Eletrical injuries as per forensic medicine.

1. Electrocution
(Electrical Injuries)

3. MECHANISM OF INJURY
Injuries due to electricity occur by three mechanisms:
1.Direct effect of electrical current on body tissues
i.e., cellular depolarization of nerves and muscles.
2.Conversion of electrical energy to thermal energy,
resulting in deep and superficial burns.
Heat = current (I) x voltage (V) x time of contact (t)
= I x V x t
= I x (I x R) x t (from Ohm's Law)
= I2 x R x t
3.Blunt mechanical injury from lightning strike, muscle contraction,
or as a complication of a fall after electrocution.

4. Factors determining injuries:
1. Type of current
AC current is 3-5 times more dangerous than DC
current.
DC injuries are uncommon and seen in lightening
strikes and certain equipment’s.
2. Amount of current (& Voltage) and duration of
current flow.

6. 3. Resistance
Resistance is a function of the area of contact, pressure applied, and the presence of moisture. Tissues with higher
resistance tend to heat up and coagulate, rather than transmit current. Skin , bone, and fat have high resistances,
while nerves and blood vessels have lower resistances. Electricity tends to be conducted along blood vessels.
Application:
In 220 volts if the person is wet and standing barefoot then
Resistance( R ) = 1000 ohms
Current (i) = 220/1000 = 0.22 A ie 220 mA
lethal ie. Ventricular Fibrillation
In 220 volts if the person has dry skin and standing on dry rubber shoes
Resistance( R ) = 1000000 ohms
Current (i) = 220/100,000 = 0.0022 A ie 2.20 mA
produce tingling sensation

7. 4. Path of current
Death is more likely to occur if the brainstem or heart
is in the direct path of the current.
For an electric shock to occur there must be a contact
by the body with both a positive and a negative pole,
or alternatively the ‘earth’. The earth may be any
object not insulated from the ground. When the
earthing is poor as with dry and rubber shoes, carpets,
wooden floors and upstairs premise, fatal electrocution
is uncommon. If the body is well insulated it does not
conduct and no harm results.

8. Characteristics of Injuries
Local Effects : The current passes through the skin producing heat, which
causes boiling and electrolysis of tissue fluids. The skin explodes and
rolls back from the surface. A well-moistened skin may not show
electrical burn, while a thick dry skin may show well-marked electrical
burn.
The electric mark (Joule burn): It is specific and diagnostic of contact
with electricity and is found at the point of entry of the current. It is
endogenous thermal burn due to the heat generated in the body from
electricity. These marks are round or oval, shallow craters, one to three
cm. in diameter and have a ridge of skin of about one to three mm. high,
around part or the whole of their cirucmference. The crater floor is lined
by pale flattened skin. In some marks, the skin may break within or near
the margin of the crater, resembling that of a broken blister.
When contact is more prolonged, the skin in the mark becomes brown and
with further contact, there may be charring.

9. Exit Marks : These are variable in appearance, but they have some of the features of entrance
marks. There may be more damage of tissues, and they are often seen as splits in the skin at
points where the skin has been raised into ridges by the passage of current; splitting of these
ridges may be continuous or interrupted.

10. Flash or spark burn:
The intense heat which may result from flash-over produces
burns, which resemble thermal burns (exogenous burns).
In spark burn, there is an air gap between metal and
skin. Here a central nodule of fused keratin, brown or
yellow in colour is surrounded by the typical areola of
pale skin. The burns may be as small as pinpoints, or
deeply seated and contracted if contact is prolonged
or very high voltage is applied.
Very high voltage currents produce massive destruction of tissue
with loss of extremities and rupture of organs.

11. High tension electrical currents may produce multiple, small, discrete, pitted burns due to arcing from the
conductor to the body without direct contact.
Multiple burnt or punched-out lesions are produced due to the arc dancing over the body surface over
largeareas which present 'crocodile flash burns’.
Flashover often produce 'arc eye'. High amperage has an explosive blast-like effect and may produce
injuries resembling bullet, stab or incised wounds.
Electric burns or splits:
The splits are dry. hard, firm, charred, insensitive, with ragged edges. And their form is round, oval, linear,
or of irregular shape. The depth of the lesion is much greater than appears on the surface. Wrinkling of the
skin maybe found and occasionally localized oedema of a limb. Aseptic necrosis develops.

12. Systemic effects
1.Immediate death from shock.
2.CNS : Hemiplegia or paraplegia, aphasia, headache, vertigo and convulsions.
3.Eye : Cataract, optic atrophy and choroid-retinitis may occur.
4.Pulselessness, hypotensive, loss of response to external stimuli, cold and cyanotic and
without respiration – suspended animation like state may occur.
5.With recovery there may be muscular pain, fatigue and irritability.

