The injuries caused by contact with electrical conductors depends upon: (1) The kind of current: Alternating current is 4 to 5 times as dangerous as an equal voltage of direct current. (2) The amount of current: The amount of current that will flow through or over the body may be determined by the formula CV/R. where C is the current in volts and R is the resistance of the body in ohms. The flow of the current through the body is great, if the voltage is high or if the resistance is low. Electrocution is rare at less than 100 volts, and most deaths occur at more than 200 volts. Currents of 10mA cause pain and muscle contractions, over 60mA are dangerous, and 100 mA is fatal. High voltages may cause the victim to be thrown clear, while lower tensions, around 240, cause muscle contraction, due to which the victim holds on to the source of the current. (3) The path of the current: Death is more likely to occur if the brain stem or heart are in the direct path of the current. (4) Duration of the current flow: The severity is directly proportional to the duration of current flow. For an electric shock to occur there must be contact by the body with both a positive and negative pole, or alternatively, the ‘earth’. The earth may be any object not insulated from the ground. When earthing of the body is poor, as with dry and rubber shoes, carpets, wooden floors and upstairs premises, fatal electrocution is uncommon. The effects of electricity depends on the voltage and the resistance offered by the body. Of the body is well insulated, if does not conduct the current and no harm results. Dry skin offers high resistance but the resistance is diminished when the skin is moist or covered with sweat. Blood has a low resistance, and as such within the body, electricity tends to be conducted along blood vessels. Predisposing factors are unexpectedness of shock, anxiety, fear and emotions, exhaustion, cardiovascular and other diseases.
The current passes through the skin producing heat, which causes boiling and electrolysis of tissue fluids. The skin explodes and rolls back from the surface. A well-moistened skin may not show electrical burn, while a thick dry skin may show well-marked electrical burn.
The electric mark (Joule burn): It is specific and diagnostic of contact with electricity and is found at the point of entry of the current. These marks are round or oval, shallow craters, one to 3 cm. in diameter, and have a ridge of skin of about one to 3mm. high, around part or the whole of their circumference. The crater floor is lined by pale flattened skin. In some marks, the skin may break within or near the margin of the crater, resembling that of a broken blister. The skin of the mark is pale, but there may be mild hyperaemia of the adjacent intact skin, due to rapid dilation of pre-capillary vessels. When contact is more prolonged, the skin in the mark becomes brown and with further contact, there may be charring. Occasionally, the mark may have a distinctive pattern, that of the shape of the conductor. Rarely, the mark may be present as a circular hole, penetrating skin, muscle, and even bone, so as to simulate a bullet wound. These electric marks are produced by the conversion of electricity into heat within the tissues. They are commonly found on exposed parts of the body, especially on the palmar aspect of the hands.
Microblisters develop within the squamous epithelium and in the external horny layer, due to the cooking effect on the tissues. They represent defects through which the steam exited. Larger vacuoles are produced within the epidermal cells, the nuclei. These flattened cells usually stain darker than the normal cells with haemotoxylin and eosin. The nuclei of the vascular media tend to be twisted to resemble spirals, which may be seen at distant points from the site of contact with the electrode. These may be localized degeneration of the intima. Tearing of elastic fibres and the overlying intima is common and may cause secondary thrombosis.
Exit Marks: These are variable in appearance, but they have some of the features of entrance marks. There may be more damage of tissues, and they are often seen as splits in the skin at points where the skin has been raised into ridges by the passage of current; splitting of these ridges may be continuous or interrupted.
External: The examination of the scene may be much more important than the post-mortem of the body. The face is pale, the eyes are congested and the pupils dilated. Rigor mortis appears early, and post-mortem lividity is well developed. Usually there are external marks of electric burning, and contusion or laceration at the point of entrance and exit of the body. In some cases, the lesions may extend through subcutaneous tissues and involve muscles and bone. A number of grayish-white circular spots, which are firm to the touch and free from zone of inflammation may be found at the site of entrance and exit. Severe convulsions caused by electrical discharge may cause fractures of the spine or limbs. Extensive ecchymosed may be found on the skin of the trunk. In some cases, external lesions may be absent and frequently they are so slight as to require careful search. The clothing, including shoes, gloves and headgear should be examined for burns. Occasionally, only the hair is singed. Arcing of the current may produce characteristic pit-like defects on the surface of the hair. Any metallic objects on the body will produce corresponding burns on the skin because it becomes heated by the passage of the current. The color varies depending on the composition of the conductor, i.e., brown or black if of iron, or yellow-brown if of copper. This metallization is due to the volatilization of the metal, particles of which are driven into the skin. Metallization produced by low or medium voltage may be detected under low magnification or by histological or chemical examination. Current marks may be hidden inside the oral cavity, from putting live wires into the mouth or from drinking at a water fountain in contact with electric current. They may be found in the urethra due to urination on a high tension wire. In some cases, the entrance and exit marks cannot be determined grossly. Occasionally, the site of entrance may be determined by histochemical methods or by electron microscopy from the deposition of metal particles on the skin.
