Electrocution and Lightning

Dr. M Vidanapathirana,

MBBS, DLM, MD, MA, MFFLM (UK)

Senior lecturer

Consultant in Forensic Medicine

Electrical injuries can be Trivial or fatal Observable or inconspicuous or absent

Voltage is increased for transmission over long distances. USA -100,000V In SL- 33,000V

At industries – 480V At houses

USA –at the main switch240v and at wall -120V SL- 240V

High voltage –more than 1000v Low voltage – less than 600v

AC – 60 Hz DC-

battery current- Practically not encountered (rarely can cause

death of person with IHD due to spasms or VF)

High voltage electrocution – extensive burns, therefore, little difficulty for

forensic pathologists for diagnosis

But serious problem in Low voltage household AC current- die with little

or no visible injury (35-50% no electrical burns) Lightning – usually die with little or no injuries

(though it is high voltage, it affects for extremely short duration)

DEATHS due to LOW VOLTAGE ELECTROCUTION (DOMESTIC)

1. Incidence SL - Not frequent. USA- 1000 deaths /year (lightning -150 deaths/y)

Time of the year – more when hot Less clothes and barefooted, More sweat and less resistance

2. Circumstances1) Accidental- most.

domestic accidents, while repairing electrical appliances etc. Immersion heater

Construct by the inmates of prisons Immerse 2 forks with prong end up Then, electrical cord is connected.

2) Suicidal – rare, usually by electricians or engineers. Sometimes, special home made device is used.

eg. Live wire is applied around the wrist. electrocution in the bathtub.

3) Homicidal- usually in bathtubs.

4) Sexual – electrode is fixed at anus or penis.

5) Judicial (Electrical chairs)- as capital punishment started in New York in 19th century. Still used in some states of USA. 2000v with 10 amp PM- marked, burns on skin and tissues.

3 elements required simultaneously for electrocution

Electrical source Current pathway through the body Grounding (eg. Bare feet, metal pipes etc)

No harm if well insulated from ground, eg. Birds sit on high tension wires with no effect.

Effects of current depends on the amount of amperes.

If 1mA- felt (tingling of the fingers) If 5mA-

tetanic contractions and hence grab the power conductor (no-let-go threshold),

hence increase the duration of contact and die. Old trip switches cut off at 30mA. But modern GFCI (ground fault circuit interrupters) cuts off well below

5mA 15mA- control over muscles is lost If 50mA-

loss consciousness, severe muscles contractions, hence can lead to traumatic asphyxial and

even fractures in bones. eg. Bilateral scapular fractures, Bilateral humeral fractures, Bilateral neck

of femur fractures, T12- L1 fractures.) If 70mA- fatal

Protection of the equipment- Circuit breakers or fuses

Protects only the equipment. Not the people. Prevent current of equipment reach high (more

than 30mA) Current reach high by way of

Overloads (when too may appliances are plugged into a circuit)

Short circuits (when current bypasses the normal circuit and flow directly to the ground)

If not disconnected by circuit breakers or fuses, due to high current flow, leads to intense heat and may cause fire. It cuts off when the current reaches higher than 30mA.

Circuits are grounded

by a copper rod driven into earth. When there is a leak, this very low resistance track

would take the current to the earth rapidly than via body and the enhance current would trip off the breakers or fuses.

But it needs 30mA to off the trips. Unfortunately people get tetanic spasms of muscles and hold on effect well below 30mA (at 5mA) and can die.

So now we use GFCI (Ground Fault Circuit Interrupter) or GFC because they off well below 5mA.

Grounded electrical equipment Most electrical equipment are grounded. If black hot live wire, short circuits to the Metal cover of

an equipment (eg. Electric hammer), and the metal cover becomes electrified, it is grounded to the earth via the green wire.

White neutral wire is also grounded. Electrocution involving a grounded equipment, 2

defects should be there, Defect of the insulation of the live wire-When the live

wire is connected to the grounded casing it is called a Charged equipment .

Defect in the ground circuit

Non-grounded electrical equipment Certain appliances should not be grounded. Eg. Metal-cased appliances with exposed heating

elements eg. Toaster or immersion heater Because a person can get electrocuted if contact with

heating element and the grounded metal casing

Protection for us from electrocution

GFI (Ground fault interrupters) or GFCI (Ground fault circuit interrupters) Even at 5mA current for 1/40 of a second, they

disconnect. Double insulated equipment. Casing is

plastic.

After fatal electrocutions, usually the victim remains conscious and speak or move for several seconds. Eg. ‘Ayyo I got electrocuted’.

Electrocution should be suspected especially if

Person is grounded Exposed to a potential electrical source If cries out or utters an ‘expletive’ prior to

collapsing

Predisposing factors of domestic electrocution

1. electrical appliance attached to electrical circuit, 2. AC> DC (6:1) 3. Voltage –

in high voltage electrocution- 1000- 33000V. More and severe injuries. Skin resistance does not matter.

In low voltage (domestic) electrocution - 240 V, less injuries compared to high voltage. Fatality depends on the amount of Amperes.

