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Electrocution Death Mechanisms
- 1. Electrocution Rijen Shrestha 30-06-2068
- 2. 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) 2
- 3. 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 3
- 4. 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 4
- 5. A typical electrical burn of the skin demonstrating charring of the center with surrounding blanching and a hyperemic rim 5
- 6. Factors affecting • Type of current (alternating or direct) • Amount of current (Amperage) • Potential difference (Voltage) • Resistance (Ohms) • Duration of event • Route of current 6
- 7. 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 7
- 8. 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=IxR Therefore, IαV Iα1 V 8
- 9. Amount of current Knight’s Forensic Pathology (2004) Amount of Current Effect 1 mA (milliAmperes) Barely perceptible tingle 16 mA (milliAmperes) Current can be grasped and released 16-20 mA (milliAmperes) Muscular paralysis 20-50 mA (milliAmperes) Respiratory paralysis 50-100 mA (milliAmperes) Ventricular fibrillations >2000 mA (milliAmperes) Ventricular standstill 9
- 10. Voltage DM Fatovich (1992) – Most deaths occur between 110 V and 380 V Z Peng and C Shikui (1995) – Electrocution rare when voltage less than 80 V B Marc et al. (2000) – Deaths may occur at low voltage if humidity reduces resistance or if contact if prolonged. 10
- 11. Voltage AC Koumbourlis (2002) • 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 11
- 12. Resistance AC Koumbourlis (2002), RK Wright and JH Davis (1980), SC Sahpira et al. (1995) • 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 resistance Exposure 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 12
- 13. Resistance JC Thompson and S Ashwal (1983), M Yamakazi et al. (1997) • Very low resistance of moist mucous membranes predisposes children to accidental exposure causing severe oro-facial injuries 13
- 14. Duration of event • Deaths have been reported with as low as 24 V when contact is maintained for several hours Route of Current LM Al-Alouisi (1990) and M Tsokos et al. (2002) • 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 14
- 15. Lightning R Blumenthal (2005) • 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 15
- 16. Lightning P Leth et al. (2004) • Deaths due to lightning are rare and are caused by high voltage direct current AC Koumbourlis(2002) • Flash-over phenomenon CJ Andrews (1992), NH Qureshi (1995) • Deaths have been reported indoors caused by lightning. 16
- 17. Mechanism of Death SC Shapira et al. (1995) • Death from electrocution may be caused by – Current itself – Secondary effects of burns – Blunt force injuries due to fall caused by current WR Lee (1965), LM Al-Alousi (1990) • Immediate mechanism of death caused by direct passage of current – Ventricular fibrillation – Respiratory paralysis – Paralysis of respiratory centers – Blunt trauma – Drowning 17
- 18. Mechanism of Death • Ventricular fibrillation – Commonest mechanism of death – Associated with passage of current though the heart – Current acts on cardiac myocytes, nodal tissue and conduction tracts 18
- 19. Mechanism of Death • 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 19
- 20. Mechanism of Death • Paralysis of respiratory centers – Occurs rarely – current passes through the brainstem – disruption of neural function due to • direct effect of current • resultant hypothermia 20
- 21. Mechanism of Death • Blunt Force Trauma – Contact with electricity may fling or throw the victim causing potentially lethal injuries or complications thereof leading to death 21
- 22. Mechanism of Death • Drowning ME Goodson (1993) – Individuals in swimming pool drowned following contact with electric shock 22
- 23. Autopsy Findings AC Koumbourlis (2000), M Tsokos et al. (2002), T Nguyen (2000) • 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 23
- 24. Skin changes 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 • 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 24
- 25. 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 25
- 26. 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. 26
- 27. Skin changes LM Al-Alousi (1990) • The entry mark shows imprint of the conductor ME Goodson (1993) • 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 27
- 28. Skin changes LM Al-Alousi (1990) • Linear markings may be seen on the skin at the level of water in case of electrocution in water • not specific to electrical deaths 28
- 29. Skin changes P Saukko and B Knight (2004) • 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” BI Resnik, CV Wetli (1996) – Arbors, fern, Lichtenberg figures or keratinographic markings. – Histologically, no significant finding other than dermal and sub- cutaneous vascular congestion 29
- 30. Series of ‘‘spark’’ lesions Deep charring of the foot Multiple punctate burns of the arm 30
- 31. Skin Changes NH Qureshi (1995) – Lichtenberg figures disappear within 24 hours if the victim survives. – Skin crease burns are more common than Lichtenberg figures LM Al–Alousi (1990) – 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. M Tsokos et al. (2002) – Cell nuclei show pyknosis and elongation with alignment. This may also be found in other types of burns and in hypothermia. 31
- 32. Irregular linear burns of the flank Histological section of an electrical burn with focal coagulative necrosis and blistering of the epidermis 32
- 33. Other organs SC Shapira (1995), M Tsokos et al. (2002) – 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 33
- 34. Other organs AC Koumbourlis (2002), T Nguyen (2000) • 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. M Tsokos et al. (2002) • Intramuscular hemorrhages are rare finding in cases of tetanic muscular contractions induced by electricity. 34
- 35. Other organs B Brinkmann et al. (1985) – Contraction bands in skeletal muscles are a regular but non-specific finding. LM Al-Alousi (1990) – High voltage electricity may cause “osseous pearls” found on the cortices of burnt bones due to marked heating. RK Wright and JH Davis (1980) – 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. 35
- 36. 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. 36
- 37. X]” © Rijen Shrestha 37
Editor's Notes
- “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, 2009Deliberate 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.
