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2.17. The mechanism of the formation of traces of weapons on the bullet
Bullet marks have traditionally been investigated only for projectiles fired from a rifled firearms. In this case, the mechanism for the formation of traces is as follows.
When loading a trace of the lip of the magazine in the form of a scratch and a trace of the breech section of the chamber in the form of a worn area may remain on the cartridge pool. Both traces are practically unsuitable for weapon identification.
When fired the process of interaction between a bullet and a bore has three stages.
First stage: the bullet moves out of the barrel of the case and moves until it contacts the rifling fields. The movement is progressive and there are no marks left on the bullet.
On the second stages from the beginning of the contact of the leading part of the bullet with the rifling fields and until full penetration into them, the translational motion becomes translational-rotational. Primary traces remain on the leading surface of the bullet, which, after the end of the trace formation process, have the form of a triangular zone of parallel tracks located to the left and above the right-handed secondary traces. For left-handed rifling, the primary traces are located to the right of the secondary traces.
Third the stage begins from the moment of full penetration of the leading part of the bullet into the rifling fields and ends with the exit of the bullet from the muzzle of the bore. Passing the rifled part of the barrel, in which the rifling (and rifling fields) make a turn of 360 °, i.e. one turn, the bullet acquires progressively rotary motion and on its leading part secondary traces of rifling fields are formed. They have the character of strip-like recesses located with the same slope as the rifling in the bore. At the bottom of the traces there are traces, which display the features of the surface of the rifling fields in the area adjacent to the muzzle, and the edges of the muzzle itself. If a bullet is fired from a weapon that has a gas outlet located on the rifling field (for some Kalashnikov assault rifles), the trace from this hole remains at the bottom of the secondary trace.
As the bore wears out, the division of traces into primary and secondary becomes less clear, up to the formation of a continuous striation on the bullet, when the rifling fields are smoothed to the level of the bottom of the rifling.
2.18. Mechanism of formation of gunshot wounds
The nature of shot marks on an obstacle is influenced by: the distance of the shot, the phenomena of internal and external ballistics, the mechanical properties of the most common obstacles (glass, tin, wooden boards).
There are three typical distances in forensic ballistics:
1) point-blank (or close to point-blank);
2) within the limits of additional factors of the shot;
3) outside of this action.
In relation to a specific damage, the distance can be set in centimeters.
Internal ballistics The shot begins with the primer being pierced by the striker, which causes the explosive decomposition of the primer (initiating) composition and the flame rays through the ignition holes of the anvil of the cartridge case ignite the powder charge. After the entire powder charge ignites and the design pressure inside the cartridge is reached, the projectile begins to move under the action of powder gases along the bore. There is a wiping of the surface of the projectile on the surface of the bore. Powder gases following the projectile wash away the resulting metal particles. By the time the projectile exits the bore, a complex mixture is formed as a result of the combustion of gunpowder, collectively called "powder gases". They have high temperature(up to 2000-3000 ° C) and exert significant pressure on the walls of the bore, the bottom of the bullet and the inner surface of the bottom of the sleeve (up to 1000 atmospheres).
By the end internal ballistics shot in powder gases includes the following fractions: a) gaseous products of combustion of gunpowder; b) microscopic solid particles (the smallest clumps of burnt powders and metal flakes); c) incompletely burnt powders. At the first shot, microscopic droplets of lubrication of the barrel and cartridges are included in the powder gases.
At the moment the projectile and powder gases exit the muzzle of the barrel bore, the processes of internal ballistics end and the processes of external ballistics begin.
Processes external ballistics are traditionally considered from the point of view of the action of the main and additional factors of the shot. Under main factor a shot means the damaging effect of a projectile on an obstacle, i.e. the formation of any damage. By degree of change of a trace-perceiving object, all gunshot injuries can be divided into penetrating (with the penetration of the projectile not less than the length or diameter of the projectile) and superficial.
Penetrating injuries are divided into penetrating and blind, superficial- on tangents, ricochet marks and dents formed from a blow with an exhausted projectile.
Traces of additional shot factors must be considered in the system:
Phenomenon - Additional Shot Factors - Traces
First Appearance is the recoil of the weapon and its reflex return forward. As a result, when fired at close range or close to stop, the muzzle of the barrel (the front end of the bolt housing or barrel housing) hits the barrier, which is an additional factor in the shot. From this blow, a trace is formed on the barrier, called punch line .
Second phenomenon- expiration at high speed from the bore of powder gases. It creates a number of additional factors that are displayed through the following traces.
Mechanical impact powder gases on the barrier is displayed in the form of tears in the edges of damage resulting from the spreading of gases over the surface of the barrier. In this case, textile fabrics, felt and even dressed leather are damaged.
The next additional factor is thermal effect on the barrier. Its traces have significant variations: from slight singing of the pile of textile fabric to its charring.
An additional factor such as deposition on the barrier of substances that are part of the powder gases, is realized through three types of traces: a zone of soot deposition (coal lumps and metal particles), a zone of deposition or introduction of incompletely burned powders and a zone formed by grease spots.
Among the phenomena that give rise to additional factors of the shot include projectile surface contact with damage edges. The surface of the projectile affects the edges of the damage. This is evidenced primarily by such a trace as a wiping belt (metallization belt).
As a result of such an impact on synthetic materials (fabrics), traces of thermal nature are formed - sintering of the edges of the damage.
On the display of additional factors of the shot, i.e. The nature of the shot marks is also influenced by the physical (mainly mechanical) properties of the barrier material. Let's consider the most common of them.
Gunshot damage tree objects(boards) are largely determined by the degree of dryness (moisture) of the wood, as well as the angle at which the projectile enters the object. In a dry board with a perpendicular entry of the projectile, the inlet has a rounded shape and a diameter slightly exceeding the diameter of the leading part of the bullet. The edges of the inlet are uneven, serrated, the uneven edges are correlated with structural units - annual rings and layers of wood. The outlet usually has an irregular quadrangular shape. Its lateral sides, passing through the annual layers of wood, are quite even. The same sides that are located across these layers are uneven, jagged, with flakes and spalls.
Gunshot damage sheet metal(drainpipes, roofs, car bodies) have the shape of a funnel, tapering along the course of the projectile. The edges of the hole are shaped like the rays of an irregular star. The dimensions of the hole correspond quite accurately to the diameter of the bullet.
Gunshot damage sheet glass are characterized by a funnel-shaped or crater-shaped shape with expansion along the projectile. Radial and concentric cracks form around the damage. On the side faces of the cracks surrounding the damage, smaller cracks are formed, some ends of which are collected in a bundle, while others diverge like a panicle. At a meeting angle close to a direct one, the diameter of the damage on sheet glass corresponds quite accurately to the diameter of the bullet.
