Wound Ballistics
Wound ballistics also known as Terminal Ballistics is concerned with the wounding phenomenon. It studies how a projectile creates the wound and causes the destruction of tissues by its movements on and after entering the body, its travel inside and the exit from the body.
In a broad sense, the study of how wounding agents—such as bullets and fragments from explosive weapons—interact with tissue is known as wound ballistics. The physical simulation and measurement of the interaction of wounding agents with tissue is the laboratory aspect of wound ballistics.
A bullet or its fragments physically alter the tissue when they pass through it. This causes the tissue to take evasive action from the projectile’s front, lacerating and crushing it in different ways. The amount of kinetic energy available to carry out this activity determines the extent of the laceration and the degree of crushing.
Wound Profile
A helpful conceptual tool for providing a visual representation of the length, shape, and measurements of the whole track of the bullet or fragment is the “wound profile.” This may be determined from actual wounds or trails in gelatine, although Gelatin soap is the easiest substance to replicate and quantify.
The study of projectile motion is known as ballistics. It is studied at in four areas:
1. Interior Ballistics
This field studies the movement of bullets inside a gun’s barrel.
2. Exterior Ballistics:
Exterior Ballistics is the study of how projectiles move in the open (air) after leaving a gun’s muzzle.
3. Terminal Ballistics
This refers to the projectile’s velocity or behaviour at or within the target. It is also called Wound Ballistics.
4. Transitional Ballistics
The occurrences between the internal and exterior ballistic periods are covered by the transitional ballistics. It begins when the bullet exits the barrel’s muzzle and ends when the pressure inside the barrel reaches air pressure.
Wounding Mechanism
When a projectile impacts the human body, the skin, flesh, and bone beneath are depressed and compressed. The constant pressure extends them beyond their elastic limits, resulting in the formation of a hole. After the hole is formed and the bullet has entered, the stretched skin returns to its usual state. The diameter of the hole on the skin seems to be somewhat smaller on non-stretched skin than the size of the projectile that generated the wound when it was stretched.
The lowest velocity necessary to pierce human skin has been determined to be between 40 and 50 metres per second. The penetration velocity through a bone is 60 metres per second.
The projectile continues to move forward until it exits the body through an exit hole, or until its energy is expended in overcoming the resistance.
In subsequent situations, the projectile is discovered stuck near the tunnel’s terminus.
Elements Of Wound Ballistics
Wound ballistics has following important elements-
1. Nature of target.
2. Velocity of projectiles.
3. Constructional features of projectiles.
4. Range.
Firearm Injuries
Firearm bullets have numerous shapes, velocities, and kinetic energy than most other agents that cause injury. The wound patterns, the damaging effect on the tissues, the presence of foreign substances (of certain shapes and composition), and the projectile track all aid in determining whether or not a given injury is a gunshot injury.
The analysis of the injuries determines if the given damage is:
- a firearm injury or not.
- an entrance wound or an exit wound.
- post-mortem or ante-mortem injury.
- from the alleged firearm.
- Of alleged age
- fatal or not.
- such that a person could perform the alleged acts after receiving the given injuries.
- caused from alleged distance.
The evaluation of injuries can also indicate of the alleged number of shots fired or the number of firearms used.
Entrance Wound
Most of the time, the wounds have precise features that allow them to be identified without difficulty. The main features used for this aim are as follows:
1. In most cases, the wounds are round or oval. Wobbly bullets can also cause key hole wounds.
2. Normally, the diameter of the entrance hole is significantly smaller than the diameter of the bullet that created the hole.
3. The edges have been compressed inward – they have become inverted.
4. Most of the time, a contusion ring is detected surrounding the wound. Depending on its age, the ring ranges from dark crimson to bluish-black.
5. Although the dirt or wipe ring is not always visible, it is a definite evidence of an entrance wound.
6. When the shot is fired from a close range, it causes skin, flesh, or hair to scorch. When burnt skin is present, it indicates the entrance wound.
7. GSR deposits occur only from close range fire. When available, they also identify the entrance wound.
8. There is a muzzle imprint surrounding the wound.
9. The bullet may carry the GSR in its flight from ejecta, barrel fouling, and deposit on the edges or within the entry hole.
Extraneous deposits around the wound are caused by the following factors:-
1. Propellant burned powder (smoke), semi burnt and unburnt propellant.
2. Primer residue.
3. Projectile, Cartridge Case and barrel material (from fouling and bore scraping).
4. Intermediate targets.
The extent of extraneous deposit depends upon-
1. The weapon.
2. The ammunition.
3. The range.
4. The angle of fire.
5. The target characteristics.
Pink Coloration
When a shot is fired at close range or comes into contact with the skin, some carbon monoxide (generated during propellant combustion) is absorbed in the skin and flesh. It causes the skin around the wound to become pink, indicating gunshot injuries and close-range injury.
Charring, Scorching, Burning, Singeing
These are the impacts of flames or hot gases generated during propellant combustion. When a shot is fired from a close range, it causes charring. The firearm and range are distinguished by their size, shape, and extent.
Charring is frequently mistaken with Blackening, Tattooing, Dirt Ring, and even Contusion Ring. Charring is distinct from blackening. The latter may be removed using a cotton swab dampened with spirit, whilst the former cannot.
Blackening
The smoke deposits create the blackening. The smoke particles are small and light.
They do not travel long distances. As a result, smoke deposit, or blackening, is restricted to a narrow range. Smoke ranges from grey to black in black powder and from light grey to dark grey in smokeless powder..
Tattooing
Tattooing is often referred to as peppering or stippling. It is the accumulation of unburned or semi-burned powder particles beneath the skin. Tattoos, in general, cannot be removed with a swab.
Dirt Ring Or Projectile Wipe Ring
Some projectile deposits the dirt ring around the wound. The materials are sourced from-
1. The projectile may include grease. The dirt collects on the grease, which is then deposited around the incision.
2. There is a soot/GSR deposit on the bullet. The projectiles take up soot/GSR from the powder ejecta that rushes past them within or outside the barrel.
3. Dirt from an intermediate target (clothing, mud walls, etc.) or the surface from which the projectile ricocheted.
4. The pellets and buck bullets in shotgun ammo are scraped with graphite. The projectiles carry a little quantity of graphite, which they deposit around the entrance hole. Lead bullets have the potential to blacken the edges of entry wound.
Contusion
The projectile’s impact contuses the edges of the wound. Contusions range in colour from reddish dark to bluish black. The contusions generally take the shape of a ring around the wound and are of uniform width. The tissues are swelled and burst.
Exit Wound
1. They do not have a defined shape or size. They are usually bigger and more irregular than the entrance wound.
2. The exit wound is indicated by the eversion of edges and the direction of pushed or shoved out flesh.
3. The presence of a projectile that has become trapped in the exit wound.
4. If the entrance wound is formed and a probe inserted through it emerges from another incision. The latter is clearly an exit wound.
