Electrocution: Low-Voltage, High-Voltage and Lightning

The four determinants of electrical injury are current magnitude (amperes), voltage, resistance at the contact point, and duration of exposure. Ohm's law connects the first three: current equals voltage divided by resistance. Dry skin has a resistance of 100,000 ohms or more; wet or abraded skin may fall to 1,000 ohms or less. A worker with sweaty hands contacting 230 V may draw 230 mA, a current well above the fibrillation threshold; the same worker with dry skin draws roughly 2.3 mA, producing only a transient sensation.

The physiological effects are current-dependent, not voltage-dependent. At 1-5 mA, a threshold tingling sensation. At 10-20 mA, sustained tetanic muscle contraction: the "can't let go" threshold at which the victim's flexor muscles override their ability to release a gripped conductor, a critical feature of domestic-appliance deaths where a victim grips a faulty device. At 50-80 mA, respiratory-muscle tetany producing asphyxia. At 100-300 mA through the thorax, ventricular fibrillation, which at domestic voltages is the primary mechanism of death. Above 1,000 mA, myocardial standstill (asystole), which can paradoxically be more survivable than fibrillation because it may revert to a perfusing rhythm on release of the current. Above several amperes, severe thermal injury to cardiac muscle and conduction tissue.

Cardiac rhythm at the moment of contact matters: current reaching the ventricles during the vulnerable T-wave period (the relative refractory period of cardiac repolarisation) triggers ventricular fibrillation at lower current thresholds than current reaching the ventricles in systole. This explains why a brief low-energy contact can be fatal when timing is unfavourable, while a prolonged moderate-energy contact may not be.

In India, the Central Electricity Authority's 2016 report on electrical accidents in India documented that 43% of fatalities involved domestic 230-V circuits, 32% involved low-tension distribution (415 V, three-phase), and the remainder involved high-tension transmission. Studies from the IIT Roorkee Department of Electrical Engineering and from AIIMS New Delhi (published in JIAFM vol. 34-38) corroborate the predominance of domestic voltage in residential fatalities, with agricultural pump-motor contacts as the primary occupational exposure in rural India.

Low-voltage electrocution (below 1,000 V, typically 110-240 V domestic supply) produces the most diagnostically subtle and most frequently encountered autopsy findings. The external marks may be absent, minimal, or confined to a small area easily overlooked without systematic examination of the hands, feet, and any surfaces that may have been in contact with a conductor.

The Joule burn at the entry point is the classic finding. It is pale, raised, slightly indurated, often with a central parchment-like zone of dessication and a narrow surrounding rim of erythema. The size is typically 0.5-2 cm, corresponding to the contact area of the conductor. In contrast to thermal burns, Joule burns show minimal soot deposition and no singeing of the surrounding hair (unless the contact sparked). Histologically, the entry burn shows coagulative necrosis of the epidermis and upper dermis with "streaming" of cell nuclei in the direction of current flow, a finding described by Jaffe (1928) and confirmed in subsequent histopathological series from the AIIMS forensic pathology department and from the Department of Legal Medicine, University of Frankfurt.

The exit burn, where current leaves the body to earth, is typically at the feet or another point of contact with an earthed surface. It may be less well-defined than the entry burn, particularly if the current dispersed through a broad contact area (e.g. wet flooring). When both entry and exit burns are identified and documented with photographs, the current path through the body can be reconstructed, which has direct implications for the cardiac-rhythm-disturbance mechanism: a current path from one hand to both feet passes through the chest and heart, while a path from one hand to the other hand also traverses the thorax and is equally lethal.

The arborescent (fern-like) burn pattern is a feature of flash-over effects at intermediate voltages (400-1,000 V) and at the current-dispersal areas in lightning injury (described in detail in the lightning section below). In domestic low-voltage electrocution it is rare; its presence in a 230-V domestic-contact case should prompt re-examination of the voltage source.

