Wounding Capacity

The resulting tissue damage from a projectile injury can occur in three ways: from laceration or crushing, by cavitation, and through shock waves. Tissue damage occurs along the path of the projectile or the path its fragments travel through the animal’s body. A temporary wound cavity is created by outward expansion, stretching, and tearing of tissue along the projectile pathway. The pulsating collapse of the temporary cavity can result in the development of a permanent cavity.

During the formation of a wound cavity, both crush and stretch forces affect tissue, and a multiphase medium is created around the projectile as it travels through the tissue. The phases involve fluid composed of blood, lymph, and cellular fluids, surrounded by a radially disseminated phase of solid tissue. The radially accelerated tissue may cause an abrasion ring in the entry wound and can cause back-spatter if tissue is removed from the wound cavity. There can be a gas phase, formed by air within the tissue and/or gas generated by the projectile. The creation of the wound cavity also creates a vacuum that may pull hair or debris into an entry wound (Merck, 2013; Bradley-Siemens & Brower, 2016).

The type of tissue along the projectile trajectory will influence the degree of damage produced. Elastic tissues that give on impact, including lung or muscle, are more resistant to injury, especially from cavitation (DiMaio, 1999; Santucci & Chang, 2004; Bradley-Siemens & Brower, 2016; Bradley-Siemens et al., 2018). Soft tissue of thicker consistency such as liver and brain and dense rigid tissue like bone have greater resistance, increasing the level of energy transfer (Clasper, 2001; Santucci & Chang, 2004; Bradley-Siemens & Brower, 2016). Projectile-caused bone fractures are dependent on the type of bone and the angle of impact. For instance, cancellous bone is softer, increasing its ability to absorb energy, causing less fragmentation. Cortical bone, with its greater density, may fracture and fragment. When a projectile strikes the skull, increased intracranial pressure can contribute to concentric fractures forming target-shaped fracture lines. When a projectile has contact with bone, there is a deceleration, deformation, and possibly fragmentation or tumbling effect on the bullet and/or bone itself. Bone fragments may act as additional projectiles and may affect the range

Wound Analysis and direction of the primary projectile (DiMaio, 1999; Clasper, 2001; Bradley-Siemens & Brower, 2016). Tissue consistency may also affect drag on a projectile’s terminal ballistics, changing the velocity it travels through the tissue (Bradley-Siemens & Brower, 2016).

Wound Analysis

Whether the animal gunshot victim is alive or deceased will have to be considered in wound analysis. Findings may be relatively straightforward, as in the case of a single gunshot wound with a retained projectile, or more complex with multiple gunshot wounds. In the event the animal is alive you may be able to access the projectile. Multiple gunshot wounds and/or projectiles (such as shotgun pellets), through-and-through wounds with little or no projectile fragmentation, and the generation of secondary projectiles from bone fragments can all complicate analysis and interpretation (Jason, 2004; Merck, 2013; Bradley-Siemens et al., 2018).

Projectile injuries must be differentiated from other injuries, including wounds from motor vehicles, animal bites, and lacerations. In the absence of an accurate history of the injuries, wholebody radiographs prior to the examination need to be obtained. Examination findings consistent with trauma, including projectile-caused injuries, encompass hemorrhage, fractured organs (liver and spleen), bone fractures, and emboli (Bradley-Siemens et al., 2018). Projectile injuries are indicated by the presence of entry, exit, and intermediary wounds. It is essential that these lesions are identified and documented during the external examination of the live or deceased animal victim. Determination of entry versus exit wounds and establishing whether an intermediary wound exists is critical when conducting a complete projectile injury forensic physical or postmortem external examination (Bradley-Siemens & Brower, 2016).

Projectile wounds can be penetrating or perforating. A penetrating wound occurs when the projectile enters the animal’s body and does not exit. A perforating wound occurs when a projectile passes completely through the body of the animal. Projectile wounds can be further classified as graze or tangential. Graze wounds involve the projectile striking the skin at a shallow angle, causing an abrasion. A tangential wound causes the skin to be torn to the level of the subcutaneous tissue (DiMaio, 1999; Merck, 2013; Bradley-Siemens & Brower, 2016).

Entrance Wounds

An entrance wound usually has sharp margins. Entry wounds appear as a punched-out circular hole, usually of a small diameter. The diameter of the wound may be similar to the projectile. There may be an abrasion ring (collar) around the periphery of the wound and an inward indentation of the skin or fur (Bradley-Siemens & Brower, 2016) (Figure 9.8).

Entrance wounds can have soot marks, also referred to stippling or tattooing, or an abrasion ring from the discharge of the projectile if it was shot at close to intermediate range. When a firearm is discharged, in addition to the powder, soot from the ignition of the gunpowder emerges from the muzzle. Soot is carbon and contains vaporized metals from the primer, projectile, and cartridge case. If the muzzle of the firearm is held close to the animal’s body, soot may be deposited on the animal. These marks may be found on exposed skin; however, long or dense fur can alter these findings. The “flame” or muzzle flash may cause searing of the skin or fur around contact and near-contact gunshot entrance wounds (DiMaio, 1999; Bradley-Siemens & Brower, 2016). Soot or burned fur may still be present and thus it is important to obtain samples of fur over projectile wounds before further examination of the entrance wound. The size, intensity, and appearance of the soot pattern and range at which it occurs will depend on multiple factors, consisting of range of fire, type of gunpowder, angle of the weapon muzzle to the animal body, barrel length of the firearm, firearm caliber, type of gun, and the type of target. Most regions on an animal victim to

Figure 9.8 Entrance wound with abrasion ring.

be examined will have hair and it will be necessary to sample fur for gunpowder or soot. It will also be required to shave the area around the gunshot wound to discover any evidence on the skin beneath the fur (DiMaio, 1999; Merck, 2013; Bradley-Siemens & Brower, 2016; Bradley-Siemens et al., 2018).

Intermediary Wounds

This type of wound occurs when a projectile passes through one part of the body and enters another part, causing a reentry wound. This reentry wound will not normally have an abrasion ring. This can help differentiate it from an entrance wound. An intermediary wound can develop when a projectile passes through an intermediary object, including a door, wall, or window before entering the animal’s body. Either situation can alter the appearance and number of entry wounds and will make wound interpretation more difficult (Merck, 2013; Bradley-Siemens & Brower, 2016; Bradley-Siemens et al., 2018).

Exit Wounds

An exit wound usually has jagged margins and a larger diameter than an entrance wound. The jagged margins can consist of slit-shaped, stellate, or irregular patterns. There usually is no abrasion ring with gunshot residue. There may be protruding underlying tissue or bone (Merck, 2013; Bradley-Siemens & Brower, 2016; Bradley-Siemens et al., 2018) (Figure 9.9).