ORIGINAL ARTICLE
Examination of Ricochet Gunshot Wounds From Commonly Encountered Surfaces Leigh Hlavaty, MD,*† Sarah Avedschmidt, MD,‡ Kelly Root,*† Jeffrey Amley,§ and LokMan Sung, MD*† Abstract: Proper interpretation of gunshot wounds is vital for the forensic pathologist and requires experience and expertise, as well as consultation with a firearms and ballistics expert and careful scene investigation in cases of atypical gunshot wounds. This study is the first large-series examining ricochet gunshot wounds involving different firearm calibers. Typical gunshot wounds created from 4 handgun calibers (22 Long Rifle, 9 19 mm Parabellum, .40 Smith &Wesson, and .45 Automatic Colt Pistol) and 2 rifle calibers (5.56 and 7.62 mm) were compared with wounds caused by bullets of those same calibers ricocheting off commonly encountered surfaces (concrete, asphalt, aluminum traffic signs, clay brick, and dry wall). Porcine skin, a human skin analog, attached to sheets of cardboard serviced as witness panels for capturing the entrance wounds. Examination of over 150 handgun and rifle entrance wounds established that every caliber and every ricochet surface resulted in atypical features, including irregularity in size or shape, lack of marginal abrasion, or other injuries on the surrounding skin. The most significant factor influencing the variability of the ricochet wounds was the surface the bullet deflected off before striking the body. Key Words: handgun, rifle, ricochet bullet, atypical gunshot wound (Am J Forensic Med Pathol 2016;37: 284–290)
M
ultiple factors influence the morphology of an entrance gunshot wound. Aspects intrinsic to the body include the location of entry, thickness of the skin injured, underlying bony structures, and reentry into additional body parts. Extrinsic features, such as the caliber, construction, and composition of projectiles, also affect the appearance of entrance wounds. Any factor that makes the entrance gunshot wound appear atypical adds to the difficulty a forensic pathologist may face in examining firearm injuries. One such factor that creates atypical entrance wounds is when the bullet strikes an object and deflects or ricochets off the object before striking the body. These fired bullets may become destabilized in flight after striking an object, and in low-angle impacts with an object, some projectiles can ricochet and create atypical entrance wounds. Confusion still exists in the medicolegal community regarding ricochet bullets and the interpretation of the entrance wounds they create. Previous studies extensively examined the conditions and angles of impact that favorably produce ricochets and have detailed the resulting ricocheted projectiles, but there are currently no articles published on a large series of ricochet entrance wounds involving different firearm calibers. The aim of this study is to compare and contrast typical gunshot entrance wounds created by conventional firearm calibers to entrance wounds resulting from bullets ricocheting off commonly encountered surfaces. We Manuscript received June 14, 2016; accepted September 5, 2016. From the *Department of Pathology, University of Michigan, †Wayne County Medical Examiner's Office; ‡Department of Pathology at the University of Michigan, Ann Arbor; and §Firearms and Toolmarks Identification Unit of the Michigan State Police Forensic Laboratory, Lansing, MI. The authors report no conflict of interest. Reprints: Leigh Hlavaty, MD, Wayne County Medical Examiner's Office, 1300 E. Warren Ave. Detroit, MI 48207. E-mail: [email protected]. Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved. ISSN: 0195-7910/16/3704–0284 DOI: 10.1097/PAF.0000000000000277
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anticipate the results of this study will be useful for forensic pathologists in their assessment of atypical firearm injuries and will be invaluable as a reference for their opinion in trial.
MATERIALS AND METHODS This study was conducted at the Forensic Crime Laboratory in the Detroit Public Safety Headquarters building in cooperation with the Michigan State Police. Four handgun calibers that are commonly used in our jurisdiction were selected for analysis: .22 long rifle (22LR), 9 19 mm Parabellum (9 mm), .40 Smith &Wesson (.40 S&W), and .45 Automatic Colt Pistol (.45 ACP). The 2 most frequently encountered rifle calibers in our office were the 5.56 and 7.62 mm, and these were used in the study. To reduce variability, only 2 handgun frames were used. One frame was of a .45 ACP Glock 21 which fits its native 13.9-cm barrel and slide and is able to mount an Advantage Arms 22LR conversion kit slide with a 11.43-cm barrel. The other was the frame and slide of a .40 S&W Glock 23 with its native 9.5-cm barrel. The Glock 23 slide accepts a 10.2-cm Lone Wolf conversion barrel, allowing it to chamber and fire 9-mm cartridges. The 5.56 45 mm (5.56 North Atlantic Treaty Organization [NATO]) round was fired using a Colt M4 with at 17¼-in barrel, and a Norinco MAK90 with a 16¼-in barrel fired a 7.62 39 mm (7.62 mm) cartridge. A single shooter fired all the rounds, a detective lieutenant currently assigned as the supervisor of the Firearms and Toolmarks Identification Unit with 22 years law enforcement experience and 12 years forensic science experience.
