ElectrocutionRijen Shrestha

30-06-2068

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Introduction• Definition:

“Death brought about by electricity”– The Oxford Pocket Dictionary of Current English, 2009

• Death, murder or a sudden accident caused by an electric shock.– Merriam-Webster Dictionary of the English Language, 2009

• Deliberate execution by means of an electric shock, such as an electric chair; "electrocution" is a portmanteau for "electrical execution". It has never been proven as cause of death.

– Electrocution may be due to • Low Voltage (<1000 Volts)• High Voltage (>1000 Volts)• Lightning (up to 100,000,000 Volts)

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Mechanism

• Death results due to – Direct effect of current on the heart, causing ventricular

fibrillation– Direct effect of current on the respiratory muscles causing

respiratory paralysis– Effect of current on the brainstem respiratory centers.

• Death may also be caused by• Thermal effects of the current• Trauma caused by the current• Drowning associated with exposure to electrical current• Multi-organ failure complicating primary stress due to current

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Typical findings

• Classical targetoid electrical burns– With central charring surrounded by pallor with

presence of hyperaemic rims.– Adjacent nodules of burnt keratin

• Lightning victims present with– Typical fern-like patterns known as Lichtenberg

figures

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A typical electrical burn of the skin demonstrating charring of the center with surrounding blanching and a hyperemic rim

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Factors affecting

• Type of current (alternating or direct)• Amount of current (Amperage)• Potential difference (Voltage)• Resistance (Ohms)• Duration of event• Route of current

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Type of current

LD Budnick (1984), P Saukko and B. Knight (2004)

• Alternative Current more dangerous than Direct Current• more likely to cause cardiac arrhythmias.

• tetanic spasm of muscles of hand, preventing the victim from releasing his/her grasp

• four to six times more likely to cause death

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Amount of current

• Amperage of the current is the most important factor in electrocution.

• Relative to both Potential Difference (Voltage) as well as Resistance (Ohms)

V = I x RTherefore,

I α V I α 1d V

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Amount of Current Effect1 mA (milliAmperes) Barely perceptible tingle

16 mA (milliAmperes) Current can be grasped and released16-20 mA (milliAmperes) Muscular paralysis20-50 mA (milliAmperes) Respiratory paralysis

50-100 mA (milliAmperes) Ventricular fibrillations>2000 mA (milliAmperes) Ventricular standstill

Knight’s Forensic Pathology (2004)

Amount of current

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Voltage

– Most deaths occur between 110 V and 380 V

– Electrocution rare when voltage less than 80 V

– Deaths may occur at low voltage if humidity reduces resistance or if contact if prolonged.

DM Fatovich (1992)

Z Peng and C Shikui (1995)

B Marc et al. (2000)

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Voltage

• High voltage electrocution may occur by arcing• Arcs generate extremely high temperature up to

5000o C• Death may be caused – Direct effect of current– Severe burn injuries– Severe blunt trauma may be produced when victim is

flung or thrown from the conductor

AC Koumbourlis (2002)

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Resistance

• Body tissue have variable resistance between 500 Ω and 1,000 Ω (Ohms)– Bones, fat and tendon have high resistance– Nerves, blood, mucous membrane and muscles have low

resistanceExposure of different parts of body to same voltage will produce different amperages.– Skin has moderate resistance variable based on thickness and dampness.• Dry skin can have up to 100,000 Ω• Water or sweat soaked skin may have 1,000 Ω

AC Koumbourlis (2002), RK Wright and JH Davis (1980), SC Sahpira et al. (1995)

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Resistance

• Very low resistance of moist mucous membranes predisposes children to accidental exposure causing severe oro-facial injuries

JC Thompson and S Ashwal (1983), M Yamakazi et al. (1997)

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Duration of event• Deaths have been reported with as low as 24 V

when contact is maintained for several hours

• Passage of current through heart or brain increases mortality

• Current passes from point of contact to nearest earthed point

• Most common route current passes is from hand to foot or hand to hand

Route of CurrentLM Al-Alouisi (1990) and M Tsokos et al. (2002)

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Lightning

• Lightning is caused by atmospheric electricity – temperatures of up to 30,000o C – current of up to 20,000 A– potential difference of up to 100,000,000 V

– Direct or Indirect Strike– Side flash Strike– Step Potential– Streamer

R Blumenthal (2005)

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• Deaths due to lightning are rare and are caused by high voltage direct current

• Flash-over phenomenon

• Deaths have been reported indoors caused by lightning.

LightningP Leth et al. (2004)

AC Koumbourlis(2002)

CJ Andrews (1992), NH Qureshi (1995)

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Mechanism of Death

• Death from electrocution may be caused by – Current itself– Secondary effects of burns– Blunt force injuries due to fall caused by current

• Immediate mechanism of death caused by direct passage of current – Ventricular fibrillation– Respiratory paralysis– Paralysis of respiratory centers– Blunt trauma– Drowning

SC Shapira et al. (1995)

WR Lee (1965), LM Al-Alousi (1990)

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• Ventricular fibrillation– Commonest mechanism of death– Associated with passage of current though the

heart– Current acts on cardiac myocytes, nodal tissue and

conduction tracts

Mechanism of Death

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• Respiratory Paralysis– Less common than ventricular fibrillation– severe contraction of respiratory muscles such as

diaphragm and intercostal muscles– More commonly seen in high voltage deaths

Mechanism of Death

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• Paralysis of respiratory centers– Occurs rarely– current passes through the brainstem – disruption of neural function due to • direct effect of current • resultant hypothermia