4. Amperes (I) – most important factor to cause death. If increase- more lethal, if less- safe V = IR , I = V/R , V= 240V (constant) Therefore I depends on R, if R increases, I decreases.

5. Resistance (R)– if increase-

increase local injury due to more heat generation, but decrease the entry of ampere amount and decrease fatality.

If decrease- decrease local injury due to less heat generation but increase the entry of amperes and hence the fatality.

6. Duration of contact If prolong- severe injuries If short- less injuries

7. Surface area of contact. If increased – reduce resistance (eg. Wet surface), less injuries If small- more resistance, more heat production and hence the injuries.

8. Pathway of current through the body. a. hand to hand or b. hand, heart and feet, c. hand, chest wall and feet, d. hand brain and scalp etc

Place of the incidents

50% - at home- biting of an extension cord by children. Damaged or bare wires – accidental

50% of home incidents occur while bathing Equipment can fall into bath tub Hair dryers are now equipped with GFCI

At hospital- from ECG electrodes. At working place- partly missing of the friction tape used

to cover a defect in the insulation

When current flows through the body, it takes the shortest and least resistance pathway.

If Hand to head –current goes through brain – respiratory centre paralysis (can die immediately),

If Hand to leg – current goes through heart- ventricular fibrillation (need few seconds of contact to die), loose

consciousness in 10 –15 seconds, as the brain has oxygen reservoir for 10- 15 seconds, with out cardiac output. Therefore can cry out for help or shout, some times can disconnect by him.

If Hand to hand – current goes through chest wall muscles, resulting continuous contractions or spasms of inter costal muscles

and diaphragm - leading to traumatic asphyxia (need several minutes of contact to die)

Clinical features Depends on

amount of Ampere and the pathway within the body, Complications

Amount of Amperes depend on

1. Skin resistance- Insulating effect of skin

eg. Dry thick skin (palm or sole) - 1 million ohms.Dry normal skin – 100,000 ohms.Moist thick skin (palm or sole) – 1000 ohms,Moist normal skin – 100 ohms.

2. Also depends on clothing-eg, rubber gloves or boots act as insulators, hence protective.

3. Complications

1. Blood and blood vessels less resistance Heat of the current cause

Break up RBC and WBC Activate platelets Damage endothelium of Blood vessels

If survive Can cause thrombosis of the BVs eg. Right brachial A.

2. Bones If high voltage- fractures due to forceful muscles

contractions

Mechanisms of death- 1. If current travel through brain/ spinal cord

brain centres paralysed and die. if interferes with respiration, asphyxial death

2. If current travel through heart VF and cardiac arrest, even with ventricular fibrillation and die

even with 120v for split of a second. 3. If current travel through the chest wall

Direct paralysis of chest muscles – asphyxial death (traumatic asphyxia)

PM findings

Usually reveals no specific results some times can cause cadavaric spasm

(instantaneous rigor mortis) of affected body part.

Examination of clothing- burns

Post-mortem findings Depend on ........ 1. Thermal effect

( mainly due to resistance( R) – cause local burns. Local burns depend mainly on resistance. Also on surface area and duration of contact.

2. Electrical effect (mainly due to current (Amperes) –

cause death

Entry wounds1. Joule burns- contact is needed.

Due to cooking effect on tissues. Elevated crater with charred centre. It is the collapsed blister.

May be patterned entry wound. Threads of a bulb can be found branded on the entry.

Surrounded by Pale peripheral halo and further surrounded by red halo. Blood pushed out due to heat.

2. Spark burns – contact is not needed. If there is a gap between the conductor and the body, there can be arcing

3. Odour - Fresh burns have a characteristic odour - burnt cork.

4 Arcing of eyes and face– it is erythema of the face with burns of the eye lashes. (this is due to radiant heat released from current. Radiant heat usually causes only erythema of the skin but no singeing of hair. The eye lashes are singed due to their erected posture).

Severe thermal denaturation of the collagen- stains blue with haematoxylin.

Joule and spark burns

Internal findings Pulmonary and cerebral oedema (increase

weight) - due to VF or asphyxiation. Visceral petechiae- asphyxiation Muscle damage and fractures- Some times

muscle contractions could lead to muscle damage and fractures.

Exit wound- Usually a split. Usually on soles. (if the exit site is wet, there may be no exit injury)

PM electrical burns

Indistinguishable from PM electrical burns. Charred centre, surrounded by pale peripheral

zone and surrounded by red halo. Red halo is due to due to displaced blood from

vessels due to heat. Differentiated by scene, circumstances and

witness but not by autopsy.

Investigations

1. Light Microscopy (histopathology)- Epidermis and dermis- Swiss cheese appearance. Micro-blisters of the epidermis is typical of electrical burns. Basal epidermal cells – nuclear streaming. Thin elongated and parallel to each other (palisading appearance).- this streaming is characteristic of electrical burns.

2. Dissecting microscopy or SEM (scanning electron microscopy) - small metal pieces or debris from wire can be seen deposited in the wound.