FIGURE 1. Illustration of witness panel. Am J Forensic Med Pathol • Volume 37, Number 4, December 2016
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Am J Forensic Med Pathol • Volume 37, Number 4, December 2016
Examination of Ricochet Gunshot Wounds
TABLE 1. Bullet Summary and Specifications Caliber .22 LR .22 LR 9 19 mm 9 19 mm .40 S&W .40 S&W .45 ACP .45 ACP 5.56 45 mm 7.62 39 mm
Manufacturer
Model
Bullet Type
Bullet Weight (Grains)
Average Velocity, m/s
CCl Remington Speer Speer Speer Speer Speer Speer Remington Wolf
Mini Mag Golden Lawman Gold Dot Lawman Gold Dot Lawman Gold Dot
Solid Hollow Point TMJ HP TMJ HP TMJ HP FMJ FMJ
40 36 124 124 180 180 230 230 55 122
299 287 357 347 287 297 230 242 871 709
The witness panel used throughout the experiment was a vertical piece of cardboard covered with porcine skin affixed with metal staples. Porcine skin was used as an analog for human skin, as previous research groups have shown that porcine skin shares many anatomic, physiologic, histologic, histochemical, and immunohistochemical properties as human skin.1,2 The witness panel frame was constructed from 1½-in PVC schedule 40 pipe and wood furring strips with cardboard backing to secure the porcine skin (Fig. 1). A Nikon D90 digital camera with an AF Zoom-NIKKOR 24–85 mm f/2.8-4D IF lens was used to document the morphology of the entrance gunshot wounds in the porcine skin and of the projectiles. Control shots in which the weapons were fired directly at a target (witness panel) and without intervening surface were conducted for each of the 4 handgun and 2 rifle calibers to determine the average velocity of each round and to obtain standard entrance gunshot wounds for each caliber. The target was positioned 5 yards from the muzzle of the weapon. Five rounds of each caliber and bullet type were fired through a chronograph and into the witness panel. The wounds in the witness panel were photographed, and the velocities from the chronograph were recorded. The fired projectiles, if recoverable, were also collected. Both total-metal-jacketed (TMJ) and hollow-point (HP) bullet types were used for the 9 mm, .40 S&W, and .45 ACP calibers, solid and HP bullet types were used for the 22LR, and only fullmetal-jacket (FMJ) bullets were used for the 5.56 NATO and 7.62 mm (Table 1). The control shots and the shots using concrete as the ricochet surface were performed on all the ammunition
types (solid and TMJ, HP, and FMJ). Because of the no appreciable differences in the concrete ricochet entrance gunshot wounds, the HP bullets were abandoned, and only the solid and TMJ bullets were used for the remainder of the handgun testing of the other ricochet surfaces. The Speer Gold Dot HP and the Lawman TMJ series of ammunition were used to decrease differences in the performance of the cartridges, because these 2 series of ammunition were designed to have similar velocities and internal, transitional, and external ballistics. Ricochet shots, in which the weapons were fired at reproducible shallow angles to 5 commonly encountered surfaces, were conducted for each of the calibers to obtain entrance gunshot wounds after ricochet for each caliber. The fired projectiles, if recoverable, were also collected. These ricochet shots were taken with a shooting platform placed 5 yards in front of the substrate table and the different ricochet surfaces placed onto a substrate table, which was positioned 3 f. behind the witness panel (Fig. 2). Each weapon was individually steadied using a fixed platform (Caldwell Stable Table) and a shooting stand (CTK P3 Ultimate Shooting Rest). With an inclinometer (Digi-Pas DWL-80E Mini Digital Level), the telescoping front forearm rest of the shooting stand was raised or lowered for each firearm to create a reproducible 10-degree incident angle with the ricochet impact substrates. In addition to the coarse adjustment of the front forearm rest, rotating the stabilization feet and rear weapon pad allowed finetuning of the incident angle (Fig. 3). Five rounds of each caliber were fired at each surface and into the witness panel. Ricochet impact substrates were chosen based on their frequency in the environment of our jurisdiction. Yielding surfaces
FIGURE 3. Incident angle adjustment using shooting stand and inclinometer.
FIGURE 2. Experimental setup. © 2016 Wolters Kluwer Health, Inc. All rights reserved.
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FIGURE 4. Control entrance wounds for each caliber and bullet type.
are those that are soft enough to allow a bullet to enter the surface, as opposed to those that are hard and unyielding upon impact. Frangible surfaces fracture upon impact with a projectile, as opposed to those surfaces that remain largely intact after sustaining an impact. Homogenous surfaces are those composed of the same material throughout, whereas heterogeneous surfaces consist of several layers or different substrates. We used concrete paver step-stones, made from Portland cement concrete, which is a nonhomogenous surface that is nonyielding and nonfrangible. Performance-grade asphalt concrete was also used, which is a nonhomogenous surface that is yielding and frangible. Department of transportation–approved aluminum traffic signs (0.080 in thick) were selected and are homogenous surfaces that are yielding but nonfrangible. Clay brick was used, which is considered to be homogenous, yielding, and frangible, and drywall with 2 coats of flat paint represented materials that are heterogeneous, frangible, and yielding. These surfaces were placed onto the substrate stage, which was a short table constructed from a plywood board with adjustable legs. Segments could be incrementally added to the legs to raise the surface to achieve the ricochet gunshot wounds onto the witness panel.
RESULTS Figure 4 shows representative examples of the control entrance wounds for each caliber and bullet type. All control shots
produced typical entrance wounds consisting of circular perforations with marginal abrasions. None of the control entrance wounds displayed any atypical features, such as irregularities in the wound shape or lack of marginal abrasion, or had injuries on the surrounding skin. The diameter of each entrance wound, not including the abrasion collar, was consistently smaller than the diameter of the bullet creating it (Table 2). These wounds ranged from 21.6% smaller for the 9-mm controls to 43.5% smaller for the 7.62-mm controls. There was a difference between the appearance of the TMJ entrance wounds and the HP entrance wounds in the control shots. The HP entrance wounds had a more punched-out appearance and more resembled a hole than the TMJ wounds. A bullet wipe is a gray or black fairly well-demarcated ring around an entrance bullet hole in skin or clothing that comes from the lubricant and debris on a bullet's surface and is deposited on the edges of the entrance hole. Bullet wipe was present to some degree on the margins of every handgun control shot, was more noticeable for the TMJ entrance wounds than the HP wounds, and more prevalent in the .45 ACP entrance wounds. Minimal bullet wipe was identified on the 5.56 NATO entrance wound and was absent on the 7.62 mm. We examined over 150 ricochet entrance wounds, and none had the features of a typical entrance wound. Every shot resulted in an entrance wound with at least 1 atypical feature, such as
TABLE 2. Control Bullet Caliber Versus Entrance Wound Diameter Caliber .22LR 9 19 mm .40 S&W .45 ACP 5.56 45 mm 7.62 39 mm
286
Entrance Wound Diameter
Size Difference
0.155 in 7.055 mm 0.285 in 0.328 in 3.315 mm 4.303 mm
−28.3% −21.6% −28.7% −27.9% −40.3% −43.5%
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FIGURE 5. Total metal jacket bullet tip and side views. A, Control. B, Ricochet off concrete. © 2016 Wolters Kluwer Health, Inc. All rights reserved.