Mechanism of Death

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• Blunt Force Trauma– Contact with electricity may fling or throw the

victim causing potentially lethal injuries or complications thereof leading to death

Mechanism of Death

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• Drowning

– Individuals in swimming pool drowned following contact with electric shock

Mechanism of Death

ME Goodson (1993)

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Autopsy Findings

• Electrical injuries can be separated into three main groups– Direct tissue damage caused by current– Thermal damage from conversion of electrical to

thermal energy– Traumatic injuries from muscular contractions

causing bone fractures or injuries from falls

AC Koumbourlis (2000), M Tsokos et al. (2002), T Nguyen (2000)

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Skin changes

• Characteristic skin lesions • low voltage injuries (Joule burns) at entry and exit points

• Present in 57 – 83 % of cases. • The occurrence and severity of burns is dependent on

• Amount of current flow per unit time• Voltage• Duration of exposure

• No lesions when low voltage passed for short duration

AC Koumbourlis in 2002, LM Al-Alousi in 1990, RK Wright and JH Davis in 1980, P Leth et al. in 2004, B Karger et al in 2002

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Skin changes

• Stages of development of skin lesions– Blister formation– Classical lesion – small, circumscribed, crater-like

indurated lesion with a charred gray or black center surrounded by a zone of pallor caused by arteriolar spasm and coagulative necrosis. This may be surrounded by a zone of hyperaemia with presence of vesicles.

– Keratin nodules formation– These lesions may also be produced post mortem

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Classical lesionSmall, circumscribed, crater-like indurated lesion with a charred gray or black center surrounded by a zone of pallor caused by arteriolar spasm and coagulative necrosis. This may be surrounded by a zone of hyperaemia with presence of vesicles.

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Skin changes

• The entry mark shows imprint of the conductor

• Pattern of electrical burns may indicate torture or homicide

• No marks seen if the contact point was broad• Water considerably reduces resistance and also

cools the skin preventing injury

ME Goodson (1993)

LM Al-Alousi (1990)

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Skin changes

• Linear markings may be seen on the skin at the level of water in case of electrocution in water

• not specific to electrical deaths

LM Al-Alousi (1990)

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• Metallization– Brass or copper electrodes cause a bright green colour. – Metal residue can be tested by chemical testing or by scanning

electron microscope.– High voltage electrocution may cause severe burning with deep

charring. – “crocodile skin”

– Arbors, fern, Lichtenberg figures or keratinographic markings. – Histologically, no significant finding other than dermal and sub-

cutaneous vascular congestion

Skin changesP Saukko and B Knight (2004)

BI Resnik, CV Wetli (1996)

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Series of ‘‘spark’’ lesions Deep charring of the foot

Multiple punctate burns of the arm

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– Lichtenberg figures disappear within 24 hours if the victim survives.

– Skin crease burns are more common than Lichtenberg figures

– Abrupt transition from normal to abnormal cells with micro-vescicle formation and separation of cells of lower epidermis as well as coagulative necrosis extending into the dermis.

– Cell nuclei show pyknosis and elongation with alignment. This may also be found in other types of burns and in hypothermia.

Skin ChangesNH Qureshi (1995)

LM Al–Alousi (1990)

M Tsokos et al. (2002)

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Irregular linear burns of the flank

Histological section of an electrical burn with focal coagulative necrosis and blistering of the epidermis

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Other organs

– Heart may show scattered foci of myocardial necrosis with sub-endocardial hemorrhage and contraction bands. These are non-specific findings.

– Vascular injuries may result in damaged vessel intima and media that may lead to subsequent thrombosis or rupture or aneurysm if the individual survives.

– CNS findings are non-specific with reports of cerebral oedema, petechial hemorrhages, demyelination and cellular vacuolisation

SC Shapira (1995), M Tsokos et al. (2002)

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Other organs

• Soft tissue and visceral injuries may result from fall due to electricity causing muscular contractions.

• Long bone fractures, vertebral crush fractures and joint dislocations may be caused directly by muscular contractions or secondarily from fall.

• Intramuscular hemorrhages are rare finding in cases of tetanic muscular contractions induced by electricity.

AC Koumbourlis (2002), T Nguyen (2000)

M Tsokos et al. (2002)

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Other organs

– Contraction bands in skeletal muscles are a regular but non-specific finding.

– High voltage electricity may cause “osseous pearls” found on the cortices of burnt bones due to marked heating.

– Early or partial development of rigor mortis may indicate electrocution since it may be caused acceleration development of rigor mortis following tetanic contractions induced by electrical current.

B Brinkmann et al. (1985)

LM Al-Alousi (1990)

RK Wright and JH Davis (1980)

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Conclusion

• Team approach with a clear description of the death scene, including photographic documentation of the body, scene and any nearby electrical devices or conductors.

• A complete autopsy with careful examination of clothing and body surfaces for subtle electrical burns is required.

• Clothes may show burns corresponding to contact with metallic conductors and torn clothing with burned shoes may implicate lightning.

• Careful examination of all body surfaces, including the flexor surfaces of the fingers, with photography and histological sampling of possible electrical burns is required.

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© Rijen Shrestha