electrocution 16

7/24/2019 Electrocution 16

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Electrocution

16Deaths caused by electrocution are infrequent. Virtually all are accidents,

with suicides rare and homicides even rarer. These deaths involve both

low- voltage (6!! V" and high-voltage (#6!!$%&! V" currents. They

virtually always involve alternating currents, because direct current is

used less. 'n addition, humans are four to si times as sensitive to

alternating currents as to direct. )lternating currents between *+ and 1&!

cycles er s have the greatest lethality. 'n the .., alternating current is

generated at a 6!-/0 frequency in 2uroe at &!-/0.

)merage, or the amount of current flow, is the most imortant

factor in electrocution. 't is directly related to the voltage and inversely

related to the resistance. Voltage is a measure of the electromotive force

and ohms are the resistance to the conduction of electricity. This is

eressed in the formula3

) 4 V5

esidential voltage in the .. is aroimately 11!$17! V from line

to ground. /igh-voltage lines in suburban and urban areas are

aroimately

%&!!$8!!! V line to ground with transcontinental high-tension lines

1!!,!!!

V or greater. 9or electrocution from low-voltage (11!$17! V" household

current, there must be direct contact with the electrical circuit, with death

rimarily caused by ventricular fibrillation. 'n high-voltage accidents,

direct contact with the wire is not necessary. )s the body aroaches the

high- voltage line, an electric current (arc" may :um from the line to the

body. Death from high-voltage electrocution is usually caused by either the

electrothermal in:ury roduced by the current, or resiratory arrest. The

temerature generated by an arc current can be as high as ;!,!!!


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Table 16.1 The Distance An Electric Arc Can Jump*

Voltage Distance =urrent =an )rc

1,!!! few mm&,!!! 1 cm

7!,!!! 6 cm

;!,!!! 1* cm

1!!,!!! *& cm

B as given by omogyi and Tedeschi1

1!! ohms.7 Aith high-voltage currents, s>in condition lays no significant

role in resistance to electrocution.

Mechanism of Death

)merage is the most imortant factor in electrocution. ince voltage is

usually constant, the main factor in determining the amount of amerage

that enters the body is the resistance, as eressed in ohms. The minimal

amount of amerage ercetible to a human as a tingle is 1 m) (!.!!1 )".

) current of & m) will roduce tremors of the musculature while 1&$1%

m) will cause contracture of the muscles, which revents release of the

electrical source. This latter current is the ?no-let-go@ threshold. )t &! m),

there is contracture of all muscles, resiratory aralysis and death if the

current is sustained. Ventricular fibrillation occurs at currents between %&

and 1!! m). 2tremely high currents, C1 ) and higher, do not cause

ventricular fibrillation, but rather ventricular arrest. 'f the current is then

turned off, and there is no significant electrothermal in:ury to the heart,

the heart should begin to beat normally.

Ahen electrical current enters the body, it runs from the oint of

contact to the oint of grounding, following the shortest ath. ost

commonly, the ath is from hand to foot or hand to hand. The timenecessary for a current to cause death deends on the amerage. Thus, in

very low-amerage electrocutions, where death is caused by aralysis of

the muscles with secondary ashyia, rolonged contact, (i.e., several

minutes" with the electrical current would be necessary. Aith household

current, in which the mechanism of death is ventricular fibrillation, the

duration of contact necessary to roduce fibrillation may be measured in

seconds or tenths of seconds, deending on the amerage. This is, of

course, determined by the resistance. Thus, with 17!-V current and 1!!!

ohms of s>in resistance, 17! m) reach the body. 'n such a case, contact

for & s would be necessary to roduce ventricular fibrillation.* 'f the oint


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m) (1.7 )" and ventricular fibrillation could occur in !.1s. Aith high-

voltage electrocution, cardiac arrest is essentially instantaneous.

'n low-voltage electrocution with ventricular fibrillation, consciousness

may not be lost immediately. 'n fact, it is very common for the individual

receiving a fatal electric shoc> to not lose consciousness, but to yell out or

state that he :ust ?burned@ himself rior to collase. This is because the

brain has aroimately 1!$1& s of oygen reserve, irresective of the heart.

Thus, an individual can remain conscious for 1!$1& s after cessation of the

heart as a uming organ. 'n cases of low-voltage electrocution,

resuscitation and defibrillation may revent death. 't should be >et in

mind that ventricular fibrillation is occasionally self-reversible in that the

heart will revert to son- taneous rhythm following a short time offibrillation.

