Ballistic is the study of the motion of the projectiles and the factors affecting them. Ballistics are primarily divided into three branches internal, external and terminal ballistics. If the target is living tissue, it is known as wound ballistics.
Wound ballistics is concerned with the wounding phenomena. It studies how a projectile creates a wound and causes tissue destruction by its movements on and after entering the body, its travel and then exit from the body unless it is retained in the body.
Measurement of wound ballistic parameters gives qualitative ideas of firearm injuries inside the victim’s body.
Various Parameters of Wound Ballistics
- Entry Hole– Its inverted margin usually recognizes it, the presence of scorching, blackening, tattooing, dirt ring, size, and the number of entry holes. This helps in determining the direction from which the bullet was fired.
- Exit Hole– It is usually recognized by the absence of various marks found around the entrance wound, such as the presence of averted edges and the shape and size of the wound. They are usually larger than the entry hole and can be differentiated, and the direction can be determined.
- Bullet Track– It the distance traveled by the projectile after entering into the projectile.
- Permanent Cavity– It is caused due to the actual tissue destruction caused by bullets and depends on the cross-sectional area of the bullet.
- Temporary Cavity– Temporary nature of this cavity results from the body’s natural elasticity, which allows it to regain its original structure after the bullet has passed.
- Deposit on and inside the track of the fired target.
Methods to Measure Various Parameters of Wound Ballistics
- Gelatin blocks can be used as simulated targets, and test firing can be done. Ballistic gelatin is widely used in the study of wound ballistics. Ballistic gelatin is made up of collagen and is used as a soft tissue stimulant.
Preparation of Gelatin block involves the following procedures:
- 20 gm of gelatin powder is dissolved in 80 cc of water to prepare an aqueous solution. The solution is poured into the containers of the required size and is refrigerated overnight. Blocks of 20% gelatin at 10°C are thus ready for firing.
- Test firing is done on the simulated target by fixing the target on a rigid platform between the two sets of velocity measuring screens. The striking and the remaining velocity are measured using the velocity measurement system.
- The nature and dimensions of the entry hole and the exit hole are observed and measured using an ABFO scale.
- The permanent cavity volume is measured using a clinical graduated syringe for low-velocity projectile and graduated burette for bigger cavity volume. The various wound ballistic parameter is photographed and documented.
Another method involves using the doppler radar velocity to measure the wound ballistic parameters. The velocity of the bullet serves as the primary parameter in wound ballistics studies. The velocity of the bullets/projectiles is usually measured electronically through photoelectric barriers connected to the equipment that measures the time lapse between the impulses. This enables the velocity to be calculated.
Measurement of wound ballistics parameters such as entry hole, exit hole bullet track, temporary and permanent cavities help determine the type for the bullet used, the range of firing and also helps determine the direction from which the projectile was fired.