Q5 LONG ANSWER 10M ★ High-yield

Describe the injuries and death caused by electricity. Add a note on lightning.

Forensic Medicine · 2nd Professional — Para-Clinical

Factors Determining the Effect of Electricity

Factor	Effect
Current (amperage) — the factor that kills	Voltage is what is quoted, but amperage is what kills. About 1 mA is perceptible; 10 to 20 mA causes tetanic muscle contraction and the person cannot let GO; 50 to 100 mA causes ventricular fibrillation and is the lethal range; and above about 1 to 2 A the heart is thrown into arrest and may actually restart, so very high currents are sometimes survived
Voltage	Determines how much current flows for a given resistance. Low voltage (domestic, 220–240 V in India) typically kills by ventricular fibrillation; high voltage kills by respiratory arrest from paralysis of the respiratory centre and muscles, and by extensive burns
Resistance	The critical variable in practice. Dry, thick, callused skin has high resistance (up to a million ohms) and may be protective; wet or sweating skin has very low resistance (a few hundred ohms), so the same voltage passes a far larger current. This is why electrocution in a bathroom or with wet hands is so much more dangerous
Type of current	Alternating current is about three times more dangerous than direct current at the same voltage, because it causes tetanic muscle spasm preventing release, and because it more readily induces fibrillation at 50 to 60 Hz — precisely the domestic frequency
Duration of contact	Prolonged by the inability to let go; the longer the contact, the greater the damage
Pathway through the body	The most important single determinant of lethality. Hand TO hand or hand TO opposite foot passes through the heart and is the most dangerous; a path through the head involves the brain stem; and a path confined to one limb may cause only local damage

CLINICAL PEARL

It is the current that kills, and the resistance decides how much flows. The same 240-volt supply is survivable through dry, callused hands and lethal through wet ones, because wet skin drops the resistance from a million ohms to a few hundred and the current rises accordingly. This is the whole explanation for why bathroom and monsoon electrocutions are so common in India, and why the voltage alone tells you very little.

Findings in Electrocution

The JOULE burn (endogenous or electric mark) is the characteristic lesion at the entry point — a firm, painless, crater-shaped lesion with a raised, pale, blanched margin and a depressed grey-white centre, surrounded by a zone of hyperaemia. It is produced by heat generated within the tissue as the current meets resistance, and it characteristically reproduces the shape of the conductor
Histology is diagnostic — elongation and "streaming" of the epidermal nuclei in the direction of the current, with vacuolation of the epidermis and separation of the layers. This is the single most useful confirmatory test
Metallisation — metal from the conductor is vaporised and deposited in the skin, and can be identified chemically or by scanning electron microscopy, identifying the type of conductor
Exit wounds are usually on the feet, often larger and more ragged, and may be absent where the person was well earthed over a wide area
Other findings — the burns may be trivial or absent, particularly where the contact was wet or brief, and a completely negative external examination does not exclude electrocution; muscle tearing and fractures from violent tetanic contraction, including fracture-dislocation of the shoulder and compression fractures of the vertebrae; and internally, only congestion, so the diagnosis rests on the mark, the history and the scene

Lightning

Feature	Description
Nature	An enormous direct current at millions of volts, lasting only milliseconds; India records among the highest lightning death tolls in the world, mainly among farm workers
Filigree (arborescent, Lichtenberg) burns	The pathognomonic finding — superficial, reddish-brown, fern- or branching-tree-like markings on the skin, produced by the flash tracking over the moist surface. They fade within about 24 hours, so they must be photographed at once
Flashover	Much of the current passes over the wet surface of the body rather than through it, which is why a substantial proportion of victims survive
Effect on clothing and metal	Clothing may be torn off or shredded and shoes burst open by the sudden vaporisation of sweat and moisture; metal objects — coins, ornaments, keys — may be melted or magnetised, and may produce contact burns
Injuries	Burns, rupture of the tympanic membrane, ocular injury including cataract developing later, and blunt injuries from being thrown or from a falling tree
Cause of death	Cardiac asystole (rather than fibrillation, since it is a direct current) and respiratory arrest from paralysis of the respiratory centre. Because asystole may be followed by spontaneous return of the heartbeat while respiration remains paralysed, prolonged artificial ventilation saves lives — and this is the one situation in mass casualty where the apparently dead are treated first