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Am J Forensic Med Pathol • Volume 37, Number 4, December 2016
Examination of Ricochet Gunshot Wounds
FIGURE 6. Hollow point bullet. A, Control tip and side views. B, Ricochet off concrete tip and side views. C, Ricochet off concrete showing striations.
irregular size or shape, pseudostippling or injuries on the surrounding skin, or features mimicking an exit wound. A fair number of wounds were created by the bullet striking the target on its side for all calibers tested. There was no significant difference between the atypical features of the ricochet wounds from the different calibers studied or between the different bullet types studied. Bullet wipe was still present around most wounds, though when present was much less noticeable when compared with the control shots, and was again most noticeable with the .45 ACP entrance wounds. Examination of the fired projectiles provided insight into the orientation of the bullet upon impact as well as the type and composition of the ricochet surfaces. Concrete is a nonyielding surface, so when a bullet ricocheted off concrete it deformed and frequently flattened at its point of impact with the concrete.
FIGURE 8. Ricochet entrance wounds off brick.
Figure 5 shows both the side and nose views of .45 ACP TMJ fired control bullet and fired concrete ricochet bullet, illustrating the damage characteristically seen when a bullet ricochets off a nonyielding substrate such as concrete. Figure 6 shows both the side and nose views of a .45 ACP HP fired control bullet and a fired concrete ricochet bullet, demonstrating how the HP failed to expand and created a deformed projectile similar to the TMJ concrete bullet in Figure 5. Figure 6C shows the characteristic roughened or striated appearance of the flattened surface of the projectile after striking concrete. Representative examples of the ricochet entrance wounds for concrete from all calibers and bullet types per caliber are shown in
FIGURE 7. Ricochet entrance wounds off concrete. © 2016 Wolters Kluwer Health, Inc. All rights reserved.
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Figure 7. All of the wounds were atypical, and because concrete did not fragment, no appreciable pseudostippling or additional injuries on the surrounding skin were apparent. Hollow-point bullets failed to expand when the bullets struck the concrete and resulted in flattened deformed projectiles showing similarities to the TMJ ricochet bullets. No appreciable differences between the ricochet wounds created by the solid and TMJ bullets, and those created by the HP bullets could be seen, thus the decision was made to test the other four ricochet surfaces using only the solid and TMJ bullets. Representative examples of the ricochet entrance wounds for brick for all calibers are shown in Figure 8. All wounds showed atypical appearances, and in approximately half of the wounds, the bullet struck the witness panel on its side. Brick, being a frangible surface, breaks up upon impact with the bullet, thus increasing the propensity of having pseudostippling from the resulting brick dust on the skin surrounding the entrance wounds. Figure 9 is a composite of the pseudostippling from this dust associated with bullets ricocheting off brick. Variation in the size, shape, and spacing of the stippling pattern from brick dust may be present, but the dust can also be fine and homogenous and simulate true gunpowder stippling as seen in Figure 9A. The most pseudostippling was noted with the 5.56 FMJ rounds. Representative examples of the ricochet entrance wounds from asphalt for the calibers are shown in Figure 10. All of the wounds were atypical. Asphalt is also a frangible, so pseudostippling from the asphalt dust can occur on the skin surrounding these entrance wounds. Figure 11 is a composite of the pseudostippling from this dust and can have an appearance mimicking true gunpowder stippling. The most pseudostippling was again noted with the 5.56 FMJ rifle rounds. Asphalt is also a heterogeneous and yielding material, and it created greater variation in the shape and appearance of the entrance wounds than any of the other surfaces. There was at least 1 wound for each of the handgun calibers tested that mimicked a typical exit wound by either being a slit-like defect or having nonabraded margins that could be re-approximated (Fig. 12). The wounds created by both rifle rounds showed extreme variability.
FIGURE 10. Ricochet entrance wounds off asphalt.
Representative examples of the ricochet entrance wounds for the aluminum signs for all calibers are shown in Figure 13. As with all of the previous surfaces, all of the wounds were atypical. Aluminum signs are yielding though nonfrangible, so the wounds showed little pseudostippling. Drywall is a very yielding surface, so much so that we could not find a reproducible angle at which any bullet would ricochet off the surface and onto the witness panel. All bullets passed into or through the drywall and did not strike the porcine skin.
DISCUSSION
FIGURE 9. Pseudostippling from brick dust. A, .40 TMJ. B, .45 TMJ. C, .45 TMJ. D, 5.56 FMJ. E, 7.62 FMJ. F, 7.62 FMJ.
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The appearance of a gunshot wound on the body is dependent on the type of firearm, the type of ammunition, the location of the wound on the body, and the path traversed by the bullet prior to contact with the body. Entire books have been devoted to the interpretation of these wounds.3 A typical gunshot entrance wound is created by a bullet striking the body nose first. An atypical gunshot wound results when the bullet strikes the skin at an angle due destabilization of its course prior to entering the body. Ricochet is 1 form of destabilization and can be defined as the flight of a bullet and/or its major fragments after deflection off, rather than penetration or perforation through, a surface or an object.4 The interpretation of these atypical wounds and deformed projectiles requires experience and expertise on the part of the forensic pathologist, as well as consultation with a firearms and ballistics expert, and careful scene investigation. All control shots for the 4 common handgun calibers, 2 rifle calibers, and different bullet types tested produced typical entrance wounds consisting of punched out holes with a surrounding rim of abrasion. The diameter of each entrance wound was smaller than the diameter of the bullet creating it, even without the underlying soft tissue. No correlation could be made between the caliber of the bullet and the size of the wound. The morphology of the entrance wounds created by HP bullets showed differences and similarities to those created by the TMJ bullets in the control shots and ricochet shots, respectfully. © 2016 Wolters Kluwer Health, Inc. All rights reserved.
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Am J Forensic Med Pathol • Volume 37, Number 4, December 2016
Examination of Ricochet Gunshot Wounds
FIGURE 11. Pseudostippling from asphalt dust.