'n high-voltage electrocution, there may be irreversible electrothermal

in:ury. Ahile the heart may start again sontaneously following cardiac

arrest, resiration might not resume because of aralysis of the resiratory

center. This is robably caused by damage to the resiratory center of the

brain stem by the hyerthermic effects of the current.

The hyerthermic effects of high-voltage currents can be seen in

:udicial eecution, where third-degree burns develo at the site of contact

between the electrodes and s>in, as well as in the observationby Aerner that,following eecution, the brain temerature was as high as 6*E=.;

Fractures Caused by Electrocution

Ahen an individual contacts an electrified source having a current of &! m)

or greater, there is generali0ed muscular contraction. Ahether the current

is low- or high-volatage, these contractions can fracture bones. Tarquinio et

al. reorted bilateral scaular fractures from a ;;!-V, 6!-/0 current

Dumas and Aal>er from eosure to a 77!-V, &! /0 current.&,6

tueland et al. described a case of bilateral humeral fractures from

contact with 11! V haheen and abet bilateral fractures of the femoral

nec>s secondary to contact with a 77!-V current.%,8 9ractures of T17 and F1

vertebrae have been reorted.+ Tarquinio et al. mention that fractures

were frequently seen as comlications of electroconvulsive or ?shoc>@

theray rior to the use of muscle relaants in this theray.&

n!oluntary Mo!ements Caused by Electricity"nduced

Contraction of Muscle

=ontact with current, esecially high-voltage current, may roduce violent


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A

B

Fi#ure 16.1 () and K" 2lectrical burns of hands re,resenting ,oints of entry.

(continued).

color, often with raised borders and a central crater with yellowish or blac>

discoloration of the burn sites caused by heat. 'f the individual is wearing

shoes, and the eit site is a foot, there may be arcing eit burns. Aith

very high voltage, there can be massive destruction of tissue with loss of

e(trem- ities and ruture of organs.

'n all cases of susected electrocution, there should be an e(amination

of the alleged source of the electrical current including electrical devices the

individual was handling at the time of death. 'n low-voltage electrocutions,

eamination of the device rather than eamination of the body will often


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C

D

Fi#ure 16.1 (continued) (= and D" 2lectrical burns of feet re,resenting eit sites

of the electrical device in use. 'n high-voltage electrocution, tissue from

the victim may be adherent at the oint of contact with the source of the

current (e.g., a metal ladder".

Manner of Death

ost deaths caused by electrocution are accidental in manner. Lot infre-

quently, these can be blamed on defective tools or electrical aliances.

2lectrocutions caused by high-voltage wires occur secondary to inadvertent

contact with a high-voltage line when oerating or in contact with a device

such as a ?cherry ic>er.@ Jther causes of electrocution are touching a

downed electrical line or inadvertently ma>ing contact with a line via a

radio antenna or >ite. The authors have also seen cases of a seual naturewhere electrodes have been found in the anus or attached to the enis.


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A

B

Fi#ure 16.$ () and K" /igh-voltage electrical burns with multi,le individualand confluent burn areas (continued).

electrical device into a bathtub while an individual is ta>ing a bath. There

are usually no electrical burns in such a case and, if the electrical device is

removed, the cause of death will be missed.

Kathtub electrocutions, both homicidal and accidental, are becomingless common, because of the fairly widesread use of low-voltage Iround-

9ault =urrent 'nterruters (I9='". These are required in >itchens,

bathrooms and outside outlets. This device monitors the current flow. 'f

there is a greater than &-m) difference, the circuit is bro>en, thus

reventing electrocution. ) normal circuit brea>er does not function until a

1&-) difference is detected. Thus, in most cases of electrocution, the

house fuse is unaffected by the electrocution. 2lectrocution in water could

also be caused by defective lights in a swimming ool. I9='s revent this

tye of accident.


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C

D

Fi#ure 16.$ (continued) (=" /igh-voltage electrical burns with multi,le individ-

ual and confluent burn areas (D" Kurn from high-voltage current conducted into

body by a metal ,late.

imately &G of lightning flashes however are ositive discharges These are


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would be a lightning boltMs hitting a crane, with the electricityMs flowing

down the metal structure and stri>ing a grounded wor>er who is

touching the crane. The in:uries roduced would be the same as if the

crane had hit a high-ower electrical line, that is, burns at the entrance and

eit sites, often multile and severe.