13. Cause of Death
▪ Ventricular fibrillation (low voltage current) –
most common
▪ Less commonly paralysis of respiratory
muscles (asphyxia) and rarely due to direct
effect on brainstem.
▪ Inhibition of respiratory center, electrothermal
injury or ventricular asystole (high voltage
injury).
▪ Secondary causes: Infection , septicemia.
Secondary injuries (i.e. fall from height)

14. Postmortem Findings
Examination of Entire body, particularly the hand and feet for the evidence of
burns is important but never forget to examine the clothes.
1) External Findings
a) Face is pale / cyanosed, eyes are congested and pupils are dilated. Petechiae are seen
on eyelids and conjunctiva.
b) Rigor mortis appears early and dark blue-red postmortem staining is well developed.
c) Joule burns are the site of entry and the shape and size of the mark may corresponds
to shape and size of the source of the current but sometime may lack any visible marks
and also may show extensive charring.
2) Internal Findings
a) Brain, meninges and parenchymatous organs are congested.
b) Lungs: congested and edematous
c) Heart: Focal necrosis with variable hemorrhage and acute contraction bands in the
myocardium and conduction system
d) Petechial hemorrhages may be found along the line of passage of the current, under
the endocardium, pericardium, pleura, brain and the spinal cord

15. Medicolegal aspects
❖ Deaths are usually accidental. Suicides and homicides are rare.
➢ In homicide, plugged wire is dropped into a bucket/bathtub. There is usually no electrical
burns.
❖ Iatrogenic electrocution may lead to a charge of negligence.
❖ It is not possible to differentiate between antemortem and postmortem
electrical burns.

16. Judicial Electrocution
● Judicial Electrocution is a death penalty by
electrocution which is carried out using electric
chair.
● The condemned man is strapped to a wooden chair,
and one electrodes put on the shaved scalp and the
other on the right lower leg by the executioner.
● Alternating current of 2000V and 7 amperes for 1
min is passed through the body. After tetanic spasm
and loss of consciousness same current is passed
for the second time for 1 mins.
● Autopsy findings: An annular ring burn on the head
due to the scalp electrode and a burn on the right
calf due to the anklet, both due to electrical current
flow.

17. LIGHTNING STROKE
Lightning bolt is produced when the charged undersurface of thundercloud sends its
electrical charge to the ground. It is a direct current with potential of 20,000 amperes and
>1000 million volts.
It may injure or kill an individual by direct strike/ side flash/ conduction through another
object.
❏ Pathophysiology of Lightning injury
❏ Lightning is an unidirectional massive current impulse.
❏ Lightning is thought to be more of current phenomenon than voltage
phenomenon
❏ As current flashes over the outside of the body it can vaporize moisture on the
skin and blast apart clothes and shoes, leaving the victim nearly naked.
❏ Current from a lightning strike only flows internally for a short time, it can cause
short-circuiting of electrical systems such as the heart, respiratory centers, and
autonomic nervous system, as well as spasm of arterioles and muscles.
❏ Death is caused by high voltage direct current due to cardiopulmonary arrest.

18. Lichtenberg Flowers/ Arborescent
Markings/ Filigree burns
● Pathognomonic of lightning strike.
● Lichtenberg flowers are superficial, several
inches long, thin, irregular. tortuous, dendritic,
red marks on the skin which resembles to the
branches of a tree.
● This fern-like pattern of erythema in the skin
usually found over the shoulders or flanks.
● It is not associated with burning.
● They indicate the path taken by the discharge
and tend to follow skin creases and the long
axis of the body. It appears within 1hr and
disappears in 24-48 hrs if patient survives.

19. Others findings in lightning
● Linear burns: These vary from 3 to 30 cm in length, and 0.3 to 2.5cm width.
They are often found in the moist creases and folds of the skin. Irregular,
linear, first degree burns may follow skin creases, esp. if damp from sweating.
● Surface burns : They are true burns and occurs beneath metallic objects
worn or carried by the person, which are fused by the flash.
● Development of edema of skin at the point of entry wound in those who
survive.
● As the exit is often at the feet, shoes may be ripped apart and blown off the
foot. Articles of clothing may be found some distance from the body with the
body partly stripped which may suggest sexual assault.
● Injuries like contusion, lacerations, rupture of tympanic membrane and
organs, and spinal cord damage.
● Additional findings- singed hair, and patterned skin burn marks underneath
metal article of jewelry.

20. Medicolegal aspects
1. It’s recognition is lifesaving in the unaccompanied comatose patients
because even delayed resuscitation of lightning victims can be very
successful.
2. Death is accidental
3. Appearance is pathognomonic for injury by lightning but may closely
resemble those produced by criminal violence.

21. References:
● The Essentials of Forensic Medicine & Toxicology Dr K.S. Narayan Reddy
33rd Edition
● Review of of Forensic Medicine & Toxicology Biswas Gautam 4th edition
● www.UpToDate.com

22. Thank You!!!!!