- Death results due to Direct effect of current on the heart, causing ventricular fibrillationDirect effect of current on the respiratory muscles causing respiratory paralysisEffect of current on the brainstem respiratory centers.Death may also be caused byThermal effects of the currentTrauma caused by the currentDrowning associated with exposure to electrical currentMulti-organ failure complicating primary stress due to current
- Typical findings in a case of electrocution includeClassical targetoid electrical burnsWith central charring surrounded by pallor with presence of hyperaemic rims.Adjacent nodules of burnt keratinLightning victims present withTypical fern-like patterns known as Lichtenberg figures
- Type of current (alternating or direct)Amount of current (Amperage)Potential difference (Voltage)Resistance (Ohms)Duration of eventRoute of current
- LD Budnick (1984), P Saukko and B. Knight (2004)Alternative Current is more dangerous than Direct Current at lower amperage as it is more likely to cause cardiac arrhythmias.Alternative Current also causes tetanic spasm of muscles of hand, preventing the victim from releasing his/her graspAlternative current is more likely to cause death an estimated four to six times than Direct Current
- Amperage of the current is the most important factor in electrocution.Amperage is relative to both Potential Difference (Voltage) as well as Resistance (Ohms)
- DM Fatovich (1992)Most deaths occur between 110 V and 380 VZ Peng and C Shikui (1995)Electrocution rare when voltage less than 80 VB Marc et al. (2000)Deaths may occur at low voltage if humidity reduces resistance or if contact if prolonged.
- AC Koumbourlis (2002)High voltage eletrocution may occur by arcingArcs generate extremely high temperature up to 5000o CDeath may be caused Direct effect of currentSevere burn injuriesSevere blunt trauma may be produced when victim is flung or thrown from the conductor
- AC Koumbourlis (2002), RK Wright and JH Davis (1980), SC Sahpira et al. (1995)Body tissue have variable resistance between 500 Ωand 1,000 Ω (Ohms)Bones, fat and tendon have high resistanceNerves, 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 ΩWater or sweat soaked skin may have 1,000 Ω
- JC Thompson and S Ashwal (1983), M Yamakazi et al. (1997)Very low resistance of moist mucous membranes predisposes children to accidental exposure causing severe oro-facial injuries
- Deaths have been reported with as low as 24 V when contact is maintained for several hoursThis also explains the paradox of survival with high voltage electrocution, when muscle spasms result in the victim being thrown back away from the conductor, thus dramatically decreasing the duration of current exposure. Conversely, muscle spasm causing a victim to grip a conductor may have the opposite effect by prolonging contact. LM Al-Alouisi (1990) and M Tsokos et al. (2002)Passage of current through heart or brain increases mortalityCurrent passes from point of contact to nearest earthed pointMost common route current passes is from hand to foot or hand to hand
- R Blumenthal (2005)Lightning is caused by atmospheric electricity and can produce temperatures of up to 30,000o C with current of 20,000 A and potential difference of up to 100,000,000 VDirect or Indirect Strike: A golfer standing on a course may be struck directly by lightning or indirectly through a club held in this hand.Side flash Strike: A golfer hit secondarily under a treeStep Potential: Lighting strikes the ground and the current passes from the ground through one foot and out the otherStreamer: A victim may be so highly charged during a strike that they discharge an upwards “streamer”
- P Leth et al. (2004)Deaths due to lightning are rare and are caused by high voltage direct current AC Koumbourlis(2002)Flash-over phenomenon: Passage of current from lightning over the surface of the body results in vaporisation of body surface water with a blast effect on clothing and shoes.CJ Andrews (1992), NH Qureshi (1995)Deaths have been reported indoors caused by lightning. This happens when the victim was using the telephone and the telephone wire got struck with lightning. On average, one death a year is reported in the US attributed to telephone-lightning related injuries with survivors showing a range of finding ranging from deafness due to tympanic membrane rupture, transient vertigo, ataxia, neurological deficits and convulsions.
- SC Shapira et al. (1995)Death from electrocution may be caused byCurrent itselfSecondary effects of burnsBlunt force injuries due to fall caused by currentWR Lee (1965), LM Al-Alousi (1990)Immediate mechanism of death caused by direct passage of current Ventricular fibrillationRespiratory paralysisParalysis of respiratory centersBlunt traumaDrowningB Bailey et al in 2001 found that delayed death may be due to multi-system complication following initial event.
