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Emergency Medicine Atlas > Part 2. Specialty Areas > Chapter 17. Forensic Medicine >

Gunshot Wounds

Associated Clinical Features

Gunshot injuries are classified as either entrance or exit wounds. Atypical wounds (grazing) may also be present. Physical findings in and around these wounds may offer evidence as to the actual mechanism, supporting or refuting the initial history given to the provider. As these findings may be transient, the emergency physician must be diligent in recognizing and documenting them at the time of presentation.

Entrance Wounds

Gunshot wounds of entrance are divided into four categories based on their range of fire: distant, intermediate, close, and contact. Range-of-fire is the distance from the gun's muzzle to the victim.

The size of the entrance wound bears no relation to the caliber of the inflicting bullet. Entrance wounds over elastic tissue will contract around the tissue defect and have a diameter much less than the caliber of the bullet.

Distant Wounds: The distant wound is inflicted from a range sufficiently distant that the bullet is the only projectile expelled from the muzzle that reaches the skin. There is no tattooing or soot deposition associated with a distant entrance wound. As the bullet penetrates the skin, friction between it and the epithelium results in the creation of an "abrasion collar" (Fig. 17.1). The width of the abrasion collar will vary with the angle of impact. Most entrance wounds will have an abrasion collar; however, gunshot wounds to the palms and soles are exceptions—there entrance wounds appear slit-like.

Intermediate-Range Wounds: Tattooing is pathognomonic for an intermediate-range gunshot wound and presents as punctate abrasions from contact with partially burned or unburned grains of gunpowder (Fig. 17.2). This tattooing cannot be wiped away. Clothing and hair, as intermediate objects, may prevent the gunpowder grains from making contact with the skin. Tattooing can, but rarely does, occur on the palms and soles owing to the thickness of their epithelium.

Figure 17.1

Distant Gunshot Wound The elliptical abrasion collars associated with these gunshot wounds of entrance indicate that the projectile passed from right to left. The range of fire is classified as distant or indeterminate based on the lack of carbonaceous material or gunpowder tattooing. (Courtesy of William S. Smock, MD.)

Figure 17.2

Intermediate-Range Gunshot Wound Punctate abrasions present on the forehead are the result of impact with unburned or partially burned gunpowder. This phenomenon is termed tattooing. Tattooing is pathognomonic for intermediate-range gunshot wounds. (Courtesy of William S. Smock, MD.)

Tattooing has been reported with a range of fire as close as 1 cm and as far away as 4 ft. The density of the abrasions and the associated pattern will depend on the barrel length, muzzle-to-skin distance, type of gunpowder (ball, flattened ball, or flake), presence of intermediate objects, and caliber of the weapon. Spherical powder travels farther and has greater penetration than flattened ball or flake powder.

Close-Range (Near Contact) Wounds: "Close range" is defined as the maximum range at which soot is deposited on the wound or clothing (Fig. 17.3) and typically is a muzzle-to-victim distance of 6 in. or less. On rare occasions, however, soot has been found on victims as far as 12 in. from the offending weapon. The concentration of soot will vary inversely with the muzzle-to-victim distance and its appearance will be affected by the type of gunpowder and ammunition used, the barrel length, the caliber, and the type of weapon.

Contact Wounds: A contact wound occurs when the barrel or muzzle is in contact with the skin or clothing as the weapon is discharged. Contact wounds can be described as tight, where the muzzle is pushed hard against the skin, or loose, where the muzzle is incompletely or loosely in contact with the skin or clothing. Wounds sustained from tight contact with the barrel can vary in appearance from a small hole with seared, blackened edges (from the discharge of hot gases and an actual flame) (Fig. 17.4), to a gaping, stellate wound (from the expansion of the skin from gases). Large stellate wounds are often misinterpreted as exit wounds based solely upon their size and without adequate examination of the wound.

Figure 17.3

Near-Contact Gunshot Wound The deposition of carbonaceous material or soot is seen on a T-shirt from a close-range gunshot wound. Clothing should be collected and placed in separate paper bags for transport to the crime laboratory. (Courtesy of William S. Smock, MD.)

Figure 17.4

Contact Gunshot Wound A contact gunshot wound from a 22-caliber handgun. (Courtesy of William S. Smock, MD.)

