The field of ballistics deals with the study of arms and ammunition, as well as so-called terminal ballistics, the biologic impact of the projectiles.
Types of weapons used in gunshot wounds
Generally, a rough distinction is made between long-barreled weapons, also known as shotguns, and short-barreled weapons, meaning handguns.
The following firearms are long-barreled weapons:
- Rifles are guns with a long barrel with spirally arranged grooves (furrows) and ridges (spiral elevations). Rifles shoot bullets.
- Shotguns generally have a smooth barrel and shoot shotgun shells.
The following firearms are short-barreled weapons:
- Revolvers have a drum-shaped cylinder that revolves around each shot. The number of bullets contained in the cylinder differs according to the manufacturer and type. On the side of the gun, between the cylinder and the barrel, there is a space from which the gunshot residue escapes.
- Handguns feature a closed system; the cartridge chamber is located in the front part of the barrel. They can be classified into the so-called single-shot pistols, which have to be reloaded after each shot, and the multi-shot pistols, with repetitive action that is either manually or automatically controlled.
Furthermore, there are flare guns in the sports sector as well as air guns that use pneumatic pressure. The captive bolt guns or cattle stunners, respectively, and powder-activated guns such as nail guns used in construction are not weapons in the legal sense, but their functional principles are comparable and they are potentially life threatening.
Ammunition in gunshot wounds
Ammunition is the projectile that consists of three components: the projectile (the bullet or cartridge), the casing including the primer, and the charge in the form of the priming charge and propellant, which provides the pressure to allow motion of the projectile.
Forensically, the most important types of cartridges are bullets and shotgun shells. Bullets are usually made from lead and possibly have a full or partial metal jacket. Shotgun shells consist of coarse to very fine lead pellets. Between the shells and the propellant is wadding made of felt or plastic; at the top of the case, above the shot load, is a cap.
The charge of the projectile consists of a primer and propellant. The primer contains impact-variable substances with heavy metals such as barium, lead, or antimony; these are the basis for analysis of chemical gunshot residue. The propellant, on the other hand, usually consists of nitroglycerin in the form of powder flakes. After ignition, the nitroglycerin burns explosively and forms gas under extremely high pressure, propelling the bullet through the barrel.
Internal ballistics in gunshot wounds
Internal ballistics deals with all the processes within the gun. Once the trigger of a gun is pulled, the firing pin strikes the bottom of the cartridge, meaning the so-called primer. As a result, the impact-sensitive primer compound explodes and in turn ignites the propellant. This burns very rapidly, creating a lot of gas under enormous pressure and thus expelling the projectile at a very high speed through the barrel.
On exiting the barrel, the residue of both the primer and the propellant, the so-called gunshot residue, is released and can settle on the hand that fired the gun and on other objects. The gases can land explosively on the muzzle, causing the loud bang and recoil of the weapon.
Terminal ballistics on gunshot wounds
Terminal ballistics deals with the biologic effects of the projectile in human beings. These include the effect from the entrance, the penetration, and the exit from the tissue as well as the effects of powder combustion gases and load residues.
Typical findings of entrance wounds are a central substance defect, an abrasion collar, a contact ring (also called a ‘gunshot residue ring’), and a contusion collar with blood exiting. The contact ring is regarded as a reliable criterion for a projectile impact. The other features are merely signs of blunt force. An equally important differentiating feature is that the entrance wound defect is not adaptable.
A through-and-through shot produces hole fractures (especially in the skull) and comminuted fractures (especially in the long bones). Hole fractures are usually cone shaped, which can lead to an understanding of the direction of the shot. Also, the bone fragments in comminuted fractures are displaced in the direction of the movement of the projectile.
In soft tissues, hydrostatic shock takes place. The high bullet velocity creates a temporary wound cavity and a cave-like rupture of tissues that contain water, such as the muscles or the brain. A shock wave originating from the temporary wound cavity leads to organ damage in the surrounding area.
An exit wound is characterized by a laceration-like defect, which tends to be smaller than the projectile caliber, as the projectile stretches the skin from the inside. Also, there is no central substance defect, no laceration, and no abrasion. Bone fragments can act as secondary projectiles and sometimes cause a large exit wound. The same applies to projectiles with partial jackets that split during penetration.