In the control shots, the HP entrance wounds possessed a more distinct, punched-out appearance and more closely resembled a symmetrical hole than the TMJ wounds. With the ricochet shots, the hollow of the HP bullet collapsed upon impact with the ricochet surface and would be prevented from expanding further. The projectile thus mirrored the deformation and flattening experience by a TMJ bullet and created similar atypical wounds, a phenomenon that has been previously described.5 Bullet wipe can be seen around holes made from both lead and jacketed handgun bullets. Bullet wipe was present on the edges of the wounds for all handgun control shots and was most noticeable on the TMJ wounds regardless of caliber and on the .45 ACP wounds regardless of bullet type. The edges of the ricochet wounds also displayed bullet wipe, although to a much less extent than the control wounds, and were again most noticeable on the .45 ACP ricochet wounds. This inconsistent and decreased bullet wipe around ricochet wounds makes sense, as much of the residue on the surface of the bullet producing the bullet wipe is likely deposited on the ricochet surface itself.4 The wounds created by the 2 rifles exhibited minimal-to-no bullet wipe, which may reflect the more complete combustion of gunpowder through the 2 rifles' longer barrels. All the ricochet wounds for the all calibers and different bullet types we tested produced atypical entrance wounds were either irregular size or shape, lacked a marginal abrasion, or had injuries on the surrounding skin. This is in contrast to previous studies describing ricochet entrance wounds displaying typical gunshot entrance wound appearance.5 There was no significant difference between the atypical features of the ricochet wounds from the different calibers studied, or between the different bullet types studied as the HP bullets failed to expand and acted like the TMJ bullets. A number of the wounds were created by the bullet striking the target on its side for all calibers; however, there was no
prevalence of D-shaped entrance wounds, as described in some previous studies.6,7 No correlation could be made between the caliber of the bullet and the size of the wound for any of the ricochet shots, similar to our control shots. This is in contrast to some of the previous articles on ricochet wounds describing wounds usually larger than the projectile.8 The most significant factor in interpreting ricochet wounds was the surface the bullet deflected off before striking the body. Bullets striking a nonyielding surface, such as concrete, flatten at their point of impact with the surface. Examination of the deformed projectile from a concrete ricochet shot can show a roughened or striated appearance to the flattened surface. This has been previously described, along with a smooth or polished mirror appearance to the flattened surface on a deformed projectile ricocheting off a nonyielding surface, such as granite.4 Other studies described a deformed projectile with a smooth flattened surface recovered from ricochet shots without correlation to the ricochet surface itself.8,9 Nonyielding surfaces, such as concrete, resist fragmentation upon impact by a bullet, and little to no pseudostippling or other injuries are present on the skin surrounding the atypical entrance wound on the body. Frangible surfaces, such as brick or asphalt, readily fragments or breaks up upon impact with a bullet. The fragments and dust from the surface can strike the skin surrounding the atypical entrance wound created by the ricochet bullet and result in pseudostippling. Even though careful examination of the pseudostippling from brick and asphalt in our cases revealed some irregularities in the size and spacing of the material and allowed distinction from true gunpowder stippling, examples from brick and especially dark colored bricks may be difficult to interpret with the naked eye. This is perhaps in contrast to previous observations indicating the ease in differentiating evidence of close range fire from pseudostippling produced from frangible surfaces.5
FIGURE 12. Exit wound mimics from ricochet off asphalt. © 2016 Wolters Kluwer Health, Inc. All rights reserved.
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LIMITATIONS We did not vary the incident angles between the bullets and ricochet surfaces, and the incident angle can affect the shape of the entrance gunshot wound and the deformation of the projectiles and ricochet surfaces. We did not vary the distance of the weapon to the ricochet surface or the distance of the ricochet surface to the witness panel, and it is possible that in doing so one can get a ricochet bullet to strike the witness panel nose first and create a typical entrance gunshot wound. Our study used a witness panel that was made of porcine skin stapled to a cardboard surface. The cardboard panel did not have the same elastic qualities of human soft tissue and thus could have affected the appearance of the entrance wound. REFERENCES 1. Debeer S, Le Luduec JB, Kaiserlian D, et al Comparative histology and immunohistochemistry of porcine versus human skin. Eur J Dermatol. 2013;23(4):456–466. 2. Haag M, Haag L. Skin perforation and skin simulants. AFTE Journal. 2002; 34(3):268–286. 3. Dimaio V. Gunshot Wounds: Practical Aspects of Firearms, Ballistics, and Forensic Techniques. Third ed. Boca Raton: CRC Press; 2015.
FIGURE 13. Ricochet entrance wounds off aluminum.
Heterogeneous surfaces, such as asphalt, are made of several layers of different substrates and bitumen that can fragment upon impact with a bullet. These irregular pieces produce pseudostippling on the skin surrounding the entrance wound similar to those seen with frangible surfaces. This pseudostippling was most appreciated with the rifle rounds. In addition, the variability in the composition of the surface resulted in entrance wounds with the greatest variability in size and shape. Asphalt ricochets also had the highest number of atypical handgun entrance wounds mimicking exit wounds by being either slit-like or lacking a marginal abrasion.
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4. Haag M. Projectile Ricochet and Deflection. In: Shooting Incident Reconstruction. San Diego, CA: Elsevier; 2011:143–174. 5. Haag L. Wound Production by Ricocheted and Destabilized Bullets. Am J Forensic Med Pathol. 2007;28(1):4–12. 6. Denton JS, Segovia A, Filkins JA. Practical pathology of gunshot wounds. Arch Pathol Lab Med. 2006;130(9):1283–1289. 7. Donoghue ER, Kalelkar MB, Richmond JM, et al Atypical gunshot wounds of entrance: an empirical study. J Forensic Sci. 1984;29(2):379–388. 8. Burke T, Rowe W. Bullet ricochet: a comprehensive review. J Forensic Sci. 1992;37(5):1254–1260. 9. Molina D, Rulon JJ, Wallace II. The atypical entrance wound: differential diagnosis and discussion of an unusual cause. Am J Forensic Med Pathol. 2012;33(3):250–252.