AT textile fabrics the projectile forms lesions of a rounded or quadrangular shape, depending on the structure of the tissue. The projectile destroys and carries away the fibers of the threads, and at the point of its contact with the barrier, the so-called “fabric minus” is formed, i.e. the clearance that remains when the ends of the threads come together along the edges of the damage. The ends of the threads are uneven, torn, facing into the lumen of the damage and inward, in the direction of the projectile. The dimensions of the inlet are usually somewhat smaller than the diameter of the bullet.
The same questions are put to the resolution of a forensic ballistic examination, although in order to solve them, in addition to the damage itself, it is necessary to present the weapon from which the shot was fired and similar experimental cartridges, especially to establish the distance of the shot.
Plan
Introduction
Gunshot injury
Bibliography
Introduction
Forensic medicine (English forensic pathology, German Rechtsmedizin) is a special branch of medicine that deals with the application of medical and other knowledge from the field of natural sciences for the needs of law enforcement and justice. Forensic medicine is a special medical science, a system of scientific knowledge about the patterns of occurrence, methods of detection, methods of research and evaluation of medical facts that serve as a source of evidence during the investigation provided for by law. For example, conducting forensic medical examinations helps not only to determine the cause sudden death or find the perpetrator, but also establish paternity, degree of relationship, and examine in detail any biological traces.
For writing control work I have chosen a topic ^ gunshot wound, I believe that this topic is quite relevant, because. firearms include damage caused by the energy of a burning explosive or caused by a projectile set in motion by it. A specific feature is the formation of damage by a projectile (bullet), which has a relatively small mass (grams), but a very high speed (up to 2000 m/s).
AT recent times as an independent subspecies gunshot injury began to allocate explosive injury. This term refers to damage caused by the explosion of ammunition (cartridges), explosives(gunpowder, tol, nitroglycerin, etc.) and shells (mines, grenades, air bombs, etc.).
When writing the control work, I used the following sources of literature:
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Gunshot injury
In forensic practice, the most common injuries are those caused by short-barreled or medium-barreled small arms. These weapons are extremely rare in large-caliber (10 mm or more), usually they are medium (9-7 mm) or small (6 mm or less) caliber.
The main structural element of the cartridge used in these types of weapons, which combines the powder charge, projectile (bullet) and igniter (primer) into a single whole, is the sleeve.
Sleeves for rifled medium barrel and short barreled weapons made of soft tin, coated to protect against corrosion with a film of brass or tombac. For medium-barreled weapons, they are made in the vast majority of cases in a bottle shape, for short-barreled weapons - bottle-shaped or cylindrical, depending on the design of the pistol or revolver. For smoothbore weapons sleeves are made of metal, cardboard or plastic. They are cylindrical in shape.
Cartridge. A primer containing a detonating composition is mounted in the bottom of the sleeve. The cavity of the cartridge is filled with gunpowder (fine grains or plates of nitrates, cellulose).
A projectile is placed in a free hole. For each weapon model, a specially designed cartridge is made containing a certain amount of gunpowder.
^ Projectile firearms can be in the form of a bullet (mainly for rifled weapons) or shot (for smoothbore).
Bullet can be cast entirely from lead - used for shooting from sports or hunting weapons. Bullets designed for military weapons, have different design depending on the purpose: armor-piercing, incendiary, tracer, etc. 1
The simplest design of a modern firearms bullet involves the presence of a shell (made of soft tin), a lead jacket and a core (made of tool steel). Incendiary and tracer bullets have structural elements containing a luminous compound (tracer) _ or a thermal mixture (incendiary).
Hunting and fishing carbines are supplied with cartridges filled with semi-jacketed bullets, in which the head end is not covered by a shell (in order to facilitate its deformation and fragmentation).
For smoothbore weapons, the bullet is made of lead (or brass) and can have a variety of structural shapes.
Shotguns can also be loaded with shotgun cartridges, which have a number of design differences. So, in a sleeve, gunpowder is corked first with a cardboard plate (according to the diameter of the sleeve), and then with a felt pad. These elements are called "powder wad". They serve for obturation (sealing) of the trunk. They pour on the wad fraction ( small pieces of lead - chopped or lead balls). To hold it in the cartridge, a cardboard ski is placed on top or the edges of the sleeve (folder, plastic) are rolled up. Grades of the largest fraction (with a diameter of more than 5.0 mm) were called "buckshot".
In some cases, only gunpowder can be in the cartridge (usually the barrel of the case live cartridge then rolled) or gunpowder and powder wad (in a cartridge for smoothbore weapons), the projectile itself (bullet or shot) is missing. Such cartridges are called "blank".
^ Shooting mechanism. To fire a cartridge, the cartridge is inserted into the chamber (the breech of the firearm) and closed with a bolt (or block) having a percussion mechanism. When you press the trigger (trigger), the percussion mechanism hits the primer of the cartridge, which leads to the ignition of the initiating composition of the primer, and through the seed holes (in the bottom of the sleeve) and gunpowder.
In thousandths of a second, the powder passes from a solid state to a gaseous state, and in the limited space of the sleeve, a pressure develops that reaches 400-700 atm in smooth-bore and 2000-3000 atm in rifled weapons. The projectile (bullet or shot and skis) is pushed out of the barrel of the weapon at a speed of up to 500 m / s in the case of a smooth-bore and 900-2000 m / s - rifled weapons.
When passing through the bore, a bullet in a rifled weapon, thanks to the rifling, receives a rotational movement around the longitudinal axis, which gives it stability in motion and ensures a greater flight range. Upon exiting the bore of a smooth-bore weapon, the bullet acquires a tumbling motion. Only special shellless bullets (Yakan, Breneke, Vyatka, etc.) fly without changing their position.
Immediately after the shot, the shot moves along the bore of the weapon like a compact body. However, already at the moment of exit from it, the pellets sliding along the bore (marginal) begin to deviate and after 1-4 m (depending on the type of drilling of the barrel) can form isolated damage in the barrier around the main damage formed by the compact mass of shot. During the flight, the shot is scattered more and more (Fig. 9).
In the process of moving along the bore, the projectile pushes out the air in it, which "flows" from the barrel at the speed of the projectile (the so-called pre-bullet air). Having a significant speed, such a jet of air at a close distance (several centimeters) is capable of causing significant damage. So, when fired at close range, the pre-bullet air in the barrier (clothes, skin) knocks out a hole corresponding to the muzzle of the weapon. At a distance of 3-5 cm, it can form a kind of "bruise zone" in the form. rings (or two symmetrical rings) around the skin wound - air ring.