Special gunshot wounds are the result of the ricochet and the Kroenlein shot. An injury caused by a ricochet is due to a projectile that was diverted outside the body. The Kroenlein shot is defined as a bursting of the cranial cavity due to the increase in intracranial pressure.
Gunshot residue in gunshot wounds
The explosion gases that exit the muzzle immediately after the projectile are composed of unburnt or partially burnt powder flakes; gunshot residue; carbon monoxide; carbon dioxide; elements of ignition such as lead, antimony, and barium; and, possibly, components of weapon care products.
An abrasion collar occurs when the gun barrel is close to the target area. Here, the load residues deposit themselves around the entrance wound like a halo. The firing distance can be determined based on the appearance of the residue image: The greater the distance, the fewer heavy particles reach the skin.
Shooting distance in gunshot wounds
Gunshots are divided into long-range and close-range shots. Furthermore, close-range shots are divided into relative and absolute.
With long-range shots, no residue is found around the entrance wound. With relative close-range shots the residue is found on the skin, and with absolute close-range shots, the residue is even found under the skin.
During an absolute close-range shot, the barrel is placed directly on the skin, causing the explosion of gases to penetrate the skin, spread radially, and rupture the subcutaneous fat tissue. The result is the so-called abrasion collar with powder stippling and carbon monoxide.
With this shot, the blood that pours out appears bright red and contains CO hemoglobin (carboxyhemoglobin). Simultaneously, the skin distends with a radial rupture in the form of a laceration. As the skin touches the hot barrel, a punch mark in the shape of the muzzle forms.
The punch mark provides important information for crime reconstruction, providing clues about the shape, the type of weapon, the shooting position during the shot, and the handedness (in suicide).
Firearm injuries are classified depending on the velocity of the projectile. Velocities < 600 m/s produce low-velocity wounds and are more commonly seen in civilians. Velocities > 600 m/s produce more severe injury and are commonly seen with military or hunting weapons with a muzzle.
Special case: captive bolt gun
The result of gunshot wounds from a captive bolt gun is a bone punch, without finding any projectile in the barrel.
Shooting hand in gunshot wounds
The determination of the shooting hand provides important clues about the perpetrator. Gunshot residue is found on the thumb and forefinger—especially when using revolvers. Furthermore, blood splatters that are thrown back from the entrance wound can end up on the outer surface of the fingers.
Back splatter can be found on hands and clothes in the form of small bone fragments and tissue shreds. Furthermore, the use of assault rifles frequently results in skin lacerations on the inside of the hands because of the lateral escape of explosive gases.
Differentiation among crimes, accidents, and suicides in gunshot wounds
|Range of fire||Usually a long-range shot, rarely a close-range shot; surprised while sleeping, etc.||Often a relatively short-range shot that occurs while manipulating a weapon, such as when cleaning or disassembling it||Usually an absolute close-range shot|
|Terminal ballistics||Entrance wound possible on every part of the body; clothing is shot through||Entrance wound in chest, face, or open eye||Frequently in the forehead, temple, mouth; very rarely in the back of the head; clothing is pushed aside|
|Type of weapon||No weapon present, often only the ejected shell casings||The total scene needs to be observed||Own weapon and ammunition; weapon in the hand or on the floor|
|Residue||Bullet impact in the wall or floor after a through-and-through shot, mostly not in the ceiling||Projectile impact in wall and ceiling||Projectile impact often in ceiling|
Gunshot injuries to the cranium/brain are often lethal, especially after suicide attempts. For patients with gunshot injuries to the torso, hemodynamic stability is a deciding factor in prognosis/management.
Burns and Scalds
Burns are injuries caused by direct exposure to flames, radiant heat, or hot gases such as steam or combustion gases. Scalds occur from hot liquids such as water or oil; runoff traces on the skin are typical for scalds.
Findings on the corpse or survivor in burns and scalds
- Skin: First-degree burns results in redness and heal well in a short period of time. Second-degree burns result in blister formation; complete healing is possible. Third-degree burns produce superficial necrosis, with the defect healing in the form of a scar. Fourth-degree burns result in deep necrosis with charring.