In a tight contact wound, all materials—the bullet, gases, soot, incompletely combusted gunpowder, and metal fragments—are driven into the wound. If the wound is over thin or bony tissue, the hot gases will cause the skin to expand to such an extent that it stretches and tears. These tears typically have a triangular shape, with the base of the tear overlying the entrance wound. Larger tears are associated with ammunition of .32 caliber or greater or magnum loads.

Stellate tears are not pathognomonic for contact wounds. Tangential wounds, ricochet or tumbling bullets, and some exit wounds may also be stellate in appearance. These wounds are distinguished from tight contact wounds by the absence of soot and powder within the wound. In some tight contact wounds, expanding skin is forced back against the muzzle of the gun, causing a characteristic pattern contusion called a muzzle contusion (Fig. 17.5). These patterns are helpful in determining the type of weapon (revolver or semiautomatic) used to inflict the injury and should be documented prior to wound debridement or surgery.

Figure 17.5

Contact Gunshot Wound with Muzzle Abrasion A contact gunshot wound to the right temple with stellate tears, seared skin, soot deposition, and muzzle imprint. A muzzle abrasion or muzzle imprint on the patient's right temple was the result of the injection of gases into the skin, causing a rapid and forceful expansion of the skin against the barrel of this 9-mm semiautomatic pistol. (Courtesy of William S. Smock, MD.)

With a loose contact wound, where the muzzle is angled or held loosely against the skin, soot and gunpowder residue will be present in and around the wound (Fig. 17.6). The angle between the muzzle and skin will determine the soot pattern. A perpendicular loose contact or near contact injury results in searing of the skin and deposition of the soot evenly around the wound. A tangential loose or near contact injury produces an elongated searing pattern and deposit of soot around the wound.

Figure 17.6

Loose-Contact Gunshot Wound Self-inflicted contact wound to the right upper chest with a 9-mm handgun. The wound margins display searing and soot deposition. (Courtesy of William S. Smock, MD.)

"Bullet wipe" is soot residue, soft lead, or lubricant, which may leave a gray rim or streak on the skin or clothing overlying an entrance wound (Fig. 17.7). This gray discoloration may also be found around the abrasion collar but is usually more prominent on clothing.

Figure 17.7

Bullet Wipe "Bullet wipe" is residue and lead deposited on clothing or skin. The presence of this residue on clothing may help to determine whether the wound is an entrance wound. (Courtesy of William S. Smock, MD.)

Exit Wounds

Determining whether a wound is an entrance or an exit wound should be based on the physical characteristics and physical evidence associated with the wound and never upon the size of the wound. Exit wounds are the result of a bullet pushing and stretching the skin from inside outward. The skin edges are generally everted, with sharp but irregular margins (Fig. 17.8). Abrasion collars, soot, searing, and tattooing are not associated with exit wounds. Soot can be seen at an atypical exit wound site if the entrance wound is close to the associated exit wound. Soot is propelled through the short wound tract and appears faintly on the exit wound surface.

Figure 17.8

Exit Gunshot Wound A stellate exit wound. Exit wounds may take on a variety of appearances. Stellate exit wounds should not be confused with contact wounds. The lack of soot and seared skin tells the physician that this is an exit wound. (Courtesy of William S. Smock, MD.)

Exit wounds assume a variety of shapes and appearances and are not consistently larger than their corresponding entrance wounds. The size of an exit wound is determined primarily by the amount of energy possessed by the bullet as it exits the skin and by the bullet's size, shape, and attitude. A bullet's usual nose-first attitude will change upon entering the skin to a tumbling and yawing one. A bullet with sufficient energy to exit the skin in a sideways attitude or one that has increased its surface area by mushrooming may produce an exit wound larger than its entrance wound. Energy transferred to bone, with resultant ballistic fracture, may also result in a exit wound larger than the entrance wound (Fig. 17.9). A "false abrasion collar" or "shored exit" wound may mimic an entrance wound. This occurs when the epithelium is pressed against a supporting surface such as a floor, wall, chair, or firm mattress (Fig. 17.10).

Figure 17.9

High-Velocity Gunshot Wound A perforating high-velocity gunshot wound to a lower extremity. The gaping exit wound resulted from the transfer of energy from the projectile to the tibia. The impact propelled multiple bony fragments through the skin. (Courtesy of William S. Smock, MD.)

