edges. A straight blade can also produce a crescentic wound on a convex surface, such as the occipital region or buttocks.
Haemorrhage
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Haemorrhage is greater because vessels are cut cleanly. The passage describes increased bleeding after complete arterial division because of inability to contract or retract.
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Cutting an artery produces spurting of blood.
Head and tail of the wound
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The beginning is deeper because greater pressure is exerted on the knife; this deeper beginning is the head of the wound.
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Toward the end, the cut becomes progressively shallower until only skin is cut as the knife leaves the tissues. This tailing indicates the direction in which the cut was made.
Bevelling and flap wounds
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Oblique blade entry produces a bevelled margin on one side and undermining on the other, exposing subcutaneous tissue and indicating the direction of blade entry.
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A nearly horizontal blade produces a flap wound. Bevelling is produced only by a sharp weapon.