© 2016 Wolters Kluwer Health, Inc. All rights reserved.
Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.
Examination of Ricochet Gunshot Wounds From Commonly Encountered Surfaces Leigh Hlavaty, MD,*† Sarah Avedschmidt, MD,‡ Kelly Root,*† Jeffrey Amley,§ and LokMan Sung, MD*† Abstract: Proper interpretation of gunshot wounds is vital for the forensic pathologist and requires experience and expertise, as well as consultation with a firearms and ballistics expert and careful scene investigation in cases of atypical gunshot wounds. This study is the first large-series examining ricochet gunshot wounds involving different firearm calibers. Typical gunshot wounds created from 4 handgun calibers (22 Long Rifle, 9 19 mm Parabellum, .40 Smith &Wesson, and .45 Automatic Colt Pistol) and 2 rifle calibers (5.56 and 7.62 mm) were compared with wounds caused by bullets of those same calibers ricocheting off commonly encountered surfaces (concrete, asphalt, aluminum traffic signs, clay brick, and dry wall). Porcine skin, a human skin analog, attached to sheets of cardboard serviced as witness panels for capturing the entrance wounds. Examination of over 150 handgun and rifle entrance wounds established that every caliber and every ricochet surface resulted in atypical features, including irregularity in size or shape, lack of marginal abrasion, or other injuries on the surrounding skin. The most significant factor influencing the variability of the ricochet wounds was the surface the bullet deflected off before striking the body. Key Words: handgun, rifle, ricochet bullet, atypical gunshot wound (Am J Forensic Med Pathol 2016;37: 284–290)
M
ultiple factors influence the morphology of an entrance gunshot wound. Aspects intrinsic to the body include the location of entry, thickness of the skin injured, underlying bony structures, and reentry into additional body parts. Extrinsic features, such as the caliber, construction, and composition of projectiles, also affect the appearance of entrance wounds. Any factor that makes the entrance gunshot wound appear atypical adds to the difficulty a forensic pathologist may face in examining firearm injuries. One such factor that creates atypical entrance wounds is when the bullet strikes an object and deflects or ricochets off the object before striking the body. These fired bullets may become destabilized in flight after striking an object, and in low-angle impacts with an object, some projectiles can ricochet and create atypical entrance wounds. Confusion still exists in the medicolegal community regarding ricochet bullets and the interpretation of the entrance wounds they create. Previous studies extensively examined the conditions and angles of impact that favorably produce ricochets and have detailed the resulting ricocheted projectiles, but there are currently no articles published on a large series of ricochet entrance wounds involving different firearm calibers. The aim of this study is to compare and contrast typical gunshot entrance wounds created by conventional firearm calibers to entrance wounds resulting from bullets ricocheting off commonly encountered surfaces. We Manuscript received June 14, 2016; accepted September 5, 2016. From the *Department of Pathology, University of Michigan, †Wayne County Medical Examiner's Office; ‡Department of Pathology at the University of Michigan, Ann Arbor; and §Firearms and Toolmarks Identification Unit of the Michigan State Police Forensic Laboratory, Lansing, MI. The authors report no conflict of interest. Reprints: Leigh Hlavaty, MD, Wayne County Medical Examiner's Office, 1300 E. Warren Ave. Detroit, MI 48207. E-mail: [email protected]. Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved. ISSN: 0195-7910/16/3704–0284 DOI: 10.1097/PAF.0000000000000277
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anticipate the results of this study will be useful for forensic pathologists in their assessment of atypical firearm injuries and will be invaluable as a reference for their opinion in trial.
MATERIALS AND METHODS This study was conducted at the Forensic Crime Laboratory in the Detroit Public Safety Headquarters building in cooperation with the Michigan State Police. Four handgun calibers that are commonly used in our jurisdiction were selected for analysis: .22 long rifle (22LR), 9 19 mm Parabellum (9 mm), .40 Smith &Wesson (.40 S&W), and .45 Automatic Colt Pistol (.45 ACP). The 2 most frequently encountered rifle calibers in our office were the 5.56 and 7.62 mm, and these were used in the study. To reduce variability, only 2 handgun frames were used. One frame was of a .45 ACP Glock 21 which fits its native 13.9-cm barrel and slide and is able to mount an Advantage Arms 22LR conversion kit slide with a 11.43-cm barrel. The other was the frame and slide of a .40 S&W Glock 23 with its native 9.5-cm barrel. The Glock 23 slide accepts a 10.2-cm Lone Wolf conversion barrel, allowing it to chamber and fire 9-mm cartridges. The 5.56 45 mm (5.56 North Atlantic Treaty Organization [NATO]) round was fired using a Colt M4 with at 17¼-in barrel, and a Norinco MAK90 with a 16¼-in barrel fired a 7.62 39 mm (7.62 mm) cartridge. A single shooter fired all the rounds, a detective lieutenant currently assigned as the supervisor of the Firearms and Toolmarks Identification Unit with 22 years law enforcement experience and 12 years forensic science experience.
