Range Determination in Decomposed Bodies

Determination as to whether a gunshot wound in a decomposing body is either close-range or distant can be difficult for a number of reasons. First are the changes of decomposition itself. Decomposition results in a blackish discoloration of the skin and subcutaneous tissue, which can either simulate or conceal soot. There is slippage of the epidermis, which can produce complete loss of powder tattooing and soot. Blood around the wound clots and dries out. Fragments of this desiccated blood can simulate partly burnt powder fragments.

In addition to the changes of decomposition, insect activity can obliterate as well as simulate wounds. Maggots and beetles are attracted to injury sites where blood is present. They can completely obliterate the entrance in the skin and thus any evidence of soot or powder. Insects can burrow into the skin, producing circular defects resembling gunshot entrance wounds. If there is subsequent drying of the edges, this may simulate the blackening and searing of a contact wound from a small caliber weapon (Figure 12.6).

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Figure 12.6 Hole in skin from insect burrowing. Note drying of edges which simulates contact wound.

Although nothing can be done if insects have obliterated a wound, it is possible to differentiate close-range versus distant wounds, provided that one has adequate instrumentation. In all decomposing bodies, the suspected wound should be examined in situ with the dissecting microscope for the presence of soot and powder. It should then be excised and the underlying subcutaneous tissue examined for soot and powder as well. In many instances, one cannot say with certainty whether soot is present. If one sees unburned powder grains, one will know that one is dealing with a close-range wound. As mentioned, fragmented, dried-out, desiccated blood can simulate partly burnt grains of powder. The suspected material can be submitted for analysis by thin-layer chromatography. This latter method can differentiate single-from double-base powder as well.17

After examination with the dissecting microscope, the wound can then be examined by EDX or SEM-EDX. Here one is looking for vaporized metal from the primer, cartridge case, and bullet deposited on the skin. Low levels of lead at an entrance are not significant in range determination, as the lead may have "wiped off" the bullet as it punched its way through the skin. This lead is either from the bullet itself or the primer residue that coats the fired bullet as it moves down the barrel.

Extremely high counts of lead found by EDX indicate close-range firing. The significance of specific levels or counts of lead depends on the time of counting and machine used and have to be worked out for each machine. Detection of either antimony or barium in significant levels of EDX indicates a close-range wound, as they are from the primer compounds. In addition, zinc and copper may be vaporized from the cartridge case; if this occurs in high enough concentrations, it will indicate close-range wounds. One has to have a control sample from the adjacent skin to see what is the normal background for the previously mentioned metals detected.

In contact wounds from shotguns and rifles, only lead may be detected by EDX at the wound entrance. The other metallic elements of the primer may not reach the entrance site in high enough concentrations to be detected by this method of analysis.

After initial examination of a wound by EDX, the wound can be split down the center and the interior re-examined with a dissecting microscope for powder and soot. Examination of the wound track by EDX should be carried out as the original EDX analysis detected trace metals deposited on the skin rather than in the wound track. Again, the presence of extremely high levels of lead or the presence of antimony and barium by EDX indicates that a wound is close-range.

Determination that a defect in a body is a pseudo-gunshot wound caused by an insect, is usually made by examining the wound and attempting to follow its bullet track. Usually, the insect burrows down only to the subcutaneous tissue and it is obvious that one is dealing with an insect defect. These alleged gunshot wounds can also be examined by SEM-EDX.

Addendum

Use of automated SEM-EDX in suicides is probably not justified as it is more costly than FAAS and does not offer any significant advantage. Analysis by the author of 100 suicides using SEM-EDX revealed that no specific particles were identified on the hands in 47% of cases involving .357 Magnums; 47% of .38 Specials; 85% of .22's; 38% of .380's, and 25% of 9 mm's. Based on indentification of specific particles, their number and their distribution on the hands, positive tests consistent with firing a gun were present only in 27 to 33% of cases involving .357 Magnum's; 33 to 37% of .38 Special cases; 5% of .22's; 8% of .380's, and 8 to 25% of 9 mm's.

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