Internal: The appearances are usually those of asphyxia. The lungs are congested and edematous, and the brain, meninges and parenchymatous organs are congested. Petechial hemorrhages may be found along the line of the passage of the current, under the endocardium, pericardium, pleura, brain and the spinal cord. There may be necrosis of the intima, or of the complete wall of the blood vessels. Vascular thromboses may be seen in the vicinity of electrical burns. Skeletal muscle in the path of the current may show Zenker’s degeneration, often with spiraling and fragmentation of fibres. High amperage has an explosive effect and may produce injuries resembling bullet, stab or cut wounds. Small balls of molten metal, derived from the metal of the contacting electrode, so-called current pearls, may be carried deep into the tissues. Heat generated by the current may melt the calcium phosphate, which is seen radiologically as typical round density foci (‘bone pearls’ pr ‘wax drippings’). There may be bone necrosis, and zigzag micro fractures. Focal petechial haemorrhages are found in the brain and spinal cord, especially in the medulla and the grey of the pyramidal nuclei and of the anterior horns and the Purkinje cells of the cerebellum; wide dilatations of the perivascular spaces especially in the brain stem and cervical cord; fragmentation of the axons, and changes in the myelin sheaths of peripheral nerves are noted. In some cases, irregular tears and fissures in the brain tissue and rupture of walls of arteries are seen. A foetus may survive the electrocuted mother or a surviving mother may abort after electric injury. Occasionally, no lesions can be found either externally or internally. Death in these cases may be due to vagal stimulation.
Cause of Death:
Circuits from any of the limbs to the head involve the brain stem and upper cervical cord. Arm-to-arm circuit may also involve the upper cervical cord. In these cases, death probably occurs from paralysis of medullary (respiratory) centers. Arm-to-arm or left arm to either leg circuits involve the heart and death occurs either from ventricular fibrillation or cardiac arrest without fibrillation. Death need not be instantaneous. Individuals may be able to walk some distance and talk before the onset of collapse and death.
Death by electric currents are usually accidental from defective electric appliances or negligence in the use of equipment. In industry, deaths may result from contact with live overhead cables or from handling of charged lamps, tools or switchgears. Rarely, death may occur during convulsive therapy to mental patients but cases of suicide, and even homicide have occurred. The viscera should be analyzed to know whether the victim was impaired at the time of the accident. Suicide is rare. A person usually winds wires round his fingers or wrists, which are then connected to the mains supply by means of a plug and the current is switched on.
Judicial Electrocution: Death penalty is carried out in the electric chair in some states is the
A flash or bolt of lightning is due to an electrical discharge from a cloud to the earth. The electric current is direct with a potential of 1,000 million volts or more. Along the track f the current much energy is liberated, most of which is converted into light. It is attracted b the highest points. It passes normally along the outside of a conductor, and as such, persons in buildings are relatively safe from electrocution. Dry skin and dry clothes are bad conductors, whereas wet skin and wet clothes are good conductors. Lightning or atmospheric electricity differs from ordinary electric current only in degree. A lightning bolt may injure or kill a person by a direct strike, a side-flash, or conduction through another object. In a direct strike or a side-flash strike, the current can spread over the surface of the body, enter it or follow both routes. In a side-flash strike, the flash of lightning hits an object, e.g. a tree, and jumping from it, strikes the person. In conduction through another object, the lightning hits a metallic object, flows through it, and strikes a grounded person touching it.
Symptoms: Unconsciousness is immediate. In non-fatal cases the person complains of giddiness, ringing in the ears and headache. In severe shock, the individual may suffer from hemorrhages or detachment, and later from loss of memory, anesthesia, paralysis, titanic convulsions, delirium, blindness, deafness or dumbness.
Post-mortem Appearances: Four factors are involved: (1) direct effect from electric discharge passing to earth, (2) surface ‘flash’ burns from the discharge, (3) mechanical effect due to force of displaced air around the flash by heat expansion, and (4) compression effect due to air movement in its return wave. The clothes are usually burnt or torn at the point of entrance and exit. In some cases, the clothes may be stripped off the body and thrown to some distance. In exceptional cases, clothing is not damaged even though the person is killed by lightning. Conversely, clothing may be burnt without any injury to the person. The expanded, displaced air causes disruptive or blast-like lesions, e.g., contusions, lacerations, fractures, ruptures of organs, wounds of almost any variety, burns, etc. Rigor mortis may appear soon and pass off quickly. Intense edema of the skin develops at points of entry of current in those who survive, probably due to paralysis of local capillary and lymphatic vessels.
The burns may be:
Cause of Death:
Involvement of the central nervous system with paralysis of the heart or of the respiratory centre causes death.
Less than half of the persons struck by lightning are killed. Death is always due to accident. Sometimes, the appearances left on the human body closely resemble those produced by criminal violence. Thus a person may be found dead in an open field or on the highway and body may show contusions, lacerations and fractures. In such cases, the diagnosis should be based on the history of a thunderstorm in the locality, evidence of effects of lightning in the vicinity of the body, and fusion or magnetization of metallic substances.
Most deaths from electrocution are accidental. In home, accidents results from contact with line electrical supply lines; the majority of the accidents being caused by defective equipment or negligence in the use of equipment. In industry, fatalities occasionally result from contact with line overhead cables or from handling of charged lamps, tools or switch gears.
Most cases pore nor investigative problems. Even if the death is not witnessed, examination of place for occurrence will reveal evidence indicating the possibility of electrocution. In white wasting or repairing walls the distance of wire is very important.
At the scene of death there may be evidence of disruption of the ground, building and other objects caused by lighting.
The clothing of the victim may show extensive tears with scorches or burns. The shoe and tight clothing may be burst open. The body may, likewise, show extensive tears and splits in the skin, opening of body cavities and fractures of the bones. The metallic objects on the body may show melting.