Following the projectile, the gases of the shot escape from the bore of the weapon - combustion products of the initiating composition of the primer and gunpowder, containing soot, half-burned and unburned powders, metal dust from the friction of the projectile against the bore and lubricant, the so-called additional factors or related components of the shot. 2
Possessing a speed much higher than the speed of the projectile, they immediately overtake it in flight. Thus, for some time he flies as if in a cloud of shot gases. However, after a few tens of centimeters (depending on the type of weapon), the accompanying components of the shot lose their speed, and the projectile already overtakes them. (see Appendix No. 1 of the test)
After 3-7 m, cardboard (shot) wads lose speed, and then (up to 30 m) and powder ones. Only a projectile flies over a long distance (shot - several hundred meters, bullets - more than a kilometer). Thus, all components of the shot (pre-bullet air, wads, products of the shot and the projectile), depending on their mass, fly at different distances.
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The mechanism of formation of gunshot damage
The following elements can be distinguished in the structure of gunshot damage.
Entry gunshot wound. The moment a projectile hits an obstacle, it is accompanied by a whole range of mechanical effects. First of all, it generates the spread of kinetic energy in the direction of the bullet's movement - shock head wave the speed of which approaches the speed of sound propagation in a given medium (in human soft tissues it is 1740 m/s).
Having a speed greater than the speed of the projectile, the shock bow wave acts on soft tissues that have not yet been damaged, causing them to form molecular shock zones. Subsequently (if the victim remains alive), the tissues corresponding to this area become necrotic, so the actual amount of damage is much larger than the area itself. wound channel. The effect of the formation of a shock head wave also explains the formation of damage to soft tissues and bones far (outside the zone) of the passage of the wound channel.
The surface of the projectile is always contaminated to some extent. When introduced into the barrier, the pollution, rubbing against the edges of the wound, is superimposed on the belt of deposition in the form of a "rubbing belt", less often it goes beyond its limits. The composition of the rubdown belt includes soot, grease and metal. In this way, hallmarks the entrance gunshot wounds are a tissue defect ("minus"-tissue), a belt of rawness and a belt of rubbing.
wound channel. Penetrating into the barrier, the projectile forms a wound channel, causing a kind of pulsating oscillations of the wall in a direction transverse to the channel. Encountering an obstacle on its way (for example, a bone), the projectile can ricochet and change its direction, forming a broken wound channel. Passing through cavities or several parts of the body (for example, the shoulder-thorax), it can form a so-called interrupted wound channel.
Damage to a flat bone, the projectile forms a through hole in it in the form of a truncated cone. Its base faces the direction of the projectile, and the smaller diameter roughly corresponds to its caliber. When long tubular bones are damaged, predominantly radial cracks are formed in the projectile entry zone, and longitudinal cracks are formed at the exit site.
If the projectile damages a hollow organ containing fluid (for example, an overflowing bladder, the stomach filled with food, the heart during diastole), then the liquid, receiving kinetic energy due to the shock head wave, destroys the walls of the organ before they are hit by a projectile.
At a significant speed, passing near the bone, the projectile can form its fracture, morphologically similar to damage by a blunt object.
In rare cases, when a projectile gets stuck in the barrel when fired (poor-quality gunpowder), it can be ejected on a subsequent shot. When hit at a distance of several meters from such a "double" projectile, one gunshot wound is formed. In the wound channel, these projectiles are separated, and each of them separately forms further its own wound channel.
Exit gunshot wound. It is formed in those cases when the kinetic energy of the injuring projectile is sufficient to form a through wound channel. In the event of a bullet through the bullet in the process of its further flight, it can cause other damage, including the injury of another person.
Having reached the skin at the exit, the bullet, as it were, protrudes and stretches the skin, which is torn at the same time. The resulting exit gunshot wound has a slit-like shape. Quite often, its edges seem to be turned inside out. As a rule, they are uneven, but match when compared.
The exit gunshot wound does not have a defect in the tissue, belts of aggravation and wiping. Accordingly, there are no deposits of soot, powders and no metallization on the skin around it. Only in some cases, when the exit gunshot wound is formed in places where a dense object is pressed against the skin (dense coarse clothing, a belt, etc.), conditions arise for traumatizing the skin around the exit wound. The protruding area of the skin seems to be squeezed and bent between solid objects (for example, a belt and the head of a bullet). There is a bruised area of a round or oval shape, which. after drying, the skin may resemble a belt of sedimentation.
^ Features of gunshot wounds depending on the type of shells that caused them. Wounds inflicted special purpose bullets tracer, incendiary, etc.), in principle, are no different from ordinary bullet wounds, except for those cases when the wound is blind, and the pyrotechnic composition of the bullet continues to burn. In these cases, there are thermal lesions of the wound channel.
Damage from automatic weapons when firing a burst differ in their location: the entrance gunshot wounds are located on the same side of the body, have a similar direction and are located relatively close to each other. 3
^ Setting the shot distance . Depending on the distance at which the muzzle of the weapon is from the obstacle, it will be affected by all the components of the shot, part of them, or only the projectile.
Under point-blank shot imply such gunshot damage when the muzzle of the weapon at the time of the shot is tightly pressed against the barrier (clothing, skin). In this case, in accordance with the muzzle hole, the pre-bullet air knocks out a defect (hole) in it, into which the bullet enters, sliding along the side surface along the edges of the wound. Together with the bullet that forms the wound channel, the gases of the shot burst into it. Having a lot of pressure, they usually tear clothes crosswise, peel off the skin around the wound and, pressing it sharply against the cut of the weapon's barrel, form its imprint on it - a "punching mark".
For some weapon systems (submachine guns) that have a muzzle brake-compensator, it is impossible to fire at point-blank range. If the weapon is pressed against the barrier, it will not be the muzzle of the barrel that will rest against it, but the casing of the compensator brake. In such a situation, the deposition of soot from the shot is characteristic in accordance with the windows in the compensator. Since the gap between the muzzle brake and the obstacle is small (1-3 cm), a cruciform tissue rupture occurs due to the action of powder gases.
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Features of the inspection of the scene
When examining the scene great importance acquire both the examination of the corpse itself and the search for specific material evidence. Carefully fix the position and posture of the corpse, the presence (or absence) of weapons, ammunition, spent cartridges, bullets, shot, wads. All this is recorded with an exact indication of the distance and location of the material evidence found in relation to the corpse and its parts.
On the weapon, especially on the bore, one can detect soot, traces of blood, particles of tissues and organs. Puddles and streaks of blood, drops and their location, direction and shape of splashes on surrounding objects are noted. The position of the corpse is compared with the features of traces of blood.
The clothes are examined in detail, on which the presence (or absence) of blood and the direction of its streaks are also noted. Their comparison helps in determining the position of the body at the time of injury.