FIGURE 1. Illustration of witness panel. Am J Forensic Med Pathol • Volume 37, Number 4, December 2016
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Am J Forensic Med Pathol • Volume 37, Number 4, December 2016
Examination of Ricochet Gunshot Wounds
TABLE 1. Bullet Summary and Specifications Caliber .22 LR .22 LR 9 19 mm 9 19 mm .40 S&W .40 S&W .45 ACP .45 ACP 5.56 45 mm 7.62 39 mm
Manufacturer
Model
Bullet Type
Bullet Weight (Grains)
Average Velocity, m/s
CCl Remington Speer Speer Speer Speer Speer Speer Remington Wolf
Mini Mag Golden Lawman Gold Dot Lawman Gold Dot Lawman Gold Dot
Solid Hollow Point TMJ HP TMJ HP TMJ HP FMJ FMJ
40 36 124 124 180 180 230 230 55 122
299 287 357 347 287 297 230 242 871 709
The witness panel used throughout the experiment was a vertical piece of cardboard covered with porcine skin affixed with metal staples. Porcine skin was used as an analog for human skin, as previous research groups have shown that porcine skin shares many anatomic, physiologic, histologic, histochemical, and immunohistochemical properties as human skin.1,2 The witness panel frame was constructed from 1½-in PVC schedule 40 pipe and wood furring strips with cardboard backing to secure the porcine skin (Fig. 1). A Nikon D90 digital camera with an AF Zoom-NIKKOR 24–85 mm f/2.8-4D IF lens was used to document the morphology of the entrance gunshot wounds in the porcine skin and of the projectiles. Control shots in which the weapons were fired directly at a target (witness panel) and without intervening surface were conducted for each of the 4 handgun and 2 rifle calibers to determine the average velocity of each round and to obtain standard entrance gunshot wounds for each caliber. The target was positioned 5 yards from the muzzle of the weapon. Five rounds of each caliber and bullet type were fired through a chronograph and into the witness panel. The wounds in the witness panel were photographed, and the velocities from the chronograph were recorded. The fired projectiles, if recoverable, were also collected. Both total-metal-jacketed (TMJ) and hollow-point (HP) bullet types were used for the 9 mm, .40 S&W, and .45 ACP calibers, solid and HP bullet types were used for the 22LR, and only fullmetal-jacket (FMJ) bullets were used for the 5.56 NATO and 7.62 mm (Table 1). The control shots and the shots using concrete as the ricochet surface were performed on all the ammunition
types (solid and TMJ, HP, and FMJ). Because of the no appreciable differences in the concrete ricochet entrance gunshot wounds, the HP bullets were abandoned, and only the solid and TMJ bullets were used for the remainder of the handgun testing of the other ricochet surfaces. The Speer Gold Dot HP and the Lawman TMJ series of ammunition were used to decrease differences in the performance of the cartridges, because these 2 series of ammunition were designed to have similar velocities and internal, transitional, and external ballistics. Ricochet shots, in which the weapons were fired at reproducible shallow angles to 5 commonly encountered surfaces, were conducted for each of the calibers to obtain entrance gunshot wounds after ricochet for each caliber. The fired projectiles, if recoverable, were also collected. These ricochet shots were taken with a shooting platform placed 5 yards in front of the substrate table and the different ricochet surfaces placed onto a substrate table, which was positioned 3 f. behind the witness panel (Fig. 2). Each weapon was individually steadied using a fixed platform (Caldwell Stable Table) and a shooting stand (CTK P3 Ultimate Shooting Rest). With an inclinometer (Digi-Pas DWL-80E Mini Digital Level), the telescoping front forearm rest of the shooting stand was raised or lowered for each firearm to create a reproducible 10-degree incident angle with the ricochet impact substrates. In addition to the coarse adjustment of the front forearm rest, rotating the stabilization feet and rear weapon pad allowed finetuning of the incident angle (Fig. 3). Five rounds of each caliber were fired at each surface and into the witness panel. Ricochet impact substrates were chosen based on their frequency in the environment of our jurisdiction. Yielding surfaces
FIGURE 3. Incident angle adjustment using shooting stand and inclinometer.
FIGURE 2. Experimental setup. © 2016 Wolters Kluwer Health, Inc. All rights reserved.
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FIGURE 4. Control entrance wounds for each caliber and bullet type.
are those that are soft enough to allow a bullet to enter the surface, as opposed to those that are hard and unyielding upon impact. Frangible surfaces fracture upon impact with a projectile, as opposed to those surfaces that remain largely intact after sustaining an impact. Homogenous surfaces are those composed of the same material throughout, whereas heterogeneous surfaces consist of several layers or different substrates. We used concrete paver step-stones, made from Portland cement concrete, which is a nonhomogenous surface that is nonyielding and nonfrangible. Performance-grade asphalt concrete was also used, which is a nonhomogenous surface that is yielding and frangible. Department of transportation–approved aluminum traffic signs (0.080 in thick) were selected and are homogenous surfaces that are yielding but nonfrangible. Clay brick was used, which is considered to be homogenous, yielding, and frangible, and drywall with 2 coats of flat paint represented materials that are heterogeneous, frangible, and yielding. These surfaces were placed onto the substrate stage, which was a short table constructed from a plywood board with adjustable legs. Segments could be incrementally added to the legs to raise the surface to achieve the ricochet gunshot wounds onto the witness panel.
RESULTS Figure 4 shows representative examples of the control entrance wounds for each caliber and bullet type. All control shots
produced typical entrance wounds consisting of circular perforations with marginal abrasions. None of the control entrance wounds displayed any atypical features, such as irregularities in the wound shape or lack of marginal abrasion, or had injuries on the surrounding skin. The diameter of each entrance wound, not including the abrasion collar, was consistently smaller than the diameter of the bullet creating it (Table 2). These wounds ranged from 21.6% smaller for the 9-mm controls to 43.5% smaller for the 7.62-mm controls. There was a difference between the appearance of the TMJ entrance wounds and the HP entrance wounds in the control shots. The HP entrance wounds had a more punched-out appearance and more resembled a hole than the TMJ wounds. A bullet wipe is a gray or black fairly well-demarcated ring around an entrance bullet hole in skin or clothing that comes from the lubricant and debris on a bullet's surface and is deposited on the edges of the entrance hole. Bullet wipe was present to some degree on the margins of every handgun control shot, was more noticeable for the TMJ entrance wounds than the HP wounds, and more prevalent in the .45 ACP entrance wounds. Minimal bullet wipe was identified on the 5.56 NATO entrance wound and was absent on the 7.62 mm. We examined over 150 ricochet entrance wounds, and none had the features of a typical entrance wound. Every shot resulted in an entrance wound with at least 1 atypical feature, such as
TABLE 2. Control Bullet Caliber Versus Entrance Wound Diameter Caliber .22LR 9 19 mm .40 S&W .45 ACP 5.56 45 mm 7.62 39 mm
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Entrance Wound Diameter
Size Difference
0.155 in 7.055 mm 0.285 in 0.328 in 3.315 mm 4.303 mm
−28.3% −21.6% −28.7% −27.9% −40.3% −43.5%
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FIGURE 5. Total metal jacket bullet tip and side views. A, Control. B, Ricochet off concrete. © 2016 Wolters Kluwer Health, Inc. All rights reserved.