- Hair: Hair can burn but cannot scale. When burned, hair will turn crinkly to the point of breaking down.
- Soft tissues: The musculature boils and shrinks, resulting in bending of the joints. The corpse takes on the so-called boxer or fencing position.
- Teeth: These are very resistant to heat; they can serve in the identification of the body even with strong charring.
- Head: Heat hematomas, the result of postmortem bleeding in the skull, are frequent. The bleeding is caused by a contraction of the dura mater with a detachment from the calvaria during which the veins rupture. Furthermore, the heat can blow up the skull.
Signs of vital reactions in burns and scalds
Among the signs of vital reactions is redness of the skin and skin blisters. All the other external findings may also occur on the corpse, for which only an internal autopsy can provide further information.
When respiratory function is maintained, combustion gases such as carbon monoxide (CO), carbon dioxide (CO2), and hydrogen cyanide reach the respiratory organs and are traceable in the blood of the corpse. Also traceable is the smut on the mouth and the nostrils, sooty material in the trachea, heat changes in the mucous membrane, acid burns from the combustion gases in the respiratory tracts, and with CO poisoning, a bright cherry red color of the livor mortis and internal organs.
Also, crow’s feet can form because of a victim squeezing their eyes shut. Because squeezing the eyes shut leads to some areas around the eyes being spared from soot, wrinkles result.
In the following cases vital reactions do not occur:
- Cyanide poisoning
- Flash fire: The result of the heat is a laryngospasm and respiratory arrest.
- Heat rigor: A functioning impairment of respiratory excursion is caused by the sudden onset of heat rigor on the chest cavity, resulting in death.
Causes of death in burns and scalds
In general, CO poisoning and lack of oxygen (O2) (O2 loss as a result of the fire) quickly lead to death by suffocation. Delayed death in cases of very strong burns may occur because of a water–electrolyte imbalance, infections, burns to the airways, and pulmonary edema. This is what a lung with acute inhalation injury looks like:
The rule of nines in burns and scalds
The fatal outcome as a result of burns depends on the percentage of the total body-surface area that has been burned and the biologic age of the victim. As a rule, a burn of over 70% of the body surface is fatal.
The rule of thumb is that if the sum of the victim’s age and the percentage of the body surface burned is significantly below 100, there is doubt as to whether death occurred as a result of the burns. In this case, an autopsy and a toxicologic examination are necessary.
The rule of nines is a helpful method for estimating how much body surface area has been burned. It states that the head, the chest, the abdomen and the back (the top or bottom, respectively), the front or back of the arms, and the thighs and the lower legs (front and back, respectively) each corresponds to 9% of the body surface. A burn of the size of the palm of a hand corresponds to 1%.
Differentiating among burn occurrences in crimes, accidents, suicides, and postmortem incidents
|Characteristics||Victims usually unconscious because of stabbing, beating, or strangulation||Often surprised in the home by a smoldering fire while sleeping or caused by children/elderly people||Mostly outdoors after dousing with an accelerant||Occurs by setting fire to an object containing the body to cover up a crime (so-called arson murder)|
Injuries and deaths by electrical impact can result if a person becomes a part of an electrical circuit caused by a short circuit or an accidental ground circuit.
Current flow is significant in the biologic effect. This flow is essentially determined by skin resistance, which is in the range of 100 Ω (moist skin) to 100,000 Ω (dry skin). Equally important is the path that the current takes as it travels through the body.
Thermal effects through Joule heat in electricity
Heat damage due to high local current density at electrical crossings appears in the form of redness, blisters, and funnel-shaped burns—collectively referred to as the electric mark (Joule burn). This is a purely thermal effect and not a sign of a vital reaction.
The Joule burn is usually round, dented, and gray-white to black in color. An undulating edge (porcelain wall) is just as typical as a histologically detectable parallel arrangement of basal cells. With a large contact area such as water, the current density at the crossing point is low, and there is no electric mark.
Direct contact with the current conductor creates a small electric arc whereby the metal component of the current conductor vaporizes and is deposited on the electric mark. This metallization leaves no vital signs. During a current flashover, burn marks appear on the soles of the shoes or the sleeves of jackets.
