Background. A review of the literature reveals many cases involving gunshot wounds altered by fire. The burning process can cause severe morphostructural changes (such as splits, shrinkage, crumbling) that are capable of altering or obscuring gunshot residue evidence and of producing post-mortem heat lesions on the skin, similar to gunshot wounds. Aim of the study. The present study is aimed at evaluating and comparing the amount and differential distribution of gunshot residue (GSR) through the analysis of unburned and burned gunshot wounds, performed with a microcomputed tomography (Micro-CT) technique. Materials and methods. Thirty-six experimental shootings at three different firing distances (5,15 and 30 cm) and 12 stab wounds, produced by a pointed instrument, were inflicted on human calves. Twenty-four specimens (6 for each tested distance and 6 for the stab wounds) were formalin-fixed, while the other were placed inside a wood-burning stove (4 minutes, 400°C), before formalin fixation. Each entrance and exit wound was sampled, cutting a parallelepiped specimen (1 x 1 x 2,5 cm) of epidermis, dermis and subcutaneous fat, surrounding and including the substance defect. All specimens were scanned using a Skyscan 1172 High Resolution Micro-CT, analyzing only particles with a density higher than 1000 HU, assumed to be GSR. Each sample was stained with hematoxylin–eosin and examined with a Leica DM-4000B optical microscope. Statistical analyses were performed using a two-way- and a one-way-ANOVA test. Results. As the unburned samples were easily recognizable, the visual and histological investigation on the burned samples cannot distinguish the entrance gunshot wounds from the stab wounds or the exit wounds. In the unburned specimens the Micro-CT analysis detected particles with a density higher than 1000 HU on the epidermis layer around the hole and on the dermis layer. In burned samples the GSR was detected only in the dermis layer. In burned and unburned samples GSR particles were not detected in either the stab wounds or in the exit holes. Statistical analysis reveals that GSR percentage was in inverse ratio to firing distance with a non-linear fashion and was abated after the burning process. Discussion and Conclusions. Micro-CT is a useful screening for the study of charred wounds, capable of distinguishing gunshot entrance wounds from the exit wounds or other similar lesions. Further examinations, even in different experimental conditions (temperature, time of exposure), are necessary in order to corroborate the correlation between firing distance and GSR percentage on samples damaged by fire.
Micro-CT analysis of gunshot residue in firearm wounds damaged by fire
Fais, Paolo;
2012-01-01
Abstract
Background. A review of the literature reveals many cases involving gunshot wounds altered by fire. The burning process can cause severe morphostructural changes (such as splits, shrinkage, crumbling) that are capable of altering or obscuring gunshot residue evidence and of producing post-mortem heat lesions on the skin, similar to gunshot wounds. Aim of the study. The present study is aimed at evaluating and comparing the amount and differential distribution of gunshot residue (GSR) through the analysis of unburned and burned gunshot wounds, performed with a microcomputed tomography (Micro-CT) technique. Materials and methods. Thirty-six experimental shootings at three different firing distances (5,15 and 30 cm) and 12 stab wounds, produced by a pointed instrument, were inflicted on human calves. Twenty-four specimens (6 for each tested distance and 6 for the stab wounds) were formalin-fixed, while the other were placed inside a wood-burning stove (4 minutes, 400°C), before formalin fixation. Each entrance and exit wound was sampled, cutting a parallelepiped specimen (1 x 1 x 2,5 cm) of epidermis, dermis and subcutaneous fat, surrounding and including the substance defect. All specimens were scanned using a Skyscan 1172 High Resolution Micro-CT, analyzing only particles with a density higher than 1000 HU, assumed to be GSR. Each sample was stained with hematoxylin–eosin and examined with a Leica DM-4000B optical microscope. Statistical analyses were performed using a two-way- and a one-way-ANOVA test. Results. As the unburned samples were easily recognizable, the visual and histological investigation on the burned samples cannot distinguish the entrance gunshot wounds from the stab wounds or the exit wounds. In the unburned specimens the Micro-CT analysis detected particles with a density higher than 1000 HU on the epidermis layer around the hole and on the dermis layer. In burned samples the GSR was detected only in the dermis layer. In burned and unburned samples GSR particles were not detected in either the stab wounds or in the exit holes. Statistical analysis reveals that GSR percentage was in inverse ratio to firing distance with a non-linear fashion and was abated after the burning process. Discussion and Conclusions. Micro-CT is a useful screening for the study of charred wounds, capable of distinguishing gunshot entrance wounds from the exit wounds or other similar lesions. Further examinations, even in different experimental conditions (temperature, time of exposure), are necessary in order to corroborate the correlation between firing distance and GSR percentage on samples damaged by fire.
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