Dr Rajesh Purushothaman, Associate Professor, Medical College, Kozhikode, Kerala, India
Ballistics is the study of motion of projectiles. It is done under 3 headings.
- Interior ballistics- Study of motion of bullets inside the barrel of the gun.
- Exterior ballistics- Study of motion of bullets in the air once it has come out of the muzzle of the gun.
- Terminal ballistics- It is the motion or effect of projectile at the target and inside the target. Terminal ballistics is also called wound ballistics.
- Wound ballistics is the study of physiologic and medical effects of projectile weapons on humans or animals.
- It studies how projectile produces the wound and causes destruction of the tissues by its movement within the body and transfer of kinetic energy.
- Damage caused by a projectile is influenced by its design, velocity and distance.
- Any material that travels has the ability to cause injury. Its effects depend on the kinetic energy, weight, material, shape and distance travelled.
- Air resistance and barriers slows it down and gravity accelerates it. Depending on the velocity projectiles can be low velocity (under 2000feet/second) or high velocity (over 2000feet/second). Low velocity projectiles destroy tissue by crushing and high velocity projectiles damage by cavitation.
- When a projectile hits a person; it dents and compresses the skin, muscle and bone. Skin is stretched and once the elastic limit of tissue is exceeded; a hole is created and the bullet enters the body. Minimum velocity needed for penetration of skin is 40-50m/s and for bone penetration is 60m/s.
- Once the bullet is inside the body, the skin goes back to its normal state from its stretched position and the hole appears smaller than the bullet. The bullet continues to move inside the body till it goes out through the exit wound or if the energy is dissipated; it comes to lie inside the body.
Wound ballistics has the following elements;
1, Nature of target
2, Velocity of projectiles
3, Construction features of projectiles
- Wound characteristics depend on the number of projectiles, weight, deformability, expansion and fragmentation of the projectile. The organ damage depends on the wound channel size, shock wave injury, thermal injury and foreign material inside the body.
Wound ballistics help to identify;
- Whether wound is a firearm injury or not?
- Entry or exit wound?
- Postmortem or ante mortem injury?
- Fatal or not?
- Probable alleged weapon?
- Range from which the weapon was fired?
- Entry wounds are usually round or oval. They are usually smaller than the bullet causing it. Edges are inverted and are surrounded by a contusion ring.
- Dirt or wipe ring may be seen in some entry wounds. Burning of skin, singeing of hair and scorched skin can be seen with close range wounds.
- Extraneous deposits of gun powder, primer residue and projectile material can be seen. Extents of deposits depend on the gun, ammunition, range, angle of fire and target characteristics.
- Exit wounds are irregular in shape, larger than entry wounds, edges are everted. Probing can establish continuity between entry and exit wounds.
Duties of attending clinician
- In such cases, observe and record all minor and major, internal or external wounds. Describe fully the wound of entry, internal track and site of lodgment of bullet or exit wound. If possible the description should contain type of fire arm, presence or absence of extraneous deposits, direction of fire, and condition of projectile and the site of wound.
- Log all information collected through photographs, x-rays and detailed notes of findings. Preserve evidence such as clothes, projectiles, wads, extraneous deposits and charred skin pieces.
About the Author:
Dr Rajesh Purushothaman works as Associate Professor in Medical College, Kozhikode, India. In addition to his surgical skills, he has mentored a lot of undergraduate and post graduate students in Orthopaedics and teaching remains his greatest passion.
He can be contacted at drrajeshpurushothamanATyahooDOTcom