Specific effects due to depolarization in electricity
Because current can depolarize tissue, heart arrhythmias can be caused, leading to instant death and overstretching and tears of the musculature.
Myoglobin exiting from the muscles can pass via the blood into the kidneys and lead to crushing syndrome in the kidneys with possible renal failure. The contraction of the respiratory musculature can lead to congested bleedings and breathing difficulties.
Other autopsy findings are pulmonary edema, liquid cadaveric blood, and an abundance of the blood of the internal organs, as well as soft-tissue edema.
Dangerous areas with electricity
Even low currents of a few milliamperes (mA) have biologic effects. Effects can occur with the following currents:
- Current above 5 mA: muscle traction
- Current above 25 mA: releasing is impossible
- Current above 80 mA: cardiac arrhythmias
- Current above 800 mA: guaranteed fatality
- Current from 2A: electric marks and severe burns
Differentiating among crimes, accidents, suicides, and postmortem incidents with electricity
|Characteristics||Hair dryer or power cord was placed into a bathtub; the current is applied to a doorknob||Amateur electrician; contact with defective household appliances||Mostly death in bathtub||Simulated electrocution; electric marks may be present|
Special event: electrocution in the bathtub
The condition for damage is a closed circuit. As a rule, the ground fault occurs via a metal shower hose or a metal drainpipe. Because of the low skin resistance, usually no electric marks are found. The fuses will not blow.
It is difficult to provide evidence of killing if the electrical sources have subsequently been eliminated. The absence of typical drowning signs would be suspicious, especially if narcotics are found in the victim’s blood. In such cases, an autopsy, as well as criminal and electrotechnic clarification, must take place.
Special event: death in a high-voltage area
In a high-voltage area, i.e. railroad tracks or power lines, a direct conductor contact is not necessary because the current can skip about 1 cm/1,000 V. Hereby, a bright and very hot light arc is created.
Superficial burns, singed clothing, and melted belt buckles or buttons can be found. The bright light leads to the victims squeezing their eyes shut, thus producing so-called crow’s feet, with areas with no burns at the outer corners of the eyes.
These kinds of deaths usually happen because of accidents, but the death can also be a crime if someone was pushed into the danger zone.
Special event: death by lightning
In death by lightning, one distinguishes between a direct and indirect lightning effect. The direct lightning effect corresponds with the effects of a high-voltage accident. The indirect lightning effect is produced far from the lightning strike impact. The cause of this is an exponential drop of the voltage around the lightning impact site, the so-called discharge voltage pattern.
If the individual in this area is standing on the ground with spread legs, the feet may be in areas of different voltage (step voltage) and because of this voltage difference, current flows through the body.
Fine, branched reddening, similar to the lightning phenomena in the sky, may appear on the legs of victims; this is referred to as the Lichtenberg figure.
Death by Freezing and Hypothermia
Even small changes in body temperature can be dangerous. Heat loss can occur because of radiation (emission), conduction (direct heat transfer to the environment), evaporation (withdrawal of evaporation heat), and convection (ventilation).
Low insulation promotes heat loss with a thin layer of fat or inadequate clothing, a low volume of body-surface area (as in infants), and an increased heat transfer through a moist environment or heat-conducting materials such as wet soil or cold water.
Also, alcohol promotes heat loss due to the increased blood flow in the skin. Hypothermia is when the core body temperature is below 35°C.
If the thermoregulation of the body has been exhausted because of muscle tremors and centralization of the circulation, the body core cools down. Cooled hemoglobin has a higher affinity to oxygen (O2), which results in tissue hypoxia. Thus, death occurs through inner suffocation and consequent cardiac arrhythmias, such as ventricular fibrillation.
Local frostbite is divided into three stages:
- First, erythema (dermatitis congelationis erythematosa) and numbness occur.
- Swelling (dermatitis congelationis bullosa) and blistering (chilblain) follow.
- Finally, necrosis (dermatitis congelationis gangrenosa) with blackening occurs.
Findings on the corpse in deaths by freezing and hypothermia
- The brain: Disturbances of consciousness and hallucinations occur.