On the clothes and the body of the corpse, the presence of input and output injuries is ascertained with the obligatory characteristic of their typical signs. Roughly determine the direction of the wound channel, taking into account the localization of the input and output gunshot wounds and the location of the bullet, if it is detected. With blind and multiple gunshot. injuries, it is possible to judge the direction of the wound channel only by the results of the autopsy of the corpse. Determine the distance from which the shot was fired (according to the features of its traces around inlet on clothes and skin). At the same time, it is sometimes possible to express an opinion about the type of weapon, judging by the nature of the soot deposits, the shape of the stamp, etc.
At the scene of the incident, it is strictly forbidden to wash or wipe the inlet and outlet, any kind of probing of the wound channel, extracting bullets, wads, bone fragments, etc. from wounds. Loose bullets, skis found in folds of clothing should be seized for forensic ballistic examination.
In the direction of the wound channel, in some cases, one can judge the posture and relative position of the shooter and the victim, as well as the possibility of firing a shot with one's own hand. The posture of the victim can be restored in an investigative experiment on the basis of investigative and expert data, as well as the nature of the combination of injuries to several areas of the body with one bullet. The direction of the shot at an angle of less than 90° is determined by the shape and nature of the impregnation (introduction) of the components of the shot around the entrance gunshot wound, as well as by the uneven severity of the belt.
The fact that a shot was fired by a specific person can be established by detecting the deposition of shot soot and particles of gunpowder on the clothes, skin (face, hands) and in the nasal cavity of the shooter.
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Issues resolved during the examination of gunshot injuries
1. At what distance was the shot fired?
The distance of the shot is the distance from the muzzle of the weapon facing the barrier to the inlet on it. The solution of this issue, along with other investigative and expert data, allows the investigating authorities and the court to establish the nature of the incident (murder, suicide, accident). The distance of the shot can be determined up to 3.5-5 m, i.e. if there are deposits of PWV on clothing or in the circumference of the entry wound. "More or less precise definition shot distances are produced only by experimental firing from the same weapon with its cartridges of the same batch as passing through this case. Moreover, for clothing, the same material is used, which consists of the damaged item of clothing presented for research. (Annex 2)
Sometimes, with bullet damage, the picture in the area of the inlet when fired outside the scope of the "SPV" can imitate the presence of "SPV" and, therefore, be the cause blunders when determining the distance of the shot. In particular, this happens when damaged by ricocheted bullets. On clothes and the body, located at a distance of up to 2 m from the place of the rebound, there are peculiar injuries. The inlet is usually irregularly shaped or multiple inlets are formed. Sometimes the appearance of the inlet to the eye turns out to be indistinguishable from the inlet with a close shot for a special purpose is determined based on the study of its fragments.
^ 2. What is the direction of the bullet channel in the body and clothes (determination of the inlet and outlet)?
This is necessary to find out the relative position of the shooter and the victim at the time of the shot, the place from which the shot was fired, as well as to obtain data to resolve the issue of the type of death (murder, suicide, accident), since information about the localization of the inlet often allows exclude the possibility of a shot with his own hand.
When establishing the direction of the bullet channel, they first find out from which side the bullet flew, and then at what angle it burned through the clothes and body.
Determining from which side the bullet flew, with through damage, usually comes down to identifying the exit hole in the course of that. With this, it is understood that the bullet in the body and clothing on the segment between the inlet and outlet flies in a straight line. However, the so-called girdle wounds are also known. Internal ricochets are possible when the bullet, hitting the hard tissues of the body (bones), changes the direction of its movement. In multi-layer clothing, a bullet can change its direction of movement before hitting a button, buckle, etc. Therefore, to determine the direction of the bullet's flight, it is necessary to establish whether the bullet channel connecting these holes is straight.
In practice, the conclusions of the expert are usually limited to general indications, for example, they distinguish that the shot was fired from left to right at such and such an angle (indicating degrees), somewhat from top to bottom and from front to back. An experimental reproduction of the pose in which the damage was inflicted is also carried out.
Definition input holes is not difficult in the presence of "SPV". In the absence of "SPV", in order to distinguish the inlet from the outlet, they are guided by a number of signs that can only be found at the inlet, as well as comparing the studied holes with each other in size, shape, etc.
^ 3. What is the type and model of the weapon from which the victim was shot?
Determination of the type and model of weapons on the grounds of gunshot damage is possible only in individual cases. Thus, multiple small inlets of the same type are characteristic of shot damage (shotguns).
The most important for the definition are the features of "SPV" in the area of the inlet. The necessary data can sometimes be obtained from the diameter of the wiping rim of the entrance hole (in some cases it corresponds to the caliber of the bullet that struck this hole), from the characteristic shape of the entrance hole, as well as from traces of metal on the edges of the entrance hole and in the bullet channel. With multiple bullet injuries, the nature of the relative position of the inlets is used to solve this issue. Finally, some information about the type of weapon can sometimes be obtained on the basis of the amount of penetration of a bullet.
^ 4. How many bullets did damage?
The easiest way to determine the number of bullets that caused damage to the body of clothing, when all wounds are blind. The number of inlet holes in this case correspond to the number of bullets that inflicted them, and the bullets themselves are found in the depth of the bullet channels.
In case of through damage, to resolve this issue, the number of inlet and outlet holes is set, since each pair, consisting of an inlet and an outlet located on the opposite side, is usually applied by one bullet. However, there are often difficulties. Fewer entry holes than the number of bullets that caused damage,
Occasionally observed when firing automatic bursts from a tightly fixed machine gun. At the same time, even at shot distances of 100 and 150 cm, one inlet is formed, however, it is larger in size than from a single shot. With contact shots from machine guns, the formation of one inlet in a queue of two or three shots is common.
When fired, the bullet may meet in the bore another bullet, stuck from the previous shot, and knock it out, both of which will inflict the same entrance hole. This is observed, for example, when firing pistols with defective cartridges.
^ 5. What is the damage sequence?
The ability to determine the sequence of wounds is limited. For this purpose, a number of features are used, including deposits of gun grease.
After cleaning, the barrel bore of the weapon is covered with a special grease consisting of mineral oils. When fired, the bullet carries away some of this lubricant on its surface. The latter is deposited along the edges of the inlet and is used to determine the sequence of shots. However, gun grease in the inlet wiping rim can be detected not only during the first shot after the channel has been lubricated, but also after the second or third shot. For this purpose, a comparative study of the color and intensity of the luminescence of the extracts obtained with the help of ether from the clothing fabric and the standards of the standard luminescent scale is carried out. Such a scale is made up of various dilutions of gun grease in ether. To determine the sequence of infliction of injuries, the features of the injuries themselves are also used.
