FIREARM INJURIES
Rationale:
Injuries due to firearms are a major health problem which impact severely on the criminal justice as well as the health care systems.
The use of firearm in criminal activities appears to be increasing.
Injuries, but also other causes of homicide, accident and suicide occur.
The rise of international terrorism has also made some knowledge of such injuries desirable.
Firearms are weapons designed to prope1 a projectile through the expansion of gases which are generated by the combustion of an explosive substance.
All mechanical traumas —except deceleration injuries are caused by the transfer of energy from external moving object to the tissues. This is very
obvious in shooting, where the nature of firearm wounds varies considerably from other types of injuries...
Firearm weapons:
Weapons are of two types; rifled or nonrifled.
I-Rifled weapons (Gunshots):
The inner surface of the barrel shows spiral grooves with lands in between. The missile of this type of weapons is bullet i.e. it fires bullets. The lands bite the bullet as it passes through the bore giving the bullet its spiraling, spinning motion. The number of land. and groove impressions on the bullet (primary rifle marks) are specific characters, for each type of weapon and are known as family characteristic.
The bore diameter of the barrel of rifled weapons is called caliber and refers to the distance between two opposite lands. It is expressed in hundredth of an inch or in mm.
Rifled weapons are either of long barrels e.g. service rifle, or of short barrels (hand guns) e.g. revolver or pistol.
Mechanism of firing rifled weapons: ‘
In order to understand the sequence of events that Occur on firing a weapon, the parts of a cartridge should be well known .
The base contains a capsule containing a primer charged with mercury fulminate as explosive
1. When the trigger is pulled, the impact of the firing pin ignites the explosive.
2. The flash fire (or the flame from detonating the primer) ignites the propellant powder in the cartridge:
3. The rapid burning of the powder with the production of a relatively enormous amount of gas in a confined space cause high pressure.
4. This pressure results in driving the bullet out of mouth of the case and out of the barrel of the gun.
Effects of gunfire in rifled weapons:
The components of the gunfire that cause changes on the skin and clothes are gases, Flame, smoke, gunpowder, metallic fragments and the. missile (bullet).
1. The gas leads to eversion of edges of the wound and cruciate shape
lesion.
2. The effect of flame is burning.
3. Smoke produces blackening or smudging on the surface of the target. It is more evident when the powder is black.
4. The unburned particles or powder residue enter the skin in a scattered form and are deposited in the dermis and lodged in the epidermis. This pattern is called tattooing or stippling.
5. Bullet causes: tissue damage or defect (loss of substance). When the bullet strikes the skin it pushes the skin so much that it is stretched to a point of rupture. The bullet enters the - body through the rupture (entrance or inlet).
Since the rifling of the gun gives a rotational movement to the bullet, it not only makes the hole, but because the rotating bullet rubs against the stretched margins of the hole, it causes a rim of abrasion at the margin of the wound.
While the bullet is passing through the defect created by its nose, the diameter of the wound is greater than the diameter of the bullet. After the bullet leaves the skin and enters deeper tissue, the elasticity of the skin causes the wound to shrink. Then the inlet wound has a diameter smaller than the diameter of the bullet.
6. Lubricant effect: Lubricant from the gun barrel and bullet is wiped off or rubbed off from the bullet surface and deposited on the margin of the wound; grease ring grease mark.
7. Metal effect: metal fragments become embedded •in skin (gunshot residue). Their origins are from the barrel and the bullet itself
8. Muzzle effect: Imprints of muzzle occurs in contact, firing due to simple continuous pressure of the muzzle on the skin. Also gases blown intoand under the skin blast the skin outwards, causing it to strike against the muzzle.
9. Carbon monoxide in, the gases leads to increased amount of carboxyhemoglobin and carboxymyoglobinin the tissues giving it a
pink coloration.
Bullets produce tissue damage in three ways:
I. Laceration and crushing
2. Cavitations: permanent cavity is caused by thepath of the bullet itself, and temporary cavity is formed by continued forward acceleration of air or tissue, causing the wound cavity to be stretched outward.