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Examination of Ricochet Gunshot Wounds
FIGURE 6. Hollow point bullet. A, Control tip and side views. B, Ricochet off concrete tip and side views. C, Ricochet off concrete showing striations.
irregular size or shape, pseudostippling or injuries on the surrounding skin, or features mimicking an exit wound. A fair number of wounds were created by the bullet striking the target on its side for all calibers tested. There was no significant difference between the atypical features of the ricochet wounds from the different calibers studied or between the different bullet types studied. Bullet wipe was still present around most wounds, though when present was much less noticeable when compared with the control shots, and was again most noticeable with the .45 ACP entrance wounds. Examination of the fired projectiles provided insight into the orientation of the bullet upon impact as well as the type and composition of the ricochet surfaces. Concrete is a nonyielding surface, so when a bullet ricocheted off concrete it deformed and frequently flattened at its point of impact with the concrete.
FIGURE 8. Ricochet entrance wounds off brick.
Figure 5 shows both the side and nose views of .45 ACP TMJ fired control bullet and fired concrete ricochet bullet, illustrating the damage characteristically seen when a bullet ricochets off a nonyielding substrate such as concrete. Figure 6 shows both the side and nose views of a .45 ACP HP fired control bullet and a fired concrete ricochet bullet, demonstrating how the HP failed to expand and created a deformed projectile similar to the TMJ concrete bullet in Figure 5. Figure 6C shows the characteristic roughened or striated appearance of the flattened surface of the projectile after striking concrete. Representative examples of the ricochet entrance wounds for concrete from all calibers and bullet types per caliber are shown in
FIGURE 7. Ricochet entrance wounds off concrete. © 2016 Wolters Kluwer Health, Inc. All rights reserved.
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Figure 7. All of the wounds were atypical, and because concrete did not fragment, no appreciable pseudostippling or additional injuries on the surrounding skin were apparent. Hollow-point bullets failed to expand when the bullets struck the concrete and resulted in flattened deformed projectiles showing similarities to the TMJ ricochet bullets. No appreciable differences between the ricochet wounds created by the solid and TMJ bullets, and those created by the HP bullets could be seen, thus the decision was made to test the other four ricochet surfaces using only the solid and TMJ bullets. Representative examples of the ricochet entrance wounds for brick for all calibers are shown in Figure 8. All wounds showed atypical appearances, and in approximately half of the wounds, the bullet struck the witness panel on its side. Brick, being a frangible surface, breaks up upon impact with the bullet, thus increasing the propensity of having pseudostippling from the resulting brick dust on the skin surrounding the entrance wounds. Figure 9 is a composite of the pseudostippling from this dust associated with bullets ricocheting off brick. Variation in the size, shape, and spacing of the stippling pattern from brick dust may be present, but the dust can also be fine and homogenous and simulate true gunpowder stippling as seen in Figure 9A. The most pseudostippling was noted with the 5.56 FMJ rounds. Representative examples of the ricochet entrance wounds from asphalt for the calibers are shown in Figure 10. All of the wounds were atypical. Asphalt is also a frangible, so pseudostippling from the asphalt dust can occur on the skin surrounding these entrance wounds. Figure 11 is a composite of the pseudostippling from this dust and can have an appearance mimicking true gunpowder stippling. The most pseudostippling was again noted with the 5.56 FMJ rifle rounds. Asphalt is also a heterogeneous and yielding material, and it created greater variation in the shape and appearance of the entrance wounds than any of the other surfaces. There was at least 1 wound for each of the handgun calibers tested that mimicked a typical exit wound by either being a slit-like defect or having nonabraded margins that could be re-approximated (Fig. 12). The wounds created by both rifle rounds showed extreme variability.
FIGURE 10. Ricochet entrance wounds off asphalt.
Representative examples of the ricochet entrance wounds for the aluminum signs for all calibers are shown in Figure 13. As with all of the previous surfaces, all of the wounds were atypical. Aluminum signs are yielding though nonfrangible, so the wounds showed little pseudostippling. Drywall is a very yielding surface, so much so that we could not find a reproducible angle at which any bullet would ricochet off the surface and onto the witness panel. All bullets passed into or through the drywall and did not strike the porcine skin.
DISCUSSION
FIGURE 9. Pseudostippling from brick dust. A, .40 TMJ. B, .45 TMJ. C, .45 TMJ. D, 5.56 FMJ. E, 7.62 FMJ. F, 7.62 FMJ.
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The appearance of a gunshot wound on the body is dependent on the type of firearm, the type of ammunition, the location of the wound on the body, and the path traversed by the bullet prior to contact with the body. Entire books have been devoted to the interpretation of these wounds.3 A typical gunshot entrance wound is created by a bullet striking the body nose first. An atypical gunshot wound results when the bullet strikes the skin at an angle due destabilization of its course prior to entering the body. Ricochet is 1 form of destabilization and can be defined as the flight of a bullet and/or its major fragments after deflection off, rather than penetration or perforation through, a surface or an object.4 The interpretation of these atypical wounds and deformed projectiles requires experience and expertise on the part of the forensic pathologist, as well as consultation with a firearms and ballistics expert, and careful scene investigation. All control shots for the 4 common handgun calibers, 2 rifle calibers, and different bullet types tested produced typical entrance wounds consisting of punched out holes with a surrounding rim of abrasion. The diameter of each entrance wound was smaller than the diameter of the bullet creating it, even without the underlying soft tissue. No correlation could be made between the caliber of the bullet and the size of the wound. The morphology of the entrance wounds created by HP bullets showed differences and similarities to those created by the TMJ bullets in the control shots and ricochet shots, respectfully. © 2016 Wolters Kluwer Health, Inc. All rights reserved.
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Examination of Ricochet Gunshot Wounds
FIGURE 11. Pseudostippling from asphalt dust.