So, with multiple head wounds on the skull around the inlet and outlet holes of the first wound, large radial cracks are formed, interconnected by arcuate cracks, which can be located in two or three rows at different distances from the edge of the hole. At the same time, at the edges of the holes of subsequent wounds, mainly only radial cracks are formed, and segmental fragments, typical for the edges of the first holes, are not formed.
With multiple chest wounds, differences in the nature of the bullet channels are used. The first wound channel in the lung due to the fall of the lung tissue is displaced upward in relation to the segments of the same wound channel in the chest wall. In subsequent injuries, when the lung has already fallen asleep, it is not damaged at all if the bullet channels pass through its peripheral sections, and the entire passage through chest the channel does not have a stepped appearance, as from the first bullet, but is strictly rectilinear. There is another difference. At the first injury, a more extensive wound channel is formed in the lung than at subsequent injuries, when an already collapsed lung is affected.
In case of abdominal wounds, primary penetrating abdominal cavity injuries are accompanied by extensive ruptures of the intestines of the stomach. In contrast, with secondary wounds, the openings in the walls of the genital organs and abdomen are small.
^ 6. What was it like mutual arrangement weapons and the body of the victim when fired?
Determining the relative position of the weapon and the body of the victim at the time of the shot is of great interest to the judicial and investigative authorities, as it allows one to judge the posture of the shooter and the victim (in most cases it is possible to establish the degree of inclination of the weapon barrel in relation to the surface of the body and clothing, and in some cases and the position of the surfaces of the weapon in relation to the surface of the body and clothing, for example, to determine that the barrel of the weapon was not only tilted to one side, but was also located with its front sight in a certain direction).
As practice shows, the relative position of the weapon and the body can be established only in individual cases. For this purpose, the direction of the bullet channel, the nature of the location of the "SPV" around the inlet, the shape of the rim of the bullet wipe are used. Sometimes the necessary data can be obtained on the basis of studying the features of the imprint of the muzzle end of the weapon, when shot with shot - the shape of the shot scree on the barrier.
^
Bibliography
1. Samishchenko S.S. Forensic Medicine. Textbook for law schools. 2006
2. Forensic medicine. V.L. Popov. Forensic medicine in questions and answers V.I. Akopov. 2000
3. Forensic medicine. Lectures for non-core listeners.
4. Avdeev M.I., Course of forensic medicine, M., 1959;
5. Gromov A.P., Course of lectures on forensic medicine, M., 1970.
The mechanism of the formation of traces of weapons on the bullet
Bullet marks have traditionally been examined only for projectiles fired from rifled firearms. In this case, the mechanism for the formation of traces is as follows.
When loading a trace of the lip of the magazine in the form of a scratch and a trace of the breech section of the chamber in the form of a worn area may remain on the cartridge pool. Both traces are practically unsuitable for weapon identification.
When fired the process of interaction between a bullet and a bore has three stages.
First stage: the bullet moves out of the barrel of the case and moves until it contacts the rifling fields. The movement is progressive and there are no marks left on the bullet.
On the second stages from the beginning of the contact of the leading part of the bullet with the rifling fields and until full penetration into them, the translational motion becomes translational-rotational. Primary traces remain on the leading surface of the bullet, which, after the end of the trace formation process, have the form of a triangular zone of parallel tracks located to the left and above the right-handed secondary traces. For left-handed rifling, the primary traces are located to the right of the secondary traces.
Third the stage begins from the moment of full penetration of the leading part of the bullet into the rifling fields and ends with the exit of the bullet from the muzzle of the bore. Passing the rifled part of the barrel, in which the rifling (and rifling fields) make a turn of 360 °, i.e. one revolution, the bullet acquires a translational-rotational motion and secondary traces of rifling fields form on its leading part. They have the character of strip-like recesses located with the same slope as the rifling in the bore. At the bottom of the traces there are traces, which display the features of the surface of the rifling fields in the area adjacent to the muzzle, and the edges of the muzzle itself. If a bullet is fired from a weapon that has a gas outlet located on the rifling field (for some Kalashnikov assault rifles), the trace from this hole remains at the bottom of the secondary trace.
As the bore wears out, the division of traces into primary and secondary becomes less clear, up to the formation of a continuous striation on the bullet, when the rifling fields are smoothed to the level of the bottom of the rifling.
The nature of shot marks on an obstacle is influenced by: the distance of the shot, the phenomena of internal and external ballistics, the mechanical properties of the most common obstacles (glass, tin, wooden boards).
There are three typical distances in forensic ballistics:
1) point-blank (or close to point-blank);
2) within the limits of additional factors of the shot;
3) outside of this action.
In relation to a specific damage, the distance can be set in centimeters.
Internal ballistics The shot begins with the primer being pierced by the striker, which causes the explosive decomposition of the primer (initiating) composition and the flame rays through the ignition holes of the anvil of the cartridge case ignite the powder charge. After the entire powder charge ignites and the design pressure inside the cartridge is reached, the projectile begins to move under the action of powder gases along the bore. There is a wiping of the surface of the projectile on the surface of the bore. Powder gases following the projectile wash away the resulting metal particles. By the time the projectile exits the bore, a complex mixture is formed as a result of the combustion of gunpowder, collectively called "powder gases". They have a high temperature (up to 2000-3000 ° C) and exert significant pressure on the walls of the bore, the bottom of the bullet and the inner surface of the bottom of the sleeve (up to 1000 atmospheres).
By the end of the internal ballistics of the shot, the powder gases include the following fractions: a) gaseous products of the combustion of gunpowder; b) microscopic solid particles (the smallest clumps of burnt powders and metal flakes); c) incompletely burnt powders. At the first shot, microscopic droplets of lubrication of the barrel and cartridges are included in the powder gases.
At the moment the projectile and powder gases exit the muzzle of the barrel bore, the processes of internal ballistics end and the processes of external ballistics begin.
Processes external ballistics are traditionally considered from the point of view of the action of the main and additional factors of the shot. Under main factor a shot means the damaging effect of a projectile on an obstacle, i.e. the formation of any damage. By degree of change of a trace-perceiving object, all gunshot injuries can be divided into penetrating (with the penetration of the projectile not less than the length or diameter of the projectile) and superficial.
Penetrating injuries are divided into penetrating and blind, superficial- on tangents, ricochet marks and dents formed from a blow with an exhausted projectile.
Traces of additional shot factors must be considered in the system:
Phenomenon - Additional Shot Factors - Traces
First Appearance is the recoil of the weapon and its reflex return forward. As a result, when fired at close range or close to stop, the muzzle of the barrel (the front end of the bolt housing or barrel housing) hits the barrier, which is an additional factor in the shot. From this blow, a trace is formed on the barrier, called punch line .
Second phenomenon- expiration at high speed from the bore of powder gases. It creates a number of additional factors that are displayed through the following traces.