Figure 17.10

Shored Gunshot Exit Wound A "shored exit" or "false abrasion collar" associated with a gunshot wound of exit. The false abrasion collar results when the skin is supported by a firm surface as the bullet exits. Shored exits occur when epithelium is pressed against a supporting surface (i.e., floor, wall, chair, or firm mattress). (Courtesy of William S. Smock, MD.)

Graze Wounds

Graze wounds are considered atypical and result from tangential contact with a passing bullet. The direction of the bullet's path is determined by careful wound examination. The bullet produces a trough with formation of skin tags on the lateral wound margins (Fig. 17.11). The base of these tags point toward the weapon and away from the direction of bullet travel.

Figure 17.11

Graze Gunshot Wound A superficial graze wound from a 9-mm projectile. Determining the directionality of a graze wound is difficult. The dark wound margins are the result of drying artifact and should not be confused with the deposition of soot. (Courtesy of William S. Smock, MD.)

Forensic Pearls

1. Distant-range gunshot wounds are inflicted from a distance greater than 4 ft and typically there is no tattooing, soot, or searing associated with the wound.

2. Intermediate-range gunshot wounds are inflicted at a distance from 1 cm to 4 ft and characteristically are associated with tattooing from burned and unburned gunpowder imbedded in the skin.

3. Near or close-contact gunshot wounds are defined as the maximum range at which soot is deposited on the wound or clothing and typically occur at a distance of 6 in. or less.

4. Contact gunshot wounds (barrel is in contact with the skin or clothing at time of discharge) vary in appearance but frequently include triangular tears, searing, and gunpowder within the wound.

5. Abrasion collars, soot, searing, and tattooing are not associated with exit wounds.

6. Determination of whether a wound is an entrance or exit wound should be based on the physical characteristics of the wound and clothing and not on the size of the wound.

7. Emergency physicians should attempt to recognize, preserve, and collect short-lived evidence whenever the clinical situation allows.

Forensic Medicine: Introduction

Every "weapon" (hand, belt, hot iron, knife, electrical cord, baseball bat, tire iron) leaves a mark, design, or pattern stamped or imprinted upon or just below the level of the epithelium. The imprints of these weapons are called pattern injuries, which are considerably reproducible. These injuries can be categorized into three major classifications according to their source: blunt force, sharp force, and thermal pattern injuries.

Sharp-Force-Pattern Injuries

Associated Clinical Features

There are two types of sharp-force injuries: incised and stabbed. The incised wound is longer than it is deep. The stab wound is defined as a puncture wound that is deeper than it is wide. The wound margins of sharp-force injuries are clean and lack the abraded edges of injuries from blunt forces. Forensic information can be gathered during the examination of a stab wound. Some characteristics of a knife blade, single- or double-edged, can be determined by visual inspection (Figs. 17.12, 17.13, and 17.14). Characteristics such as serrated versus sharp can be determined if the blade was drawn across the skin during insertion or withdrawal from the victim. Serrated blades do not always leave these characteristic marks.

Figure 17.12

Stab Wound A stab wound from a single-edged knife blade will impart a sharp edge and an dull edge to the wound. If the blade penetrates to the proximal portion of the blade, a contusion may result from contact with the hilt of the knife.

Figure 17.13

Single-Edge Stab Wound with Hilt Mark A single-edged stab wound with a small hilt mark associated with the dull edge of the blade. (Courtesy of William S. Smock, MD.)

Figure 17.14

Single-Edge Stab Wound A stab wound from a single-edged knife blade. The left side of the wound corresponds with the dull edge of the blade and the right side with the sharp edge of the blade. (Courtesy of William S. Smock, MD.)

Forensic Pearls

1. Incised wounds are longer than they are deep.

2. Stab wounds are puncture wounds that are deeper than they are long.

3. Knife-blade characteristics (single or dual edged, serrated or smooth) can frequently be determined by visual inspection of the wound.

Blunt-Force-Pattern Injuries

Associated Clinical Features

The most common blunt force is the contusion (Fig. 17.15). The pattern contusion is a common injury that helps identify the causative weapon. A blow from a linear object leaves a contusion that is characterized by a set of parallel lines separated by an area of central clearing. The blood underlying the striking object is forcibly displaced to the sides, which accounts for the pattern's appearance. Pattern injuries that an emergency physician should recognize include those caused by the hand (slap marks, fingertip contusions, grab marks, choke holds, fingernail abrasions), solid objects (baseball bat, tire iron, 2 by 4, belt, shoe, comb), and bite marks (Figs. 17.16, 17.17, and 17.18).