- The heart: At temperatures of 30°C and below, body temperature arrhythmias occur, and at temperatures of 27°C and below, death by ventricular fibrillation occurs.
- The skin: Perniones are hemolysis spots (also referred to as ‘cold spots’) on the extension side of the extremities (usually on the forearms and lower legs); they are reddish and look like traumatic bleeding. They can be distinguished from the latter by the fact that the subcutaneous fat is not pinched. Furthermore, red, itchy, or painful swelling appears underneath the skin (frostbite). These occur particularly in parts of the body with less blood supply, such as toes, fingers, and ears.
- The stomach: Wischnewsky spots are hemorrhagic erosions of the gastric mucosa that are typical in death caused by freezing.
- The musculature: Small bleedings are located particularly in the musculature of the body core and microscopic tears of the muscle fiber, i.e. in the ileopsoas muscle.
- Changes in the blood: High blood sugar, acidosis, and ketoacidosis occur as a result of fat breakdown. The blood has a bright red color due to the stronger binding of O2 to hemoglobin.
Paradox sensation of warmth in deaths by freezing or hypothermia
It is quite typical to find a partially or completely undressed frozen corpse so that initially suspicion of a sexual offense may occur. People with hypothermia undress because the increased blood circulation in the skin during the dying stage leads to an intense feeling of warmth.
Because these victims also experience hallucinations because of the lack of oxygen, they ignore the reality and dispose of some or all of their clothing. Alcohol intoxication promotes this thought process.
Differentiating among crimes, accidents, and suicides with deaths by freezing or hypothermia
|People affected||Exposed newborns or abandoned alcoholics||Alcoholics, drug addicts, and homeless people who sleep outdoors||As part of a mental disorder|
|Characteristics||Cold water is especially dangerous; the rule of thumb for survival: 1 min/1°C|
In cases of death in water, one has to differentiate between an indirect and a direct drowning. The indirect or atypical drowning is submersion in water due to circulatory collapse or disturbance of consciousness. This includes the classic death by drowning according to Emminger (sudden death in the water).
Direct drowning, on the other hand, is suffocation underwater comprising the following criteria: gasping for air before going under, holding one’s breath after going under (possibly several repetitions of these two processes), shortness of breath with breathing out and inhaling water, and a preterminal pause for breath due to paralysis and death. Overall, drowning takes between 3 and 5 minutes.
Special event: death in the bathroom
Death in the bathroom refers to death while coincidentally being in water. Often, this occurs in the bathtub because of an abrupt collapse of the main vital functions, so that all vital reactions are lost.
Vital reactions during drowning
Coughing and the convulsions during drowning result in the so-called plume of froth at the mouth and nose in recent drowning victims, which can also be seen after it has dried. This whitish foam is produced by the reflective inhalation of water, which mixes with breathing air and the protein-rich bronchial secretions.
Also, a spasmodic inspiration leads to an inflation of the lungs causing bleeding again, the so-called Paltauf spots. These spots are about the size of a fingertip, are subpleural, and are red to brown in color. The macroscopic image of the bloated, red lung is called emphysema aquosum (only when drowning in fresh water). The lung cannot even be collapsed with the pressure of a finger (volumen pulmonum auctum).
Water is found in the alveoli, typically with elements such as plankton and diatoms. With a sediment analysis of the discovery site and an analysis of the composition of the water in the lungs, the drowning site may be reconstructed.
As the water was ingested, it can also be found in the stomach. The stomach contents are therefore typically three-layered: foam is at the top followed by water and finally chyme; this formation is referred to as Wydler’s sign.
The reflexive vomiting of water also leads to tears of the mucosa of the cardia, the Sehrt’s mucosal tear. Another common finding is Svechniko’s sign; it describes the presence of the drowning fluid in the sphenoid sinus.
All these findings prove that the person was alive when getting into the water.
Drowned body and drowning
The sign of a longer stay in water is wet clothing and clothing contaminated with mud, injuries caused by floating, injuries caused by boat propellers, wrinkled hands with nail detachment, adipocere (wax-like formation on the skin), and bloating of the corpse that was fed on by animals.
As the body floats in a facedown position, abrasions occur mostly on the forehead, the back of the hands, the knees, and the toes.