Mechanical impact powder gases on the barrier is displayed in the form of tears in the edges of damage resulting from the spreading of gases over the surface of the barrier. In this case, textile fabrics, felt and even dressed leather are damaged.
The next additional factor is thermal effect on the barrier. Its traces have significant variations: from slight singing of the pile of textile fabric to its charring.
An additional factor such as deposition on the barrier of substances that are part of the powder gases, is realized through three types of traces: a zone of soot deposition (coal lumps and metal particles), a zone of deposition or introduction of incompletely burned powders and a zone formed by grease spots.
Among the phenomena that give rise to additional factors of the shot include projectile surface contact with damage edges. The surface of the projectile affects the edges of the damage. This is evidenced primarily by such a trace as a wiping belt (metallization belt).
As a result of such an impact on synthetic materials (fabrics), traces of thermal nature are formed - sintering of the edges of the damage.
On the display of additional factors of the shot, i.e. The nature of the shot marks is also influenced by the physical (mainly mechanical) properties of the barrier material. Let's consider the most common of them.
Gunshot damage tree objects(boards) are largely determined by the degree of dryness (moisture) of the wood, as well as the angle at which the projectile enters the object. In a dry board with a perpendicular entry of the projectile, the inlet has a rounded shape and a diameter slightly exceeding the diameter of the leading part of the bullet. The edges of the inlet are uneven, serrated, the uneven edges are correlated with structural units - annual rings and layers of wood. The outlet usually has an irregular quadrangular shape. Its lateral sides, passing through the annual layers of wood, are quite even. The same sides that are located across these layers are uneven, jagged, with flakes and spalls.
Gunshot damage sheet metal(drainpipes, roofs, car bodies) have the shape of a funnel, tapering along the course of the projectile. The edges of the hole are shaped like the rays of an irregular star. The dimensions of the hole correspond quite accurately to the diameter of the bullet.
Gunshot damage sheet glass are characterized by a funnel-shaped or crater-shaped shape with expansion along the projectile. Radial and concentric cracks form around the damage. On the side faces of the cracks surrounding the damage, smaller cracks are formed, some ends of which are collected in a bundle, while others diverge like a panicle. At a meeting angle close to a direct one, the diameter of the damage on sheet glass corresponds quite accurately to the diameter of the bullet.
AT textile fabrics the projectile forms lesions of a rounded or quadrangular shape, depending on the structure of the tissue. The projectile destroys and carries away the fibers of the threads, and at the point of its contact with the barrier, the so-called “fabric minus” is formed, i.e. the clearance that remains when the ends of the threads come together along the edges of the damage. The ends of the threads are uneven, torn, facing into the lumen of the damage and inward, in the direction of the projectile. The dimensions of the inlet are usually somewhat smaller than the diameter of the bullet.
The same questions are put to the resolution of a forensic ballistic examination, although in order to solve them, in addition to the damage itself, it is necessary to present the weapon from which the shot was fired and similar experimental cartridges, especially to establish the distance of the shot.
It is generally accepted that the terms "gunshot wound mechanism" and "wound ballistics" have an equal right to exist and carry an equivalent meaning. They determine the process of interaction of a firearm with the affected biological tissues of the body, which occurs under the influence of both conditions environment, and the properties of the whole organism.
An outstanding contribution to the doctrine of a gunshot wound was made by domestic scientists-surgeons N.I. Pirogov, V.A. Oppel, E.V. Pavlov, S.S. Girgolav, A.N. Maksimenkov, I.S. Kolesnikov, E.A. Dyskin, M.I. Lytkin and others.
It has long been noted that the gunshot wound has significant distinctive features. First of all, this was expressed in a severe general reaction of the body to injury, difficulties in treating such injuries, and frequent complications of purulent and putrefactive processes.
Throughout history, various theories have been created to explain the more severe course of gunshot wounds. So, Vigo suggested that the gunshot wound was poisoned by particles of gunpowder brought along with the bullet. Since the bullet heated up in the bore and in flight during firing, the burn theory was proposed. Melzens proposed the theory of "air concussion", based on the fact that air penetrating with a wounding projectile causes major tissue damage. Theories of incorrect rotation (Vogel) and deformation (Bruns, Delorme) were proposed. The founders of the theory of hydraulic action were the German scientists Kocher, Bruns, Bush. They suggested that when a bullet penetrates the tissue in the latter, according to Pascal's law, conditions arise similar to the action of a hydraulic press. Subsequently, the hydrodynamic theory (Schörning, Koller) and the theory of impact action (V.A. Thiele) were formulated, which in general have retained their significance to this day.
Modern ideas about the mechanism of the occurrence of a gunshot wound are mainly limited to the theory of direct and side impact. The main role is assigned to four influencing factors: 1 - head shock wave; 2 - wounding projectile; 3 - side impact energy; 4 - vortex wake.
Morphological and functional changes that occur in the wound are associated not only with the direct impact of the injuring projectile, but also with damage to adjacent tissues, often significantly removed from the wound channel. The phenomenon of side impact is the most important feature of a gunshot wound, which determines the extent of damage outside the wound channel. The energy absorbed by the tissues is transformed in this case into the energy of particles moving away from the wound channel, forming a rarefaction site and a temporary pulsating cavity. With the help of high-speed filming, phenomena occurring in transparent objects in the form of rectangular blocks of 20 gelatin during the passage of a wounding projectile were recorded and studied. It was revealed that a firearm, forming a hydrodynamic wave, sharply throws the elements of a dense medium forward and radially in all directions. At the same time, a zone of rarefaction is formed in the tissues behind the bullet, which is replaced by a zone of increased pressure within a short period of time. Thus, a temporary pulsating cavity (VPP) is formed, and the process itself is called "cavitation". It has been established that the runway is formed under the influence of a firearm having a velocity value in the range of 214-990 m/s, and its maximum size when injured by high-speed firearms is 20–40 times greater than the diameter of the bullet. The time of existence of a pulsating cavity can be tens and even hundreds of times longer than the time of passage of a bullet through an object. The dimensions of the cavity, the duration and number of pulsations, the amount of pressure on the surrounding tissues and, accordingly, the degree of tissue damage depend on the amount of energy absorbed by them. This effect explains tissue damage far beyond the wound channel.
Rice. 18. Zones of a gunshot wound:
I - zone of the wound channel, II - zone of primary necrosis, III - zone of contusion (a - with irreversible changes, b - with reversible changes).