A crucial scene correlation: in a suspected domestic electrocution, the pathologist and the crime-scene officer must coordinate to identify the faulty device, the circuit breaker state, and any marks on the scene surface (melted insulation, carbonised contact points). In the 2003 Bihar election-period deaths, where electrocution was used in a public-order incident, the lack of scene examination meant that no circuit-level evidence survived, and the cause-of-death determination relied entirely on the autopsy burn findings and COHb measurement (which was absent, excluding concurrent fire; the COHb threshold for ante-mortem fire exposure is discussed in chemical asphyxia: CO, cyanide and hydrogen sulphide). In the US, NIOSH fatality investigation reports (available at cdc.gov/niosh/face) document electrical fatalities with detailed scene reconstructions that cross-calibrate with the autopsy findings.

High-voltage electrocution (above 1,000 V, typically 11 kV, 33 kV, 66 kV, or 220-400 kV transmission lines) produces a fundamentally different injury pattern from domestic voltage. The arc flash, a plasma discharge that forms when current bridges the air gap between a charged conductor and an earthed object, reaches temperatures of 10,000-20,000 K and radiates intense ultraviolet light. The flash itself causes flash burns to all exposed skin within the arc radius, ignites clothing and hair, and may produce blast barotrauma from rapid air expansion.

Contact or near-contact high-voltage injuries cause massive thermal destruction: third- and fourth-degree burns over large areas, deep tissue charring with involvement of underlying muscle and bone, and sometimes total carbonisation of the distal extremities that made contact. The skin at the contact point may show metallisation: the vaporised conductor metal is impregnated into the dermis and is recoverable by X-ray fluorescence (XRF) or scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS). Identifying the metal composition allows the forensic examiner to match the body to a specific conductor if scene examination is incomplete.

Visceral injuries in high-voltage deaths include cardiac muscle destruction, renal tubular necrosis from myoglobin released by extensive muscle breakdown (rhabdomyolysis), and, in survivors, cataract formation (the lens is particularly sensitive to the electromagnetic radiation component of high-voltage arc discharge). Internal organs along the current path may show focal coagulative necrosis without external findings at those sites, as deep tissue heating occurs without surface manifestation.

In the UK, the Health and Safety Executive (HSE) classifies electrical fatalities in its RIDDOR reports (Reporting of Injuries, Diseases and Dangerous Occurrences Regulations). High-voltage fatalities in the UK predominantly involve utility-line maintenance workers and construction workers using mobile plant equipment near overhead lines. Post-mortem investigations are coordinated with the HSE Electrical Equipment Safety team, and the forensic pathologist's findings on burn distribution and contact-point metallisation are integrated into the investigation of whether the site had been de-energised per safe-working-at-height regulations.

In India, the IIT Roorkee Department of High Voltage Engineering and the National Electrical Safety Code (NESC equivalent: Central Electricity Authority General Regulations 2010) document high-voltage fatality patterns in power-sector maintenance. The 2009 Maharashtra transmission-line fatalities (documented in the Maharashtra Electrical Inspectorate annual report) involved four workers on a 220-kV line whose bodies showed arc-flash injuries to the head and upper trunk consistent with flash-over prior to contact, with metallisation of copper conductors identified on forearm skin by AIIMS toxicology.

A lightning strike delivers a charge in the range of 1-20 coulombs at potential differences of 100-300 million volts over a discharge duration of 0.1-1 millisecond. The peak current may reach 20,000-200,000 amperes, but the ultra-brief duration means the total energy deposited is less than that of sustained high-voltage electrocution, which accounts for the higher survival rate among lightning-strike victims. The mechanical, thermal, and electromagnetic effects are qualitatively different from any other electrical exposure.

The Lichtenberg figure, first described by Georg Christoph Lichtenberg in 1777 as an electrostatic fractal discharge pattern on insulator surfaces, appears on human skin as a ferning, branching, erythematous pattern (arborescent or flashover burn) that tracks the superficial current path as the lightning discharge partially flashes over the body surface. It is pathognomonic of lightning strike, appearing within minutes to hours of the event and fading within 24-48 hours; documentation at the earliest opportunity is essential. The pattern was described in the medico-legal context by Cooper (1984) and has since become a standard documentation target in lightning fatality autopsy protocols in the US (National Weather Service Lightning Safety), the UK (Royal College of Physicians), and Germany (BKA forensic pathology department).