In the control shots, the HP entrance wounds possessed a more distinct, punched-out appearance and more closely resembled a symmetrical hole than the TMJ wounds. With the ricochet shots, the hollow of the HP bullet collapsed upon impact with the ricochet surface and would be prevented from expanding further. The projectile thus mirrored the deformation and flattening experience by a TMJ bullet and created similar atypical wounds, a phenomenon that has been previously described.5 Bullet wipe can be seen around holes made from both lead and jacketed handgun bullets. Bullet wipe was present on the edges of the wounds for all handgun control shots and was most noticeable on the TMJ wounds regardless of caliber and on the .45 ACP wounds regardless of bullet type. The edges of the ricochet wounds also displayed bullet wipe, although to a much less extent than the control wounds, and were again most noticeable on the .45 ACP ricochet wounds. This inconsistent and decreased bullet wipe around ricochet wounds makes sense, as much of the residue on the surface of the bullet producing the bullet wipe is likely deposited on the ricochet surface itself.4 The wounds created by the 2 rifles exhibited minimal-to-no bullet wipe, which may reflect the more complete combustion of gunpowder through the 2 rifles' longer barrels. All the ricochet wounds for the all calibers and different bullet types we tested produced atypical entrance wounds were either irregular size or shape, lacked a marginal abrasion, or had injuries on the surrounding skin. This is in contrast to previous studies describing ricochet entrance wounds displaying typical gunshot entrance wound appearance.5 There was no significant difference between the atypical features of the ricochet wounds from the different calibers studied, or between the different bullet types studied as the HP bullets failed to expand and acted like the TMJ bullets. A number of the wounds were created by the bullet striking the target on its side for all calibers; however, there was no
prevalence of D-shaped entrance wounds, as described in some previous studies.6,7 No correlation could be made between the caliber of the bullet and the size of the wound for any of the ricochet shots, similar to our control shots. This is in contrast to some of the previous articles on ricochet wounds describing wounds usually larger than the projectile.8 The most significant factor in interpreting ricochet wounds was the surface the bullet deflected off before striking the body. Bullets striking a nonyielding surface, such as concrete, flatten at their point of impact with the surface. Examination of the deformed projectile from a concrete ricochet shot can show a roughened or striated appearance to the flattened surface. This has been previously described, along with a smooth or polished mirror appearance to the flattened surface on a deformed projectile ricocheting off a nonyielding surface, such as granite.4 Other studies described a deformed projectile with a smooth flattened surface recovered from ricochet shots without correlation to the ricochet surface itself.8,9 Nonyielding surfaces, such as concrete, resist fragmentation upon impact by a bullet, and little to no pseudostippling or other injuries are present on the skin surrounding the atypical entrance wound on the body. Frangible surfaces, such as brick or asphalt, readily fragments or breaks up upon impact with a bullet. The fragments and dust from the surface can strike the skin surrounding the atypical entrance wound created by the ricochet bullet and result in pseudostippling. Even though careful examination of the pseudostippling from brick and asphalt in our cases revealed some irregularities in the size and spacing of the material and allowed distinction from true gunpowder stippling, examples from brick and especially dark colored bricks may be difficult to interpret with the naked eye. This is perhaps in contrast to previous observations indicating the ease in differentiating evidence of close range fire from pseudostippling produced from frangible surfaces.5
FIGURE 12. Exit wound mimics from ricochet off asphalt. © 2016 Wolters Kluwer Health, Inc. All rights reserved.
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LIMITATIONS We did not vary the incident angles between the bullets and ricochet surfaces, and the incident angle can affect the shape of the entrance gunshot wound and the deformation of the projectiles and ricochet surfaces. We did not vary the distance of the weapon to the ricochet surface or the distance of the ricochet surface to the witness panel, and it is possible that in doing so one can get a ricochet bullet to strike the witness panel nose first and create a typical entrance gunshot wound. Our study used a witness panel that was made of porcine skin stapled to a cardboard surface. The cardboard panel did not have the same elastic qualities of human soft tissue and thus could have affected the appearance of the entrance wound. REFERENCES 1. Debeer S, Le Luduec JB, Kaiserlian D, et al Comparative histology and immunohistochemistry of porcine versus human skin. Eur J Dermatol. 2013;23(4):456–466. 2. Haag M, Haag L. Skin perforation and skin simulants. AFTE Journal. 2002; 34(3):268–286. 3. Dimaio V. Gunshot Wounds: Practical Aspects of Firearms, Ballistics, and Forensic Techniques. Third ed. Boca Raton: CRC Press; 2015.
FIGURE 13. Ricochet entrance wounds off aluminum.
Heterogeneous surfaces, such as asphalt, are made of several layers of different substrates and bitumen that can fragment upon impact with a bullet. These irregular pieces produce pseudostippling on the skin surrounding the entrance wound similar to those seen with frangible surfaces. This pseudostippling was most appreciated with the rifle rounds. In addition, the variability in the composition of the surface resulted in entrance wounds with the greatest variability in size and shape. Asphalt ricochets also had the highest number of atypical handgun entrance wounds mimicking exit wounds by being either slit-like or lacking a marginal abrasion.
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4. Haag M. Projectile Ricochet and Deflection. In: Shooting Incident Reconstruction. San Diego, CA: Elsevier; 2011:143–174. 5. Haag L. Wound Production by Ricocheted and Destabilized Bullets. Am J Forensic Med Pathol. 2007;28(1):4–12. 6. Denton JS, Segovia A, Filkins JA. Practical pathology of gunshot wounds. Arch Pathol Lab Med. 2006;130(9):1283–1289. 7. Donoghue ER, Kalelkar MB, Richmond JM, et al Atypical gunshot wounds of entrance: an empirical study. J Forensic Sci. 1984;29(2):379–388. 8. Burke T, Rowe W. Bullet ricochet: a comprehensive review. J Forensic Sci. 1992;37(5):1254–1260. 9. Molina D, Rulon JJ, Wallace II. The atypical entrance wound: differential diagnosis and discussion of an unusual cause. Am J Forensic Med Pathol. 2012;33(3):250–252.
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