The impact on the tissues of the force of a side impact is also determined by the formation of the so-called zones of a gunshot wound (Fig. 18). The classical concepts of Borst (1917) about the existence of three zones of injury in a gunshot wound, namely, the wound channel, the zone of primary traumatic necrosis and the zone of molecular concussion have retained their relevance to the present. It should be noted that the priority in the use of the term "molecular shaking" belongs to N.I. Pirogov, who, back in 1848, wrote in his monograph "The Beginnings of General Military Field Surgery": its limits and extent we are never able to determine precisely.
As a result of a gunshot wound, a tissue defect is formed - a wound channel, which is usually designated as zone I of a gunshot wound. In most cases, the wound channel is a slit-like cavity, closed as a result of tissue displacement and edema. It is filled with wound detritus, blood, foreign bodies. The movement of a bullet in tissues is not always straightforward, especially at the interface between media of different densities. Such a deviation from the rectilinear movement is called the primary deviation of the wound channel. At a later date, a further change in the configuration of the wound channel (secondary deviation) may occur due to different contractility of tissues, the occurrence of hematomas, the development of edema, and a change in the position of the limb after injury. Along with the impact of secondary wounding projectiles, deviation often leads to large defects in biological tissues with significant the number of pockets and gaps.
Rice. 19. Gunshot bullet wounds of soft tissues from AK-47:
a) the inlet of the zygomatic region on the right; b) outlet in the suprascapular region on the left.
With a through wound, the wound channel has two openings: an inlet and an outlet (Fig. 19), with a blind wound, only an inlet, and at the blind end of the wound channel there is a wounding projectile. The direction and shape of the wound channel depend on the speed of the injuring projectile, on the amount of tissue resistance, and on the angle at which the projectile meets the obstacle. Figure 20 shows the wound channels for stable and unstable bullet flight.
Rice. 20. The shape of the wound channel during the unstable and stable flight of the bullet.
The zone of necrotic tissue, which is formed in a gunshot wound as a result of a direct blow, is commonly called the zone of primary necrosis (II). Directly adjacent to this area are tissues in which changes are less pronounced, and the degree of viability impairment is very different. The formation and subsequent formation of this zone (III), which was assigned the terms "contusion zone", "side impact zone", "molecular shaking zone", are determined by many factors acting at the time of injury and after it. Tissues assigned to zone III can be conditionally divided into tissues with irreversible changes (IIIa), in which late (or secondary) necrosis is subsequently formed, and tissues with reversible changes, the viability of which is subsequently restored (IIIb). The architectonics of a gunshot wound is complex. Despite the decrease in the severity of necrodystrophic changes towards the periphery of the wound channel, tissues with different levels of viability may coexist in different areas. The zone of secondary changes is never presented as a continuous array, but has a focal, mosaic character. It should be remembered that the changes occurring in the tissues of this area are reversible with rationally chosen treatment, but can lead to tissue death with the formation and expansion of a zone of secondary necrosis, the development of purulent and other complications of the wound process with incorrectly chosen treatment tactics or delayed treatment.
In the near future after the injury, significant changes in physicochemical processes develop in the tissues surrounding the gunshot wound, a sharp depression of tissue respiration, pronounced changes in the microcirculatory bed in the form of spasm of arterioles and precapillaries, expansion of venules and opening of arteriolo-venular shunts. Metabolic acidosis and tissue edema develop, which is a response of the body to a strong traumatic effect. In turn, tissue edema significantly impairs the microcirculation of injured tissues.
Modern wound ballistics defines a gunshot wound as a complex process of interaction between a wounding projectile and a damaged biological object. The nature of the gunshot injury depends on many factors that can be summarized in three groups: the properties of the firearm (mass, shape, caliber, length, design features), the features of the movement of the bullet in the air (speed, stability) and the properties of the affected tissues.
The nature of the gunshot wound, first of all, depends on the kinetic energy of the injuring projectile, which is determined by the speed and mass, which follows from the formula E \u003d mv 2 /2. All firearm wounding projectiles can cause low-energy and high-energy effects on biological tissues.
However, the same weapon under different conditions can cause different damage. In the process of flight, in addition to the translational movement, the bullet makes a number of other movements. Most handguns have helical rifling for gyroscopic stabilization on an external ballistic trajectory, so the bullet acquires rotational motion at a frequency of up to 3000 rpm. In this case, the head end of the bullet performs rotational (precession) and oscillatory (nutation) movements relative to the axis of the trajectory due to the action of aerodynamic forces. The deviation of the injuring projectile from the longitudinal axis of the flight path creates the so-called "yaw angle", depending on which the bullet can enter the object at a greater or lesser angle, which causes different stability at the moment of injury.
The mass, shape, caliber and design features of the bullet affect the nature of the wound. These indicators are interrelated and are evaluated in relation to a particular type of weapon. So, bullets with a large mass, length and caliber are considered the most stable. Short 9 mm blunt bullets for the Makarov pistol (m = 6.1 g) quickly transfer energy to the tissues, forming blind wounds with the so-called "stopping effect". At the same time, pointed elongated shell bullets of 7.62 mm caliber with a mass of 7.9 g often give only one tenth of their kinetic energy, forming penetrating wounds with small inlet and outlet holes.
Other design features are also essential, such as the presence of shells, a core, and the position of the center of gravity in the bullet. Currently, only jacketed bullets are used in military weapons. Jacketless bullets, as the most easily deformable and dangerous, are prohibited by the Hague Convention of 1899. The destruction, fragmentation or, as they say, "dismantling" of the bullet at the time of injury contributes to causing more severe and extensive damage.
Shifting the center of gravity to the tail of the bullet is one way to increase the lethal force of the weapon. As a result of the interaction of such a bullet with a dense barrier, the bullet overturns, followed by somersaulting and transferring significantly more energy to biological tissues than during stable flight.
The unstable movement of a bullet in the body is predetermined not only by its design features, but also by the features of external ballistics, among which speed should be considered first of all. The higher the speed of the bullet, the greater its ability to give kinetic energy to the tissues. This is especially true for small-caliber bullets (5.45 mm from AK-74 and 5.56 mm from M-16-A-1). At speeds above 900 m / s, such bullets often break down in the tissues, giving them all the energy they have. In this case, massive damage occurs in the area of the inlet.
With modern combat with infantry weapons, the usual range of aimed fire is 100-150 m. The striking elements with very high energy fall into the same range. To the same damaging factors one can also include injuring shells in the form of fragments of mines, grenades, bombs, rockets flying at a speed of up to 2000 m / s. Possessing an aerodynamically unfavorable shape, albeit of an insignificant weight, carrying colossal energy, they create a potential danger in the formation of severe damage to biological structures. Modern tendencies in the development of fragmentation ammunition lie in the field of creating mines, bombs, shells stuffed with standard damaging elements (balls, needle and arrow-shaped bullets, ribbed cubes, etc.). In addition, quite often, injuries resulting from the explosion of mines, grenades, shells and bombs are combined with local and general impact of the shock wave. As a result, closed injuries may occur, aggravating the course of a gunshot injury.
