In general terms guns can be divided into smoothbore and rifled weapons, the former being more commonly encountered in Ireland.
The appearance and severity of the gunshot injuries depend on the type of weapon, the type of projectile, secondary projectile, and the distance or range of fire. When a weapon is fired not only is a projectile, bullet, or pellet mass, emitted from the barrel but also gasses of combustion that are flame, smoke, unburnt powder, and carbon monoxide, as well wads from shotgun cartridges.
These weapons were designed to kill animals. The most common example is the shotgun, which may be single or double-barrelled. The normal barrel length is between 18 and 36″. However in homicidal shotgun wounds, the weapon will often have had the barrel shortened or sawn-off, usually to <25 cm or 10″ as a weapon with a shortened barrel is easier to conceal. However, altering the length of the barrel can have a marked effect on the efficacy and efficiency of the weapon as it can decrease the missile velocity by about 20% and the shot may spread earlier. This can have the effect of increasing the diameter of pellet spread on the skin surface to double that expected for the range of fire.
The effective range for a shotgun is approximately 50m. This range can be improved if the end of the barrel is narrowed to keep the shot together for a greater distance, this is termed choking. Shotgun weapons can be fired two or three times faster than rifled weapons but are less accurate than rifled weapons. In a shotgun there are single or multiple missiles or pellets, fired from the same shell. At close range, these wounds are similar to a high-velocity type of wound. The wounds produced by gunshot injuries can be nonpenetrating, contusions and abrasions, equivalent to a blast injury, penetrating, with an entry and no exit, or perforating with an entry and an exit.
Read Also: Smoothbore Weapons
The appearance of the entry wound depends on the distance from which the shotgun is fired. As well as the pellets secondary projectiles are emitted from the barrel of the gun. These include flame, soot, or smoke and particles of unburnt powder which accompany the cartridge contents that is the wadding or packing material around the shot.
In contact injuries, the pellets enter the body as a solid mass-producing a single entry wound. The entry hole will be roughly the diameter of the barrel. There may be a contact abrasion around the entry wound and pink discoloration of the wound margin due to the presence of carboxymyoglobin, carbon monoxide being one of the fire gasses emitted from the barrel. In double-barrelled weapons, the imprint of the other barrel may also be evident on this skin surface. The secondary projectiles such as soot, powder, wads will all be within the wound, although there may be a little scorching of the wound margins. Contact injuries to the head show a large and irregular or stellate entry hole and those inside the mouth show stretch marks radiating from the mouth due to the explosive action of the gasses.
Loose contact injuries are similar to contact but, with either no, or an incomplete, abrasion around the wound and soot or smoke on the skin around the wound. As the end of the barrel moves further from the body the appearance of the wound alters.
For close, near discharge, of a few centimeters, there will be a single entry hole but no contact abrasion, but there will be evidence of the secondary projectile, including scorching of the wound margin due to the flame, blackening of the skin around the wound margin due to smoke and tattooing or stippling around the wound margins due to unburnt powder particles. In close range, probably up to 15 cm or so, scorching, smoke blackening, and tattooing may be present.
In intermediate-range injuries. 20 to 100 cm, as the gun moves further away, there is no evidence of scorching and the blackening around the wound becomes less dense eventually dissipating and leaving only powder tattooing on this skin. Up to about 10 cm, there can be flame charring around the wound, up to about 15 cm. There would smoke and shoot around the wound and up to 50 cm. There could be unburned powder tattooing depending on the type of powder. Eventually, tattooing disappears at about 60 cm or so from the body. Up to this distance, the shot and the wad traveled together as a compact mass.
With a distance of one meter, up to 2m, the wad may separate from the shot mass, and being fairly light, will lose velocity and fall off and may strike the skin adjacent to the shotgun entry hole caused by the mass of pellets leaving a wad mark on the body. There is still a single entry hole but this now has an irregular edge, as the pellet mass begins to spread out.
At the distance increase further, more than 2m the wad will fall away before striking the body and the single mass of pellets will start to disperse. Stray pellets will strike the skin around the main entry hole indicating pellet scatter. The extent of this scatter will increase, the diameter of spread on the skin increasing as the distance increases.
The central hole decreases in size until at about 8 to 10m there is no central hole, only individual pellet holes. Distant shotgun injuries are rarely fatal as the shot is diffusely dispersed.
Only at close range. More likely in head injuries.
Rifled weapons were designed to kill men. They are so-called because of grooving on the inside of the barrel which improves the gyroscopic steadiness of the bullet by spiraling or spinning the bullet along the length of the barrel, the emerging bullet spinning as well as being ejected forwards. Rifling off the inside of the barrel produces parallel spiraling grooves along the inside of the barrel, separated by raised areas known as lands. There are usually between 4 to 7 parallel grooves, with either a left or right-handed twist. As the bullet passes along the barrel these will mark the surface of the bullet and these marks may assist in identifying the weapon from which the bullet was fired.
