Terminal ballistic deals with the behavior of the missile (projectile) once it hits the target. Terminal ballistic is the study of penetration of missiles in deferent types of the target such as solids as well as liquids. It is the study of wounding capabilities in animal tissues.
It involves the studies of bullet-resistant materials such as jackets and vests. The study involves the penetration of bullets in making holes in glass panes in windows, showcases, and buildings. The target may be soil, brick, or wood.
The Terminal Ballistics may be called Wound Ballistics if the target is the human body. This is an important aspect of terminal ballistics. Since different parts of the human body react differently to similar caliber missiles with the same velocity. Broadly speaking terminal ballistics are sub-divided into penetration potential. A missile can penetrate various materials and wound ballistics which is the effect the missile has on living tissues.
The penetration of different materials could be of great value while investigating gunfire cases. To assess the performance of bullet and cartridge penetration of pine boards of various thicknesses are carried out.
The test was however been found to be of no help as it’s full of inaccuracies due to several factors mentioned below.
(i) Moisture content
(ii) Knot content
(iii) Age of the tree
(iv) Separation of boards gave variable results.
Terminal Ballistics deals with the impact of projectiles on the target as well as its working inside the target. Many targets are sent to forensic laboratories for their examination when they get involved in criminal cases after getting hit by projectiles fired from firearms resulting in injuries to them.
Targets are involved especially in cases of suicide or murder and are quite large in number.
This target can be classified into two main groups.
(i) Non Living targets
(ii) Living targets.
Non Living Targets
Non Living targets often involved in murder or suicide cases are:
(i) Window panes and glass doors
(ii) Windscreen of cars which are made of safety glass or Laminated glass
(iii) Tempered in the car side windows
(iii) Clothes become targets when a person commits suicide and fires at his chest or gets fired at his chest in murder cases.
(iv) Bulletproof vests or jackets
(v) Ricochet of bullets from surfaces of wooden and brick walls.
It can take place from the walled surface or windscreen of cars as well.
Glass is widely used for a variety of applications. In buildings, it is used for windows, in households for a variety of articles ranging from kitchen wares ornaments, bangles, and decorative pieces. It is extensively used in automobiles for headlights, and windows, etc. In a majority of the housebreaking cases, automobiles accidents, homicides hit-and-run cases, etc, glass is one of the most common forms of evidence. In all such cases, glass pieces or fragments are likely to be found on the clothes, shoes, or hair of the suspect. This is because of the backscattering of glass pieces.
Pieces of glass are found on the clothes, hair, or shoes of the victim. It is also due to the scattering effect of the impact. Sometimes during the course of police investigations, it may be of importance to determine whether a windowpane has been smashed from inside or outside and the way it has been smashed. Such circumstances arise, for example, in alleged shop breaking where investigation suggests that the allegation may be false and the theft being internal.
If it can be shown that glass alleged to have been broken by the intruders, which has been broken from the inside, the suspicions of the investigator as the truth of the allegation would be confirmed. Questions of this nature frequently arise in arson cases, insurance frauds, and faked burglaries.
Sometimes more serious cases may arise where a pane of glass may be found broken under suspicious circumstances. The task of the investigator is materially assisted if he knows what has broken the window. Pieces from the broken pane or the hole often show marks, which are characteristic of the destructive force.
Living targets can be animals or human beings especially when firearms are used for murders or suicide resulting in injuries on the body as well as inside the body. The human body or animal body is not a uniform medium. It is about 80% water in the case of human beings which is not uniformly distributed. At places, there are bones, at other places, veins, nerves, muscles, or blood places which would be making vulnerability different places.
Soft Body Armor
The forensic examiner is often doing the task, to perform the testing and evaluation of bullet-resistant vests and jackets, generally called Soft Body Armour.
History of Body Armors
Body armor, in the form of metal plates, was widely used during the time of hand- to hand combat with swords, knives, and various bludgeoning instruments. The plain steel suits were found inadequate to defeat the projectiles with the advent of the crossbow and firearm. They are rapidly becoming obsolete.
Ballistic Nylon which is a copolymer of the basic polyamide was good against shrapnel from munitions in world war second. This is used against bullets other than low-velocity soft-lead projectiles. The major advance in soft body armor came with a generation of what is loosely referred to as ‘super fibers’ which were introduced by Du- Pont.
The best known of these was a para-aramid fiber is Kevlar, which was originally used in fabric-braced radial tires. It did not take long, however, for it to be realized that it could be woven into a fabric that was so strong that it could be used in bullet-resistant, soft body amour.