- Ventricular fibrillationCommonest mechanism of deathAssociated with passage of current though the heartCurrent acts on cardiac myocytes, nodal tissue and conduction tracts
- Respiratory ParalysisLess common than ventricular fibrillationParalysis caused by severe contraction of respiratory muscles such as diaphragm and intercostal muscles resulting in asphyxia and deathMore commonly seen in high voltage deaths
- Paralysis of respiratory centersOccurs rarely, when the current passes through the brainstem causing disruption of neural function of the respiratory center due to direct effect of current or due to resultant hypothermia
- Blunt Force TraumaContact with electricity may fling or throw the victim away from the conductor causing potentially lethal injuries or complications thereof leading to death
- DrowningME Goodson (1993)Reported cases where individuals in swimming pool drowned following contact with electric shock
- AC Koumbourlis (2000), M Tsokos et al. (2002), T Nguyen (2000)Electrical injuries can be separated into three main groupsDirect tissue damage caused by currentThermal damage from conversion of electrical to thermal energyTraumatic injuries from muscular contractions causing bone fractures or injuries from falls
- Numerous studies have been conducted on skin changes in electrocution by 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 2002Characteristic skin lesions due to electrical current generally occurs in low voltage injuries as Joule burns at entry and exit pointsThey are present in 57 – 83 % of cases. The occurrence and severity of burns is dependent on Amount of current flow pre unit timeVoltageDuration of exposureNo burns will be produced when low voltage is passed for a short duration
- Stages of development of skin lesionsWhen skin comes into contact with current, the initial reactions include heating and vaporisation of fluid resulting in blister formationAfter the current stops, the blister collapses along with possible splitting of epidermis. The classical lesion is a 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.Spark burns occur when contact is less firm and voltage is high, resulting in arcing of current with melting of keratin into small nodules.These lesions may also be produced post mortem and it is not possible to histo-pathologically differentiate from ante mortem injuries if death occurred rapidly before a tissue inflammatory response occurred.
- LM Al-Alousi (1990)The entry mark generally shows the imprint of the conductorME Goodson (1993)The pattern of electrical burns may indicate torture or homicideNo marks on the skin may be seen if the contact point was broadWater considerably reduces resistance and also cools the skin preventing injury
- LM Al-Alousi (1990)Linear markings may be seen on the skin at the level of water in case of electrocution in water but they are not specific to electrical deaths
- P Saukko and B Knight (2004)MetallizationTissue anions combine with metal of an electrode to form metallic salts that may be seen on the skin surface. If an arc forms, the skin may be coated with a thin layer of vaporized metal. 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. There may also be multiple arcs causing numerous spark burns resulting in “crocodile skin” appearanceME Goodson (1993)High voltage due to lightning may also produce arbors, fern, Lichtenberg figures or keratinographic markings. These are multiple brick-red to brown linear macules in a ferning pattern on the skin possibly caused by heat denaturation of red-blood cells resulting in a distinctive pattern of hemolysis.Histologically they present with no significant finding other than dermal and sub-cutaneous vascular congestion
- NH Qureshi (1995)Lichtenberg figures disappear within 24 hours if the victim survives. Skin crease burns are more common than Lichtenberg figuresConjunctival and internal petechiae have been described by P. Leth et al and B. Karger et al.Histological findings are due to thermal effects with no pathognomic lesions.LM AlousiThere is often an 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.M Tsokos et al.Cell nuclei show pyknosis and elongation with alignment. This may also be found in other types of burns and in hypothermia.
- SC Shapira (1995), M Tsokos et al. (2002)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
- The investigation of deaths possibly due to electrocution requires a team approach with a clear description of the death scene, including photographic documentation of the body, scene and any nearby electrical devices or conductors. An analysis of the electrical circuitry within, and sometimes connecting to, the building where the victim was found is required in addition to examination of any equipment that was near the body by individuals fully qualified in electrical assessment [6]. A complete autopsy with careful examination of clothing and body surfaces for subtle electrical burns is then required. Clothes may show burns corresponding to contact with metallic conductors and torn clothing with burned shoes may implicate lightning [13, 28]. Examination of the body for evidence of underlying natural diseases such as cardiovascular conditions is also important, as these may have predisposed the victim to coming in contact with live circuitry, or may have reduced the victim’s capacity to survive an electric shock.The most difficult cases are often those where a body is presented to autopsy with a history of ‘‘collapse’’ or being ‘‘found dead’’, with no indication that electrocution is a possibility. It may be necessary to ask police to return to a scene and check for electrical devices if electrocution is suspected. A history of screaming, swearing, or shouting followed by collapsemay indicate electrocution. Early or partial development of rigor mortis may also indicate electrocution as tetany from electrical current may accelerate the development of rigor [6]. Careful examination of all body surfaces, including the flexor surfaces of the fingers, with photography and histological sampling of possible electrical burns is required.