'n a side-flash stri>e, the bolt of lightning hits an ob:ect, such as a tree,

and then ricochets, stri>ing the individual. 'n a direct stri>e or a side-flash

stri>e where the individual is relatively close to the ob:ect from which the bolt

:ums, the current can either sread over the surface of the body or enter it,

or it can follow both routes. 'n most cases seen by the forensic athologist,

the current has both flowed over the surface of the body and entered. 'n

such cases, it is quite common to find the clothing torn, shoes burst, hairseared, burns on the s>in caused by 0iers and other metal ob:ects heated

by the lightning, and burns caused by the entrance and e(it of current.

=utaneous burns are not severe but always resent.11 Jn histological

eamination, the eidermis is searated from the aillary dermis. uture

of the tymanic membrane is resent in aroimately 81G of cases.11

Jb:ects constructed of ferrous metal on thebody may be magneti0ed. Jther

metal ob:ects, such as coins, may show burns. The torn clothing and burst

shoes sometimes have led to misinterretation of the nature of the in:uries.

Heole struc> by lightning and found net to a road have been thought to behit-and-run victims. 'f one is inside a metal vehicle, such as a car or train,

when it is struc>by lightning,the robability of in:ury is etremely small. Jn

rare occasions, death or in:ury has been reorted when an individual was

using a telehone and the line was hit by lightning.17

Deaths from lightning are caused by high-voltage direct current. Death

is caused by cardioulmonary arrest or electrothermal in:uries. Aith a

direct hit by lightning, death is robably inevitable, because of burns and

in:ury to the resiratory center of the brain. )merage in this case wouldbe in the >iloamere range. 'f the electrocution is secondary to a closeoint

of imac- tion, survival may be ossible. 'n fact, most individuals in:ured

by lightning do survive. Jne of the lesions considered athognomonic for

lightning in:ury is the ?arborescent@ or fern-li>e in:ury of the s>in called

Fichtenberg figures (9igure 16.*". This lesion is a atterned area of

transient erythema that aears within 1 h of the accident and then

gradually fades within 7; h. The erythematous mar>s are not burns. Ten

Duis et al. believe that this lesion is caused by ositive discharges over the

s>in.1* They hyothesi0e that the lesion occurs when an individual struc> bya negative lightning bolt is then hit by a secondary ositive flashover from


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Fi#ure 16.& ?)rborescent@ burn of lightning.

'eferences

1. ornogyi 2 and Tedeschi =I, 'n:ury by electrical force, in Tedeschi =I, 2c>ert

AI, Tedeschi FI (2ds"3Forensic Medicine. Hhiladelhia, AK aunders =o,

1+%%, 6;&-6%6.

7. Kruner ND, /a0ards of electrical aaratus.Anesthesiology 1+6% 783 *+6-;7&.

*. 9erris FH, et al., 2ffect of electroshoc> and health. AIEE Trans 1+*6 &&3;+8.

;. Aerner )/, Death by electricity,NY MedJ 1+7* 1183;+8-&!!.

&. Tarquinio T,Aeinstein, D2 and Virgilio, A, Kilateral scaular fractures from accidental electric shoc>.

J. Trauma. 1+%+ 1+(7"3 1*7-1**.

6. Dumas NF and Aal>er L, Kilateral scaular fractures secondary to electrical shoc>.Arch. Orthopaed

Trauma !urg, 1++7 111(&"378%-8.

%. tueland DT, et al., Kilateral humeral fractures from electrically induced muscular sasm. J. o"Emerg.

Med. 1+8+ %(&"3;&%-+.

8. haheen ) and abet L), Kilateral simultaneous fracture of the femoral nec> following electrical

shoc>.In#ury. 1+8; 16(1"3 1*-1;.

+. a:am O/, et al., 9racture of vertebral bodies caused by accidental electric shoc>.J.Indian Med Assoc.

1+%6 663*&.

1!. Aright O, Krois0 /I, and human D, The investigation of electrical in:uries and deaths. Hresented at the

meeting of the )merican )cademy of 9orensic cience, eno, LV, 9ebruary 7!!!.

11. Aetli =V, Oeraunoathology3 )n analysis of ;& fatalities,Am J Forens Med

$ath 1++6 1% (7"3 8+-+8.

17. Nohnstone K, /arding DF, and /oc>ing K3 Telehone-related lightning in:ury. Med J Aust 1+86

1;;3%!6-%!+.

1*. ten Duis /N, Olasen /1, Li:sten AL, et al., uerficial lightning in:uries

P Their ?fractal@ shae and origin.%urns 1+8% 1*31;1-1;6.

electrocution 16

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