Distinguishing Electrocution from Lightning

Feature	Electrocution (domestic or industrial)	Lightning
Current	Alternating, low voltage, prolonged contact	Direct, millions of volts, lasting milliseconds
Skin lesion	JOULE burn — a crater with a raised pale margin at the entry point, reproducing the conductor	Filigree (arborescent, Lichtenberg) burns — branching fern-like markings that fade within 24 hours
Cardiac effect	Ventricular fibrillation at low voltage	Asystole, which may be followed by spontaneous return of the heartbeat while respiration remains paralysed
Clothing and metal	Usually intact	Clothing torn off or shredded, shoes burst; metal melted or magnetised
Survival	Depends on the current and pathway	A substantial proportion survive, because of flashover over the wet skin
Resuscitation	Prolonged attempts justified	Prolonged ventilation is what saves; and triage is reversed — attend the apparently dead first
Histology of the mark	Nuclear streaming of the epidermis — diagnostic	Filigree burns show little histologically

Manner and Applied Aspects

Accidental electrocution is much the commonest — domestic appliances with faulty earthing, wet hands, bare wires, illegal power connections, contact with overhead lines by workers and by children flying kites with metallic string, and electric fences
Suicidal and homicidal electrocution are rare and require investigation of the scene and the wiring; judicial electrocution is not practised in India
Examine the scene and the appliance, and involve an electrical inspector; the diagnosis of electrocution often depends more on the circumstances and the demonstration of a fault than on the autopsy findings
Take skin from the suspected entry and exit marks for histology; nuclear streaming confirms the diagnosis when the mark itself is equivocal, and a burn of any other cause will not show it
Photograph filigree burns immediately; they fade within a day and are the pathognomonic sign of lightning, so a delayed examination loses the diagnosis permanently
Continue resuscitation far longer than usual in electrocution and lightning; the heart may restart spontaneously while respiration remains paralysed, and recovery after prolonged apparent death is well documented
Reverse the usual triage in a lightning mass casualty — attend to the apparently dead first, since those still breathing will generally survive and those in arrest may be saved by immediate ventilation
A negative autopsy does not exclude electrocution; where the contact was wet or over a broad area there may be no mark at all, and the diagnosis then rests entirely on the circumstances
The pathway decides lethality — hand to hand or hand to opposite foot passes through the heart, while a path confined to one limb may cause only local damage
Alternating current is about three times more dangerous than direct at the same voltage, because it locks the muscles and induces fibrillation at domestic frequencies
Metallisation identifies the conductor; vaporised metal deposited in the skin can be detected chemically or by scanning electron microscopy
Look for fractures from tetanic contraction — posterior shoulder dislocation and vertebral compression fractures occur without any external violence
Photograph filigree burns at once; they are pathognomonic of lightning and are gone within a day
Reverse triage in a lightning mass casualty — the breathing will usually survive, and the apparently dead may be saved by immediate ventilation
Wet skin drops the resistance a thousandfold, which is why the same supply is harmless dry and lethal wet, and why bathroom electrocution is so common
Involve an electrical inspector and examine the appliance; the diagnosis often rests on demonstrating the fault rather than on the body
Take skin for histology from every suspected electrical mark; nuclear streaming confirms it and no other burn produces it
High voltage kills by respiratory arrest, low voltage by fibrillation, which is why very high currents are occasionally survived
Amperage kills, not voltage; the fifty to hundred milliamp range causes ventricular fibrillation, and above one amp the heart may arrest and restart
Lightning gives asystole, not fibrillation, because it is a direct current — which is why prolonged ventilation rather than defibrillation is what saves
Domestic frequency is the worst case; fifty to sixty hertz alternating current is precisely the range most likely to induce fibrillation
An exit wound may be absent where the person was earthed over a wide area, so the absence of a second mark excludes nothing
Suicidal and homicidal electrocution are rare and need scene investigation; the wiring, the appliance and the position of the body carry most of the evidence

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