When the flight speed of the wounding element is more than 1300-1500 m / s. the inlet becomes larger than the outlet and is 6-8 times the diameter of the bullet. Such supersonic wounding projectiles, when they hit the target, cause a “transonic flow”, which has such a steep front and powerful shock waves that they seem to break out or “jump out” of the wound channel, tearing out biological tissues. A funnel of destroyed and necrotic structures is formed on the surface, that is, the contour of a temporary pulsating cavity leaves the zone of the wound channel through the inlet, making it unreasonably large and creating a wound with its base facing the inlet. Such wounds in the English-language literature are called "shark bite" - a shark bite.
Different biological structures react differently to the phenomenon of cavitation. The main carriers of the cavitation effect are tissues containing a significant amount of water. Parenchymal organs and muscles are especially susceptible to it. Lung tissue is less significantly injured. Hollow organs are torn due to compressive and decompressive waves of a temporary pulsating cavity, while the zones of necrosis are insignificant.
Thus, the nature of combat damage due to the use of firearms in terms of wound ballistics can be represented as follows (Fig. 21).
The nature of shot marks on an obstacle is influenced by: the distance of the shot, the phenomena of internal and external ballistics, the mechanical properties of the most common obstacles (glass, tin, wooden boards).
There are three typical distances in forensic ballistics:
1) point-blank (or close to point-blank);
2) within the limits of additional factors of the shot;
3) outside of this action.
In relation to a specific damage, the distance can be set in centimeters.
Internal ballistics The shot begins with the primer being pierced by the striker, which causes the explosive decomposition of the primer (initiating) composition and the flame rays through the ignition holes of the anvil of the cartridge case ignite the powder charge. After the entire powder charge ignites and the design pressure inside the cartridge is reached, the projectile begins to move under the action of powder gases along the bore. There is a wiping of the surface of the projectile on the surface of the bore. Powder gases following the projectile wash away the resulting metal particles. By the time the projectile exits the bore, a complex mixture is formed as a result of the combustion of gunpowder, collectively called "powder gases". They have a high temperature (up to 2000-3000 ° C) and exert significant pressure on the walls of the bore, the bottom of the bullet and the inner surface of the bottom of the sleeve (up to 1000 atmospheres).
By the end of the internal ballistics of the shot, the powder gases include the following fractions: a) gaseous products of the combustion of gunpowder; b) microscopic solid particles (the smallest clumps of burnt powders and metal flakes); c) incompletely burnt powders. At the first shot, microscopic droplets of lubrication of the barrel and cartridges are included in the powder gases.
At the moment the projectile and powder gases exit the muzzle of the barrel bore, the processes of internal ballistics end and the processes of external ballistics begin.
Processes external ballistics are traditionally considered from the point of view of the action of the main and additional factors of the shot. Under main factor a shot means the damaging effect of a projectile on an obstacle, i.e. the formation of any damage. By degree of change of a trace-perceiving object, all gunshot injuries can be divided into penetrating (with the penetration of the projectile not less than the length or diameter of the projectile) and superficial.
Penetrating injuries are divided into penetrating and blind, superficial- on tangents, ricochet marks and dents formed from a blow with an exhausted projectile.
Traces of additional shot factors must be considered in the system:
Phenomenon - Additional Shot Factors - Traces
First Appearance is the recoil of the weapon and its reflex return forward. As a result, when fired at close range or close to stop, the muzzle of the barrel (the front end of the bolt housing or barrel housing) hits the barrier, which is an additional factor in the shot. From this blow, a trace is formed on the barrier, called punch line .
Second phenomenon- expiration at high speed from the bore of powder gases. It creates a number of additional factors that are displayed through the following traces.
Mechanical impact powder gases on the barrier is displayed in the form of tears in the edges of damage resulting from the spreading of gases over the surface of the barrier. In this case, textile fabrics, felt and even dressed leather are damaged.
The next additional factor is thermal effect on the barrier. Its traces have significant variations: from slight singing of the pile of textile fabric to its charring.
An additional factor such as deposition on the barrier of substances that are part of the powder gases, is realized through three types of traces: a zone of soot deposition (coal lumps and metal particles), a zone of deposition or introduction of incompletely burned powders and a zone formed by grease spots.
Among the phenomena that give rise to additional factors of the shot include projectile surface contact with damage edges. The surface of the projectile affects the edges of the damage. This is evidenced primarily by such a trace as a wiping belt (metallization belt).
As a result of such an impact on synthetic materials (fabrics), traces of thermal nature are formed - sintering of the edges of the damage.
On the display of additional factors of the shot, i.e. The nature of the shot marks is also influenced by the physical (mainly mechanical) properties of the barrier material. Let's consider the most common of them.
Gunshot damage tree objects(boards) are largely determined by the degree of dryness (moisture) of the wood, as well as the angle at which the projectile enters the object. In a dry board with a perpendicular entry of the projectile, the inlet has a rounded shape and a diameter slightly exceeding the diameter of the leading part of the bullet. The edges of the inlet are uneven, serrated, the uneven edges are correlated with structural units - annual rings and layers of wood. The outlet usually has an irregular quadrangular shape. Its lateral sides, passing through the annual layers of wood, are quite even. The same sides that are located across these layers are uneven, jagged, with flakes and spalls.
Gunshot damage sheet metal(drainpipes, roofs, car bodies) have the shape of a funnel, tapering along the course of the projectile. The edges of the hole are shaped like the rays of an irregular star. The dimensions of the hole correspond quite accurately to the diameter of the bullet.
Gunshot damage sheet glass are characterized by a funnel-shaped or crater-shaped shape with expansion along the projectile. Radial and concentric cracks form around the damage. On the side faces of the cracks surrounding the damage, smaller cracks are formed, some ends of which are collected in a bundle, while others diverge like a panicle. At a meeting angle close to a direct one, the diameter of the damage on sheet glass corresponds quite accurately to the diameter of the bullet.
AT textile fabrics the projectile forms lesions of a rounded or quadrangular shape, depending on the structure of the tissue. The projectile destroys and carries away the fibers of the threads, and at the point of its contact with the barrier, the so-called “fabric minus” is formed, i.e. the clearance that remains when the ends of the threads come together along the edges of the damage. The ends of the threads are uneven, torn, facing into the lumen of the damage and inward, in the direction of the projectile. The dimensions of the inlet are usually somewhat smaller than the diameter of the bullet.
The same questions are put to the resolution of a forensic ballistic examination, although in order to solve them, in addition to the damage itself, it is necessary to present the weapon from which the shot was fired and similar experimental cartridges, especially to establish the distance of the shot.