3. Histochemical colour tests to identify the conductor With copper produce purplish colour. Iron produce blue

colour

4. Can trace the potential electrical conductor – by doing DNA of hair or un-charred shreds of epidermis found on it and compare it with the victim.

Scene visit Multidisciplinary approach

at scene examination by an electrical

engineer is the best. Fire fighters should be

involved. Photographed X-ray the cords and plugs

to demonstrate the defects. If not done a proper scene

visit, the rate of wrong assumptions are higher.

At the scene, look for, Potential electrical source Charged conductor breakers/ fuses or GFI Whether outlets were properly wired- checked by outlet checker . All portable electrical equipment, extension cords, adapters, should

be collected and submitted for examination and reporting Check the grounding system- if not properly working, current

passes through the victim. Examination may alter the equipment and therefore, each step

should be documented and photographed. Examination of the equipment

Dismantled for examination May see effects of arcing on the metal- grooving, beads of

melted metal, and carbon charring. Defect of the circuit can be seen. Eg. Defect in the insulation of

hot or neutral wire.

DC current burns From third rail of rapid transit tracks. When

urinating on the third rail.

High voltage electrocutions- Contact is not needed. Can injure by arcing. Circumstances

1. Downed power lines as in storms 2. Climbing up on electrical utility poles 3. When using tall metal ladders, hoists, cranes etc

Post mortem features- Almost all have a visible electrical burn. 1. Entry wound- If contact - joule burn

Crater is produced. It is charred. Large, irregular and surrounded by a pale areola.

On bones- charred centre indicates the size of the wire and the halo around it is due to displacement of marrow and blood due to heat.

If there is a gap – a) Spark or arc burns – crocodile skin. Circular multiple

discrete crater like spark burns due to dance over the body surface.

b) Flash burns – rosette appearance.c) Severe burns- if prolonged exposure.

2ry burns by cloth burns.

If Thrown away – Evidence of fall can be there. head injury. Blast effect – rupture of organs. Muscles contractions can lead to fractures. Hyperthermia also can occur.

2. Exit – Split

Cause of death in electrocution deaths

1. Electrocution 2. Head injury following fall 3. burns

If no external injuries (negative autopsy) especially with low voltage electrocution, still can diagnose the COD as electrocution on Circumstances, Scene visit History and Examination of the electrical conductor

Injuries due to Lightening

Definition -

Natural, high voltage direct current (DC) in the atmosphere is called lightning or lightning flash.

Circumstances

Usually with thunderstorms Sometimes when it is not raining. Lightning is attracted to

Trees, Metal fences, Gates, Tall light poles, Power lines Open areas such as grounds, swimming pools (unless

properly grounded) When using Telephone or electrical appliances such as

computers, TV, power tools Having shower or baths

Protection by hardtop vehicles.

Mechanism of lightning

Develop a large negative charge on the under surface of the clouds.

Earth is positively charged. Electrical arcs are caused.

Start as a slow leader stroke from clouds to earth. Then a pilot stroke runs up from earth to meet the

leader stroke. When they meet, rapid and powerful return stroke

occurs. Therefore, arcs move in both directions

Power higher. less injuries Injuries differ significantly from high tension

Voltage- 10-100 mn V Current 10,000-100,000A Temperature- 15,000-50,000F

But the duration is extremely small. (1/10,000sec), Due to phenomenon called flashover, majority of energy

travels over the surface of the victim’s body therefore,

no burns at all or very small burns- pin head sized or scratches like,

minor singeing of hair Pinhead sized exits

Mechanism of Injury Direct strike-

current strikes directly, affect metal objects worn, Side flash or splash-

current jump ricochets from adjacent object to the victim and transient fern-like (Lichtenberg/ arborescent burns) marking may be seen. May remain or disappear with time, associated with singing of adjacent hair. Haemolysis due to heat along the BVs may be the cause

Ground strike- current conducts from ground to the victim, can enter through

one leg and exit through the other. Contact strike-

when in contact with a electrical conductor Blast effect- injuies

Arborescent burns

Fatality

Fatality is less than 50% Most survive-

CPR and artificial ventilation should be continued until onset of Rigor mortis.

Strikes on airplanes – little or no damage Sometimes- ignition and explosion of fuel

compartment, temporary blinding of pilots, interfere with electrical system.

Rubber boots and shoes- no protection against lightning

PM findings

1. Metal Melting of iron objects – eg coins, wrist watches, ornamentsMagnetization of objects- eg coins, wrist watches, ornamentsMetallization- small metal particles travel into the body with current. (could be demonstrated by histopathology)

2. Blast wave effects- blast of shoes, tearing of clothes etc tearing of internal organs such as lungs, bowels etc.

3. Burns. Could be 1. Flame burns2. Linear burns – along skin creases. Eg. on palm. Due to dampness on creases.3. Fern like/ arborescent burns- as this is transient it should be photographed as soon as possible in live cases.

Explosive effect can cause rupture of eardrums. Multiple foci of SAH Throws the victim away, and fall May rip clothing and shoes. Clothes can get

shredded, or burnt

6. Scene findings-

Outdoors, During thunderstorms Dead animals. Burnt buildings and trees.

Thank You !