Rifled weapons are divided into short-barreled handguns or long-barrelled guns. Short barrelled guns include revolvers, pistols, and sub-machine guns.
To fire a rifled weapon requires a degree of force. If the hammer is cocked it requires 1 to 21bs. to pull the trigger. However, if the weapon is uncocked it requires 5 to 61bs. to pull the trigger.
The rifled weapons fire bullets. Revolvers and pistols tend to be low-velocity weapons, the revolver firing a bullet at 600′ per second, the pistol at 1000′ per second. This is insufficient to knock a body off its feet. In contrast, the higher velocity weapons are the rifles, ranging from 2000′ per second and having the potential to inflict more injuries.
Bullets have a specific shape with a pointed nose making them more aerodynamically sound. Round-nosed bullets will cause more damage to a body. They are generally made from soft lead, although they may have a small amount of antimony for hardness. Because of this, they are often jacketed, the lead enveloped in a jacket of brass, aluminum, bronze, or steel. Depending on the type of damage intended, the bullets can be non-jacketed, jacketed, or partially jacketed, for example; hollow nose bullets have a jacket, but the weapon acts as a non-jacketed bullet when it strikes its target, as it distorts and slows, and causes more damage.
Read Also: Rifled Weapons
Contact rifled gunshot wounds will show a single entry hole, usually regular and round, slightly smaller than the diameter of the bullet with inverted edges, but it may be ragged or star shape over bone. There may be little or no rim of abrasion around the wound but there may be a bruise or imprint abrasion due to the recoil of the barrel. In some cases, there may be a grease stain, or bullet wipe, around the entry hole, caused as a bullet penetrates the skin.
In hard contact wounds, there will be no soot around the entry hole, although in loose contact there may be a narrow rim of the soot. All these secondary projectiles, smoke, soot, and powder, will be inside the wound. In contact rifle injuries there may be a patterned soot mark around the wound if there are vents on the barrel. For example, if a silencer is used.
At close range, less than a meter, there will be a single entry wound. There will be varying degrees of flame damage, soot or smoke staining, tattooing, or powder abrasions around the wound, depending on the type of powder used and in particular the shape and size of the powder grains. As the distance increases the presence of secondary projectile decreases.
At more than a few meters, out with the range of the secondary projectiles, the bullet entry hole comprises a neat entry wound, with an abrasion collar and the edge inverted. Generally, the entry hole is less than the diameter of the bullet. However as the distance increases the bullet may not strike perpendicular to the target, due to tail wag, which is when the bullet loses its gyroscopic properties, which may cause it to strike the target at an angle, producing a larger and irregular entry hole. Also if the bullet has already passed through an intermediary target the entry hole on the main target may be irregular, with some splitting of the skin margins around the entry wound.
As the distance increases the entry and exit wounds from rifled weapons have a similar appearance but there may be a grease stain around the entry hole.
Only at close range for example injuries to the head, would there be an exit wound in a shotgun injury. The most resistance projectiles will meet is this skin which is tough and has a resistance equivalent to several centimeters of muscle. Shotgun pellets are stopped by the bones.
In gunshot wounds from rifled weapons, the exit wound may be irregular, depending on the angle of the bullet as it leaves the body. In some cases, the wound may be stellate and star-shaped but the edges are everted. There is no grease staining around the wound margin and no marginal abrasion. In a high-velocity weapon that is a rifle or an Armalite weapon, the entry and exit wounds are often similar.
The appearance of the injuries and the severity of the injuries depends on the range of fire, relative directional angle of the projectile entering the body, the type of weapon or ammunition, and the presence of an intermediary target.
Firearm residues are most commonly seen in close discharge. It is most likely present on clothing and not on the skin of the clothed area. However, grains may be driven through the clothing at a distance of less than 30cm. Gunpowder grains may be visible but other forms of firearm powder may be invisible. The firearm residues travel short distances usually 7 cm to 15 cm and can be found on the person who fired the gun, the person near to the gun as it is fired, or any person who has handled a residue-bearing weapon. This can be tested by swabbing with 5% analytical grade nitric acid and trace metals can be quantified by flame-less atomic absorption spectrometer. The primer residues contain lead Stifnate, lead peroxide, barium nitrate, antimony, etc, the proportion of each depending on the brand of primer which was used.
It provides permanent documentation of the number of bullets and fragments, the position of the bullet, and some of the injuries.
They may identify all bullets or pellets within the body, including pellet emboli. X- raying is vital if the body surface is altered by fire, decomposition, or animal activity.