3. Shock waves: compress the tissue and travel ahead of the bullet.
1. Bullet velocity and mass
2. Bullet design
3. The distance of the target from the muzzle
4. The type of tissue and the penetration. The density (specific gravity) and elasticity are the major tissue factors. The greater the specific gravity, the greater the damage, and the greater the elasticity, the less the damage. Thus, lung of lowdensity and high elasticity is damaged less than muscle with higher density but some elasticity. Liver, spleen and brain have no elasticity and are easily injured. Fluid-filled organs (bladder, heart, great vessels, bowel) can burst because of pressure waves .A bullet striking bone may cause fragmentation of bone.
5. Tumbling of bullet.
Range of firing of rifled weapons:
The components of gunfire produce characteristic changes and help to determine the distance of firing.
The estimation of the distance of firing is important
- To prove or disprove statements of the accused.
- To rule in or out the possibility of suicide.
- To help establish the nature of the accident.
Generally, the distance may be said to be contact, intermediate range (close-range), or distant range.
Contact wounds: characteristically have soot on the outside of the skin, and muzzle imprint, or laceration of the skin from effects of gases.
Contact wounds over bone: When the wound is made over a site with underlying bone eg. Scalp.. the large volume of gases cannot spread . So, the gas is reflected back by the underlying har4jjer (bone) momentarily raising a dome of skin and subcutaneous tissue. When the gas volume is large, this dome may split causing a stellateor cruciate Lesion.
Intermediate or close-range. wounds: may show a wide zone of powder stippling.
• Distant range wounds are lacking powderstippling and usually exhibit a hole roughly the caliber of the projectile fired.
The distance depends upon the spread and amount of residue deposited on the target and on the length of barrel. Therefore, to reach an accurate
estimation of the distance, test fire from various distances is needed to correlate the evidence pattern with the test.
Exit wounds:
Exit wounds are generally larger than entrance wounds due to the fact that the bullet has expanded or tumbled on its axis. Exit wounds usually do not exhibit gunshot residues.
The bullet path may be altered by striking bone or other firm tissues, such that the bullet track may not be linear, and exit wounds may not appear directly opposite entrance wounds.
Differences between inlet and exit of the bullet
Inlet of bullet / Exit of bulletTissue loss
Size / More
Smaller except in near firing and oblique firing / Less
larger
Edges / Inverted, except in
-Near firing
After putrefaction
Inlet in fatty area / Everted
Shape / Round or oval / Any shape: round, stellate, slit-like, cruciate.
Powder marks / Present except in :
Clothes
Ricocheting / Absent
Regularity / Regular except in
• Near firing
• Inlet in corrugated skin. / Irregular
.
Marginal abrasion and grease ring / Present / Absent
Gunshot residue / Present / Absent
Beveling / Internal / External
Beveling of bone
The bullet displaces the fragments of bone in the direction it travel. in the skull; the entrance shows a small rounded hole, in the outer table, larger in the inner table i.e. internal beveling. On exit from the cranium it causes smaller defect in the inner table and larger in the outer table (ie. external beveling. Beveling occurs also in sternum, iliac crest, scapula and ribs.
Direction of firing:
- If perpendicular, the inlet is rounded. Marginal abrasions show equal scraping on all sides.
- If the bullet strikes at an angle, the inlet is oval and abrasion on one side nearest to the gun.
- If it strikes at an angle but not enter i.e. grazes the skin and subcutaneous tissue. Grazing of bullet is elongated or oval.
Gutter wound: If a track is formed between exit and inlet which are only in skin and subcutaneous tissue due to internal deviation by impact on bone.
Special forms of firearm wounds:
1. Inlet wounds of bullets fired at a distance may be “F’ or “D”shaped due to tumbling of bullet in its flight, and there may be surrounding lacerations.
2. Ricochet bullet: a bullet is striking a firm object before entering the body, leaving powder marks on that object. The bullet may be deformed
• causing asymmetrical or irregular wound.