Lightning strike disrupts the magnetic domains of small ferromagnetic metals in contact with the body: belt buckles, watch straps, piercing jewellery, and coins may be magnetised by the electromagnetic pulse component of the strike. This finding, identified with a small compass at the scene, is not specific to any particular current path but confirms the presence of a large electromagnetic pulse consistent with lightning rather than other electrical discharges.

Eardrum perforation and eye injury (haemorrhage, cataract, pupil dilation that may mimic brain herniation) are common lightning-strike findings from the barotrauma component of the arc-induced blast wave. These injuries may be absent in a direct-strike fatality because death is rapid, but they are the primary source of morbidity in lightning-strike survivors.

Group-strike events, in which a single lightning discharge injures multiple people through ground-current dispersal or side-flash, produce a distinctive casualty pattern. The 1965 Kerala lightning mass-casualty event at Pothurpara, documented in case records at the Government Medical College Thrissur, involved fourteen people sheltering under a tree during monsoon, of whom three died immediately from direct and side-flash strikes, and eleven were injured by ground current dispersing radially from the strike point. The gradient-potential injury in ground-current events affects individuals differently based on their stance (standing presents a larger potential gradient across feet than a person lying flat), explaining why casualties at the same scene show dramatically different injury severities.

In the US, NOAA maintains the National Lightning Detection Network (NLDN) and the National Centers for Environmental Information lightning fatality database, which documents the annual average of 20-50 lightning fatalities and over 300 injuries. The database confirms that open fields, under-tree sheltering, and water-adjacent activities account for the majority of events. In Germany, the BKA annually documents 2-4 lightning fatalities, with a higher proportion of agricultural workers and outdoor athletes than the domestic electrical fatality pool, reflecting the occupational pattern.

Autopsy findings in electrical death are rarely sufficient by themselves to establish the cause and manner of death. The body examination must be integrated with scene examination, electrical circuit analysis, and, where witnesses exist, witness accounts of what the victim was doing at the moment of collapse. The cause, mechanism and manner of death classification framework is the structured tool for translating these combined findings into a court-ready opinion.

The scene investigator looks for: the faulty device, appliance, or conductor (preserved before safety personnel de-energise); arc marks (carbon deposits) on conductor surfaces at the probable contact point; the position of circuit breakers and residual-current devices (RCDs, also called ground-fault circuit interrupters, GFCIs in US terminology); any conductive fluids at the scene (water, blood, urine) that may have extended the contact area; and the victim's last known posture (victim found gripping an appliance indicates the "can't let go" tetanic-contraction mechanism).

In India, electrical-fatality investigations are shared between the police (cause-of-death determination), the local Electrical Inspector under the Indian Electricity Rules 2005 (circuit safety compliance), and the forensic medicine department (autopsy). The AIIMS forensic medicine standard operating procedure (published in the Journal of Forensic Medicine and Toxicology) recommends cross-referencing the autopsy findings with the Electrical Inspector's report before filing the cause-of-death opinion. In the UK, HSE electrical fatalities trigger a Regulation 12 RIDDOR notification and a formal HSE investigation running parallel to the Coroner's inquest. In the US, OSHA investigations of occupational electrical fatalities are required within 8 hours of notification, and the NIOSH FACE programme documents the full scene and circuit reconstruction for each case.

The forensic-pathology contribution to the reconstruction is threefold: identifying the entry and exit points to establish the current path, identifying the mechanism of death (fibrillation vs respiratory arrest vs thermal injury to cardiac muscle), and identifying any findings inconsistent with the reported circumstances (contact-point burn on a body part that the scene account does not explain, absence of entry burn suggesting the body contact with the faulty conductor was post-mortem, or the presence of pre-existing blunt-force trauma indicating a separate cause of death).