Entrance Wounds Contact wounds characteristically have soot on the outside of the skin, and muzzle imprint, or laceration of the skin from effects of gases. Contact wounds of airguns usually lack these features (Cohle et al, 1987). Intermediate, or close-range, wounds may show a wide zone of powder stippling, but lack a muzzle imprint and laceration. The area of powder stippling will depend upon the distance from the muzzle. (Denton et al, 2006) Distant range wounds are lacking powder stippling and usually exhibit a hole roughly the caliber of the projectile fired. The most difficult problem is distinguishing a distant from a contact wound. The factors that can affect the amount and distribution of gunshot residue (GSR) on skin and clothing include: (1) firing distance, (2) length and diameter of the firearm barrel, (3) characteristics of the gunpowder, (4) angle between the firearm barrel and target, (5) characteristics of the cartridge, (6) the environment (moisture, wind, heat), (7) type of clothing, (8) intermediate targets, and (9) characteristics of the target (tissue type, putrefaction, blood marks) Scanning electron microscopy of entrance wounds shows gunshot residue within collagen fibrils. The entrance wound appears abraded, with loss of the papillary pattern and laceration of basement membrane! Computer assisted image analysis may aid detection of GSR Entrance wounds into skull bone typically produces bevelling, or coning, of the bone at the surface away from the weapon on the inner table. In thin areas such as the temple, this may not be observed. Sternum, iliac crest, scapula, or rib may show similar features. These observations may permit determination of the direction of fire. A small, dense projectile may punch out a rounded portion of cranium, while a larger projectile may produce circumferential fractures that radiate outward from the point of entrance. The pattern of fractures may permit identification of the sequence and direction of fire. Puppes rule states that when two or more fracture lines of the skull produced by different blunt forces intersect, it is possible to reconstruct the sequence of injuries. The presence of bone damage from an initial injury causes subsequent injuries to stop in the point of intersection with the previous wounds. In the skull, the fracture lines produced by a second gunshot stops at pre-existing fractures of the skull.
Posted on: Mon, 05 Jan 2015 19:48:59 +0000
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