The Kevlar fibers were simply woven into sheets, with variable thicknesses of yarn. The density of weave which is also called a denier provides the particular required properties. Then, the sheets were assembled into ballistics panels. They were permanently sewn into a carrier in the form of a vest.
Kevlar does produce a very effective, lightweight. It is a flexible jacket that can be tailored to stop virtually any handgun missile.
It does, however, suffer from several problems.
• It is not stable to UV light.
• It has to be kept inside a lightproof pouch.
• It is also very susceptible to attack by many household chemicals.
• It loses most of its ability to stop bullets when it is wet.
A recent development in the field of soft body armor is the use of an ultra-high molecular weight polyethylene fiber called Spectra which is produced by Allied Signal Inc. This consists of the various fine-spun fibers of polyethylene.
These fibers are laid, in dense mats, at 90 degrees to each other than covered top and bottom with a thin sheet of polyethylene. This is then heat-treated to semi-melt the fibers together or bond with a plastic resin and to form a sheet. This material must be pulled from the matrix to allow the passage of a bullet with thousands of bonded fibers. These sheets are even more efficient than Kevlar.
• This material is not affected by water.
• It is also not affected by UV light or any chemical.
• It is considerably lighter than Kevlar.
• The disadvantage of this material is that its melting point is much lower than Kevlar.
Mechanism of Bullet-Resistant Materials
The material must first deform the projectile to effectively stop the bullet. If the surface area of the bullet is large enough then the energy is transferred to the surrounding fibers. The material has adequate resistance to the passage of the bullet. A non-deformed bullet will merely push apart the weave and penetrate. The material alone will often be sufficient to cause the deformation of the bullet to be sufficiently soft, such as a plain lead bullet, semi-jacketed bullet, or a thinly jacketed bullet, etc.
If some intermediate, much more rigid material will be required to deform the bullet, the bullet is heavily jacketed or of the metal penetrating type. This generally takes the form of a hard plate which fits in front of the soft body armor.
According to the range of fire, when the bullet hits the skin at the right angle then the entrance wound has a circular appearance. In certain circumstances, however, a bullet entrance wound may be irregular in shape even though the weapon was fired at right angles. The spin which is implied to a bullet when it is fired produces a gyroscopic effect on the bullet and its motions are therefore comparable to those of a spinning top.
A bullet has a right itself and may commence wobbling again when it slows down like a spinning top. When the wobbling bullet strikes the skin surface, the entrance wound may be of an irregular shape. It resembles the injury that is produced when the skin is struck by a fragmented bullet.
The entrance wound would be usually oval when a bullet strikes the skin obliquely. It is indicative of the fact that the barrel of the gun was inclined in comparison to the surface. The direction of inclination is indicated by the property of the wound to one or other end of the burnt area.
The one end that is near the wound is the direction from which the bullet entered and the other direction to which the shot traded.
Thus if the wound is near the upper end of an oval patch of burning, its position suggests that the shot traveled from downwards. This area will also be blackened by unconsumed carbon; the blackening can be capped off with a damp rag.
Angles Smaller than Critical Angles
The projectiles may ricochet if the striking angle at the target is less than the critical angle. The comparatively soft nature of the material (lead) may, however, resist ricochet unless the angle is low enough and the surface of the target is suitable. All hard, long and curved surfaces may cause projectiles to ricochet and cause grazing.
Relative Stopping Power
Bullet performance and wounding capabilities are other subjects surrounded by myth and misinformation. In many ways, it is understandable as the number of factors how a bullet reacts on entering a human body is so diverse as to make a scientific study of the subject virtually impossible.
If the body were made uniformly from a material of constant density, it would be extremely simple to simulate the effect of a bullet, but it is not so as has been discussed, already. The results were quite interesting in that the higher-velocity small-caliber bullets, even when they had a soft or hollow point, caused no shocking power at all.
The stopping power of the bullet is proportional to the cross-sectional area of the bullet. The tests were carried out on cadavers that could not give any indication of the propensity for around to incapacitate the subject.
The smaller caliber bullets had virtually no effect on the animals at all. The 0.38″ caliber bullets had little effect until the sixth or seventh shot had been fired. Only the 0.45″ and above caliber bullets were found to have an appreciable effect, on the first shot. Firing into human cadavers and live animals are both, however, extremely sensitive subjects and are open to many adverse comments.
In an attempt to set some standard by which a bullet’s performance may be measured without shooting cadavers or animals many different materials have been used to simulate body tissue. The only medium which gave a close approximation to the effects of a bullet on human tissue is “Ballistic Gelatin”.