Transcript Electrocution and Lightning

Electrocution and Lightning
Dr. M Vidanapathirana,
MBBS, DLM, MD, MA, MFFLM (UK)
Senior lecturer
Consultant in Forensic Medicine
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Electrical injuries can be
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Voltage is increased for transmission over long
distances.
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Trivial or fatal
Observable or inconspicuous or absent
USA -100,000V
In SL- 33,000V
At industries – 480V
At houses
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USA –at the main switch240v and at wall -120V
SL- 240V
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High voltage –more than 1000v
Low voltage – less than 600v
AC – 60 Hz
DC
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battery currentPractically not encountered (rarely can cause
death of person with IHD due to spasms or VF)
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High voltage electrocution –
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extensive burns, therefore, little difficulty for
forensic pathologists for diagnosis
But serious problem in
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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
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SL - Not frequent.
USA- 1000 deaths /year (lightning -150 deaths/y)
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Time of the year – more when hot
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Less clothes and barefooted,
More sweat and less resistance
2. Circumstances
1) Accidental- most.
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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,
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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 –
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electrode is fixed at anus or penis.
5) Judicial (Electrical chairs)- as capital punishment
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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
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Electrical source
Current pathway through the body
Grounding (eg. Bare feet, metal pipes etc)
No harm if well insulated from ground,
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eg. Birds sit on high tension wires with no effect.
Effects of current depends on the
amount of amperes.
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If 1mA- felt (tingling of the fingers)
If 5mA
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15mA- control over muscles is lost
If 50mA
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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
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 equipmentCircuit breakers or fuses
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Protects only the equipment. Not the people.
Prevent current of equipment reach high (more
than 30mA)
Current reach high by way of
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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
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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.
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Grounded electrical equipment
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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,
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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
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Non-grounded electrical equipment
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Certain appliances should not be grounded.
Eg. Metal-cased appliances with exposed heating
elements eg. Toaster or immersion heater
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Because a person can get electrocuted if contact with
heating element and the grounded metal casing
Protection for us from electrocution
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GFI (Ground fault interrupters) or GFCI (Ground
fault circuit interrupters)
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Even at 5mA current for 1/40 of a second, they
disconnect.
Double insulated equipment. Casing is
plastic.
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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
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Person is grounded
Exposed to a potential electrical source
If cries out or utters an ‘expletive’ prior to
collapsing
Predisposing factors of
domestic electrocution
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1. electrical appliance attached to electrical circuit,
2. AC> DC (6:1)
3. Voltage –
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in high voltage electrocution- 1000- 33000V.
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In low voltage (domestic) electrocution - 240 V,
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More and severe injuries. Skin resistance does not matter.
less injuries compared to high voltage.
Fatality depends on the amount of Amperes.
4. Amperes (I) –
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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.
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5. Resistance (R)–
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if increase
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If decrease
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If prolong- severe injuries
If short- less injuries
7. Surface area of contact.
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decrease local injury due to less heat generation
but increase the entry of amperes and hence the fatality.
6. Duration of contact
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increase local injury due to more heat generation,
but decrease the entry of ampere amount and decrease fatality.
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.
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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
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50% - at home
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50% of home incidents occur while bathing
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biting of an extension cord by children.
Damaged or bare wires – accidental
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.
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If Hand to head –current goes through brain –
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If Hand to leg – current goes through heart
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respiratory centre paralysis (can die immediately),
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,
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resulting continuous contractions or spasms of inter costal muscles
and diaphragm - leading to traumatic asphyxia (need several
minutes of contact to die)
Clinical features
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Depends on
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amount of Ampere and
the pathway within the body,
Complications
Amount of Amperes
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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.
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2. Also depends on clothing-eg, rubber gloves or boots act as
insulators, hence protective.
3. Complications
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1. Blood and blood vessels
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less resistance
Heat of the current cause
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If survive
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Break up RBC and WBC
Activate platelets
Damage endothelium of Blood vessels
Can cause thrombosis of the BVs eg. Right brachial A.
2. Bones
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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
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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
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Direct paralysis of chest muscles – asphyxial death (traumatic
asphyxia)
PM findings
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Usually reveals no specific results
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some times can cause cadavaric spasm
(instantaneous rigor mortis) of affected body
part.
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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 wounds
1.
Joule burns- contact is needed.
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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.
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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).
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Severe thermal denaturation of the collagen
stains blue with haematoxylin.
Joule and spark burns
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Internal findings
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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
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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. Microblisters 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
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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
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Multidisciplinary approach
at scene
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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.
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At the scene, look for,
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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.
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DC current burns
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From third rail of rapid transit tracks. When
urinating on the third rail.
High voltage electrocutions
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Contact is not needed. Can injure by arcing.
Circumstances
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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 featuresAlmost 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.
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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.
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2ry burns by cloth burns.
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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
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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
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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
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Usually with thunderstorms
Sometimes when it is not raining.
Lightning is attracted to
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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
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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
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Injuries differ significantly from high tension
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But
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Voltage- 10-100 mn V
Current 10,000-100,000A
Temperature- 15,000-50,000F
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,
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no burns at all or very small burns- pin head sized or
scratches like,
minor singeing of hair
Pinhead sized exits
Mechanism of Injury
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Direct strike
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Side flash or splash
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current conducts from ground to the victim, can enter through
one leg and exit through the other.
Contact strike
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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
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current strikes directly, affect metal objects worn,
when in contact with a electrical conductor
Blast effect- injuies
Arborescent burns
Fatality
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Fatality is less than 50%
Most survive
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CPR and artificial ventilation should be continued
until onset of Rigor mortis.
Strikes on airplanes – little or no damage
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Sometimes- ignition and explosion of fuel
compartment, temporary blinding of pilots, interfere
with electrical system.
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Rubber boots and shoes- no protection
against lightning
PM findings
1. Metal
Melting of iron objects – eg coins, wrist watches, ornaments
Magnetization of objects- eg coins, wrist watches, ornaments
Metallization- 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 burns
2. 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.
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Explosive effect can cause
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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-
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Outdoors,
During thunderstorms
Dead animals.
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Burnt buildings and trees.
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Thank You !