Figure 17.15

Fingertip Contusion Pattern This patient exhibits fingertip contusions as well as a web-space contusion. These injuries are the result of being choked by her assailant's left hand. (Courtesy of William S. Smock, MD.)

Figure 17.16

Grab-Mark Pattern Contusions This victim of domestic assault has two patterns of injury present over the outer aspect of her upper arm. The contusion on the left reveals a central clearing bordered by two parallel lines, which is the result of forceful contact with an extended finger. The contusion on the right is the result of fingertip pressure applied by the thumb of her assailant. (Courtesy of William S. Smock, MD.)

Figure 17.17

Slap-Mark Pattern Contusions This victim of assault presents with two pattern injuries. Diagonally oriented across both buttocks are pattern contusions with central clearing as well as parallel contusions. The vertically oriented contusions are the result of forceful contact as a blow was delivered with an open hand. The presence of these vertical contusions is virtually pathognomonic of inflicted injury. (Courtesy of William S. Smock, MD.)

Figure 17.18

Police Baton Contusions This patient sustained multiple blows from a police baton during his arrest. The central clearing bordered by two parallel contusions is indicative of impact with a rounded linear object. (Courtesy of William S. Smock, MD.)

Other manifestations of blunt force trauma to the skin are the abrasion and the laceration. A weapon with a unique shape or configuration may stamp a mirror image of itself on the skin (Fig. 17.19). The presence of a subconjunctival hemorrhage may be suggestive of choking, strangulation, or suffocation.

Figure 17.19

Carpet-Weave Pattern Abrasion A pattern abrasion of the forehead from a domestic assault. The weave of the carpet is appreciated on the outer margins of the abrasions. This injury occurred when the patient's forehead was slammed into the carpet. (Courtesy of William S. Smock, MD.)

Forensic Pearls

1. A contusion is the most common blunt-force injury pattern.

2. Blood underlying the force of the contusion is displaced to either side of the object, causing a pattern contusion in the shape of that object.

3. Emergency physicians must be able to recognize the pattern injuries caused by the hand, solid objects, and bites.

Thermal-Pattern Injuries

Associated Clinical Features

A thermal-pattern injury is a common form of abuse or assault, especially in children and the elderly. The detailed history of the incident should include the position of the patient relative to the thermal source. This will help determine whether the injury was inflicted or accidental. Pattern thermal injuries commonly encountered in the ED include flatiron burns, curling-iron burns, immersion burns, and splash burns (Figs. 17.20, 17.21, and 17.22). Immersion or dipping burns are characterized by a sharp or clear line of demarcation between burned and unburned tissue. In contrast, splash burns are characterized by an irregular or undulating line or by isolated areas of thermal injury, usually round or oval in shape, caused by droplets of hot liquid. The severity of the scald injury depends upon the length of the time the skin was in contact with the offending substance and the temperature of the substance itself. Tap or faucet water causes full-thickness thermal damage in 1 s at 70°C, and 180 s at 48.9°C. Law enforcement agents routinely measure the household's or institution's water temperature in any investigation involving a scald injury of a child, a developmentally delayed person, or an elderly patient.

Figure 17.20

Clothes-Iron Thermal Injury Pattern A thermal injury inflicted by an iron. The areas of sparing are associated with the iron's steam holes. (Courtesy of William S. Smock, MD.)

Figure 17.21

Scald Burn Thermal Injury Pattern Superficial and partial-thickness burns were noted on the patient's anterior surface only. The areas of abdominal sparing indicate that the victim was flexed and curled at the time of injury. The child's caretaker, the mother's boyfriend, admitted to holding the child under a running hot-water tap. Partial-thickness burns on the penis and medial thighs are indicative of pooling of the liquid in those areas, resulting in a time-dependent injury. (Courtesy of William S. Smock, MD.)

Figure 17.22

Immersion-Line Thermal Injury Pattern A classic "immersion line" is seen in a thermal-pattern injury. The line of demarcation is associated with the depth of the immersion. (Courtesy of William S. Smock, MD.)

Forensic Pearls

1. A thermal-pattern injury is a common form of abuse seen in infants, institutionalized patients, and the elderly.

2. Emergency physicians must recognize thermal-pattern injuries of abuse.