3. Presence of more than one exit:
- When the bullet breaks up in its course or the jacket is separated and has another exit.
- When bones fracture and fragments come out through separate opening.
When two bullets are fired in succession at one point i.e. the same inlet and 2 different exits.
Mechanism of firing sporting gun (nonrifled weapons):
When the trigger is pulled, the firing pin activates the primer. the
flash produced ignites the powder. The pressure of gas pushes the wad forwards. This blasts the pellets out of the shell. With the pellets, flame, smoke, unburned gun powder and wads come out from the barrel and cause effect on the skin.
Effects of gunfire in nonrifled weapons:
The effects of gases, flame, smoke and unburned particles are the same as in the rifled weapons, but they occur at different distances.
the effects of pellets and wads differ with distance too.
Range of firing in nonrifled weapons:
Contact wounds:
• Single circular entrance wound
• Soiling and burning are minimal
• Muzzle imprint
• Pink coloration to the interior of the wound track and adjacent tissues due to carbon monoxide
• Cardboard or felt wads or plastic cups are found within the depth of the wound,
• NB. Contact over bone: cruciate lesion due to splitting of the skin by the expanding gases,
0-15cm
Single circular wound if the weapon is held at right angle to the skin and elliptical if slanted.
• Singeing of hair around the wound.
• Burning and blackening.
• Pink coloration of the tissues within and around the wound due to
CO.
• Wads or plastic cups will be fund within the depth of the wound.
15 cm up to 2 meters:
• The edges of the wound will become scalloped and crenate (moth- eaten, rat- hole)
2m—4meters:
• Once beyond 2 in there will be no burning or blackening and rarely powder tattooing
• Entrance wound is surrounded by individual pellet holes (satellites) which start to appear. (NB. Old terminology starting. dispersion).
• The number of satellite pellet holes will progressively increase around the main wound which in turn diminishes as the distance increases.
More than 4 meters:
• Only individual pellet holes are seen
• Central hole is absent
• Known as full dispersion
Wad wounds:
• Caused by nonmetallic contents of shotgun cartridges.
• Vary from trivial bruises to fatal lacerations.
• New devices now used in Shotgun ammunition may cause characteristic wounds, such as the square edged star or capital X-shape from the wings of the opened plastic cup which contains the pellets.
• Felt and cardboard wads (used in old ammunition) travel a variable distance from the gun muzzle.
* Up to 2 meters wads will almost always enter the wound and should be recovered at autopsy to assist in identifying the type of ammunition.
• From 2 — 5 meters wads strike the skin causing circular bruise.
• Beyond this distance, wads will fall to the ground.
N.B: The distance varies with presence of choking, the length of barrel, the size of pellets, the gauge of gun and the design of pellets. The most important factor is the type of powder.
shocking: The shotgun barrel is narrowed at the muzzle end. This modifies the spread of pellets from the muzzle. They are kept together over a long distance.
NB. Range of fire: Precise estimates require comparison of wound pattern on skin / clothing with test patterns made by firing the same shotgun with same ammunition.
Exit wounds in nonrifled weapons:
It is uncommon to have exit, except if pellets strike the body at acute
angle and bones in the way, or at near firing..
INVESTIGATION FOR FIREARM INJURIES
The objectives here are to reach the answer of the following questions:
A. Is the case due to firearm?
B. Is it an inlet or an exit?
C. What is the type of weapon: rifled or nonrifled.
D. What was the range of firing?
E. What were the circumstances of injury?
F. What was (were) the cause(s) of death?
G, Specify the causative weapon
A. Characters of firearm wounds are:
1. Presence of tissue damage or defect due to cavitations (loss of substance).
2. Presence of inlet and exit, and a track in between.
3. Externally at the inlet: powder marks and gunshot residue and also along the track.
4. Presence of bullet or shots.
5. Bevelling of bones.
Complications and sequel of firearm:
These depend on site of injury, organs or blood vessels involved.
• Contact or near firing usually lead to instantaneous death.
