Air-powered weapons

These range from simple, low-powered, smooth-bored guns, usually referred to as ‘air-guns’, to sophisticated high-powered air-rifles. The power is delivered by air that is compressed by the action of cocking the weapon or by pumping a lever. In gas-powered weapons, compressed carbon dioxide from a disposable cylinder is used. Air-powered weapons fire single pellets. The common calibres for air-powered weapons are 0.177, 0.2, 0.22 and 0.25 inches.

Shotgun

These weapons are single or double barrelled. The barrels are smooth-bored and the shotgun discharges multiple pellets in a mass each time it is fired. There is a variety of barrel lengths and calibres,¹ the calibre of the barrel usually being referred to as the ‘bore’ or ‘gauge’. The 12-bore (0.729 inches/18.2 mm) is probably the most commonly used shotgun. An exception to the classification of ‘bore’ size is the ‘410’, which refers to the actual diameter of the barrel (0.410 inches) and is the smallest of the commonly encountered shotguns.

Rifles

Rifles are characterised by having spiral grooves along the length of the internal surface of the barrel. These grooves cause the bullet to rotate along its longitudinal axis and this rotation, or spin, stabilises the bullet and prevents it from turning end over end whilst it is travelling through the air.

There are many calibres of rifle. Common hunting rifle calibres include .22, .243 and .270 (range 5.7–7 mm).² Rifles are further categorised by the method of ignition of the explosive charge in the cartridge. Those in which the firing pin strikes the rim of the cartridge are known as ‘rimfire’, whereas those that strike a central primer in the cartridge are called ‘centrefire’ rifles.

Generally, rimfire rifles are restricted to the ubiquitous .22 calibre, firing solid-nosed or hollow-nosed bullets with muzzle velocities ranging from 1000 to 1500 feet per second (fps). Centrefire rifles fire bullets with considerably greater muzzle velocities: 2400–4000 fps.

Air-rifle pellets

The pellets used in air-guns and air-rifles are the same, and are usually constructed of soft lead. The diabolo type of pellet has a narrow waist and a rounded point. Other lead pellets have straight sides and a more conical point. In the ‘Prometheus’, a polished zinc head is enveloped in a flexible synthetic jacket. This pellet is reputed to be capable of penetrating steel and so may be potentially more dangerous in head injuries.³ The ‘Sabo’ pellet is also of compound construction, having lead and plastic components. Fragmentation of these two types of pellet can result in separation of the radio-opaque head of the pellet from the radio-lucent nylon or plastic part that remains within the wound track.

‘BB’ ammunition for air-guns is spherical lead shot that derives its name from the original method of describing the size of the lead balls. In this case, the shot size was between ‘B’ and ‘BBB’.

Shotgun cartridges

The cartridge (Fig. 8.1) consists of several parts:

Fig. 8.1 Diagrammatic representation of the main elements of a shotgun cartridge.

Rifle bullets

The cartridge case is usually of copper/zinc and contains the primer at the flat end and the propellant (explosive charge) in the middle part. At the forward end, the cartridge case is crimped around the bullet that protrudes from the point (Fig. 8.2).

Fig. 8.2 Diagrammatic representation of the main elements of a rifle bullet.

The bullet can be solid in construction (usually lead) and may be covered by a very thin layer of copper. Lead bullets are suitable only for rimfire weapons. Centrefire ammunition has a lead or steel core covered by a metal jacket that prevents the bullet melting or fragmenting as it travels down the barrel at high velocity. Most hunting ammunition has a ‘partial metal jacket’, meaning that the tip of the bullet is non-jacketed in order to maximise deformation of the bullet when striking the target.

Radiography

After initial examination of the outside of the body for evidence of bleeding or matted hair and feathers, a series of radiographs of the head, body and limbs, including the feet, may provide the first tangible evidence of pellets or bullet fragments.

Radiographs are of great assistance in the search for pellets or bullet fragments at post-mortem examination. However, to overcome the limitations inherent in the two-dimensional nature of radiographs, it is essential to have dorsoventral and lateral views. In addition, radiographs may indicate the track of the bullet through the body. This is of particular importance if the bullet has exited from the body.

Radiographs can aid in establishing, early in the investigation, which type of weapon was used (shotgun, rifle or air-rifle). Fragmentation patterns, as seen in radiographs, can be helpful in identifying the type of ammunition. For example, on striking dense bone, low-velocity .22 bullets break into a variable number of large and small radio-opaque fragments (Fig. 8.3). The greater energy associated with high-velocity bullets causes these bullets to disintegrate to a greater extent and may result in the fragmentation pattern commonly known as a ‘lead snowstorm’ (Fig. 8.4).

Fig. 8.3 Radiograph of roe deer head showing the fragmentation pattern of a low-velocity .22 bullet extending from the back of the head to the nose.

Fig. 8.4 Radiograph of bull’s neck showing fragmentation pattern (‘lead snowstorm’) of a fragile, high-velocity bullet (.22–.250) commencing at the skin and extending to the spinal column. Note also a small number of shotgun pellets at the right side.

Separation of the core of a hunting bullet from the copper jacket may result in exit of the core with retention of the jacket in the cadaver. Rifling marks, used by ballistics experts to match bullets to suspect rifles, are present on the jackets of jacketed bullets and radiographic examination will assist in recovery of these valuable fragments.

On rare occasions, very forcible fracture of, for example, the femur of a fit and energetic horse can result in wounds caused by exiting bone fragments. These may be mistaken for bullet wounds. Radiography provides reassurance that firearms were not involved.

General

In most cases the entry holes, and to a lesser extent the exit holes, will be obscured by hair or feathers. Clipping the hair or careful plucking of the feathers is necessary to reveal the skin wounds (Figs 8.5 & 8.6). Clipping the entire side of an animal will give a clear indication of the scatter of shotgun pellet injury (Fig. 8.7). Depending on the stance, position or action of the victim (e.g. flying, running, stretching, jumping), the skin wounds may or may not lie directly over deeper injuries found at post-mortem examination. Initial observations should include a description of surrounding bruising and the size and shape of hole. Frequently, feathers or tufts of hair are drawn into an entry hole and provide convincing evidence that penetration occurred at these sites. Usually these hairs or feathers are found in the skin or subcutaneous tissues, but on occasion they may penetrate more deeply to the body cavities and the internal organs (Fig. 8.8).

Fig. 8.5 Cat showing entrance hole of a .22 bullet in the right flank. This hole was visible only after hair clipping.

Fig. 8.6 Cat (as in Fig. 8.5) showing exit hole in left side. This hole is marginally larger than the entrance hole and shows a halo of bruising.

Stay updated, free articles. Join our Telegram channel

Join