• If the missile reaches the brain, laceration occurs.
• In the neck: paraplegia may occur if death is delayed. If the medulla oblongata is involved, death is instantaneous.
• In the chest; death occurs due to blood loss (hemorrhage) leading to circulatory failure.
• In the abdomen: hemorrhage or infection and peritonitis may be the cause of death.
• If fracture of long bones, fat embolism may occur.
• if long immobilization, pulmonary embolism may intervene.
G. SPECIFICATION OF THE FIREARM WEAPON:
Examination of clothing:
• A defect.
• Firearm residue: help establishment of inlets and exit, the distance and direction.
Firearm residue on victim with entrance: -
Some are visible as blackening, grease, tattooing and burning. Others are invisible. These are related to primer and powder. materials or to metal residues from bullet or cartridge case.
Residue may be found on the skin or clothing of the person who fired the gun, on an entrance wound of a victim, or on other target materials at the scene. The major primer elements arc lead, barium and antimony. Usually all theseare present. Modem gunpowder or smokeless powder cancontain many materials; nitrocellulose is always present, with other compounds containing nitrate and nitrogen.
X-ray
it is important for many reasons:
• To locate and identify the bullet, pellets, jacket or fragments.
• To delineate the track to outline the direction of fire.
• To determine defects in bone.
• To provide document for injuries present.
• To rule out the presence of a missile.
EXPLOSIVE INJURIES AND DEATHS
As the risk of terrorist attacks increases, disaster response personnel must understand the unique pathophysiology of injuries associated with explosions and must he prepared to assess and treat the people injured by them.
An explosion can be defined as the sudden and rapid escape of gases
from a confined space accompanied by high temperatures, violent shock, and loud noise.
Types of explosions:
I- Mechanical Explosion:
A mechanical explosion occurs due to a physical reaction such as overheating.
II- Chemical Explosion:
A chemical explosion is caused by the extremely rapid conversion of a solid or liquid explosive into gases.
Ill- Atomic Explosion:
An atomic explosion may be induced either by fission (splitting of the nucleus of atoms) or fusion (joining together of the nuclei of atoms).
Chemical explosions:
* A chemical explosion is an instantaneous chain of events in which an explosive material is rapidly converted into a gas under extremely high temperature and pressure.
• Based on the speed of the explosion, explosives are categorized as either high-order explosives (HE) or low-order explosives (LE).
Low-order Explosives:
• Loworder explosives involve deflagration (rapid burning that gives off intense heat and sparks).
• These explosions are subsonic (the explosive reaction is slower than the speed of sound) and lack HE’s over pressurized waves.
• Examples include:
o Napalm,
o Pipe bombs,
o Gunpowder, and
o Many petroleum-based explosives
High-order Explosives:
• High-order explosives involve supersonic explosions (the explosive detonates more quickly than the speed of sound) and blast over
pressurized impulse waves.
• Examples of HE include:
o hand grenades,
o TNT,
o Military bombs,
o Dynamite: invented by Alfred Nobel in 1890
oCD-4
o Semtex (a plastic explosive)
o Diesel fuel
o Nitroglycerin
o Ammonium nitrate fuel oil (ANFO) - Was used in the explosion of New York’s World Trade Centre in 1993.
o RDX invented by British during WWII (standing for Research Department Explosives). It is what military use today.
Blast injuries
The four basic mechanisms of blast injury are termed as primary, secondary, tertiary, and quaternary. “Blast Wave”, causing the primary injuries, refers to the intense over-pressurization impulse created by a detonated High order Explosive (HE). Blast injuries are characterized by anatomical and physiological changes from the direct or reflective over- pressurization force impacting the body’s surface.
Low order Explosives (LE) are classified differently because they lack the self-defining HE over-pressurization wave. LE’s mechanisms of injuries are characterized as due from ballistics (fragmentation), blast wind (not blast wave), and thermal effect. There is some overlap between LE descriptive mechanisms and HE’s Secondary, Tertiary, and Quaternary mechanisms.