Conduit

Deaths caused by electrocution are infrequent and these are accidents, with suicides rare and homicides even rarer. These deaths involve both low voltage (<600 V) and high-voltage (>600–750 V) currents. They virtually always involve alternating currents. Humans are four to six times as sensitive to alternating currents as to direct. Alternating currents between 39 and 150 cycles per s have the greatest lethality.

Amperage, or the amount of current flow, is the most important factor in electrocution. It 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 expressed in the formula:

A = V/R

For electrocution from low-voltage (110–120 V) household current, there must be direct contact with the electrical circuit, with death primarily caused by ventricular fibrillation. In high-voltage accidents, direct contact with the wire is not necessary. As the body approaches the high voltage line, an electric current (arc) may jump from the line to the body. Death from high-voltage electrocution is usually caused by either the electro thermal injury produced by the current, or respiratory arrest. The temperature generated by an arc current can be as high as 40,000ºC.

Resistance to electrocution in humans involves the skin. With 120 V, dry skin may have a resistance of 100,000 ohms; dry and calloused skin up to a million ohms; moist skin 1,000 ohms or less, and moist, thin skin as low as 100 ohms. With high-voltage currents, skin condition plays no significant role in resistance to electrocution.

Amperage is the most important factor in electrocution. Since voltage is usually constant, the main factor in determining the amount of amperage that enters the body is the resistance, as expressed in ohms. The minimal amount of amperage perceptible to a human as a tingle is 1 mA (0.001 A). A current of 5 mA will produce tremors of the musculature while 15–17 mA will cause contracture of the muscles, which prevents release of the electrical source. This latter current is the “no-let-go” threshold. At 50 mA, there is contracture of all muscles, respiratory paralysis and death if the current is sustained. Ventricular fibrillation occurs at currents between 75 and 100 mA. Extremely high currents, ~1 A and higher, do not cause ventricular fibrillation, but rather ventricular arrest. If the current is then turned off, and there is no significant electro thermal injury to the heart, the heart should begin to beat normally. When electrical current enters the body, it runs from the point of contact to the point of grounding, following the shortest path. Most commonly, the path is from hand to foot or hand to hand. The time necessary for a current to cause death depends on the amperage. Thus, in very low-amperage electrocutions, where death is caused by paralysis of the muscles with secondary asphyxia, prolonged contact, (i.e., several minutes) with the electrical current would be necessary. With household current, in which the mechanism of death is ventricular fibrillation, the duration of contact necessary to produce fibrillation may be measured in seconds or tenths of seconds, depending on the amperage. This is determined by the resistance. Thus, with 120-V current and 1000 ohms of skin resistance, 120 mA reach the body. In such a case, contact for 5 s would be necessary to produce ventricular fibrillation.

In low-voltage electrocution with ventricular fibrillation, consciousness may not be lost immediately. In fact, it is very common for the individual receiving a fatal electric shock to not lose consciousness, but to yell out or state that he just “burned” himself prior to collapse. This is because the brain has approximately 10–15 s of oxygen reserve, irrespective of the heart. Thus, an individual can remain conscious for 10–15 s after cessation of the heart as a pumping organ. In cases of low-voltage electrocution, resuscitation and defibrillation may prevent death. It should be kept in mind that ventricular fibrillation is occasionally self-reversible in that the heart will revert to spontaneous rhythm following a short time of fibrillation. In high-voltage electrocution, there may be irreversible electro thermal injury. While the heart may start again spontaneously following cardiac arrest, respiration might not resume because of paralysis of the respiratory center. This is probably caused by damage to the respiratory center of the brain stem by the hyperthermic effects of the current. The hyperthermic effects of high-voltage currents can be seen in judicial execution, where third-degree burns develop at the site of contact between the electrodes and skin, the brain temperature was as high as 63°C.

Contact with current, especially high-voltage current, may produce violent muscle contractions and these can cause fractures such as follows:

1. The back and neck arch backward.

2. The arms rotate inward the elbows flex and the hands form fists.

3. The hips and knees lock straight and the feet extend

4. If the individuals are grasping something, they will continue to do so.

Electrocution can produce accelerated onset of rigor mortis caused by the muscle contractions and depletion of ATP. If this does occur, it may be eccentric, reflecting the passage of the current through the body.

High-voltage burns may be extremely severe, with charring of the body. If the burns occur from contact or proximity to a high-voltage line, the multiple small burns are caused by arcing of the current.

In all cases of suspected electrocution, there should be an examination of the alleged source of the electrical current including electrical devices the individual was handling at the time of death. In low-voltage electrocutions, examination of the device rather than examination of the body will often provide the cause of death, because burns may not be present.

Most deaths caused by electrocution are accidental in manner. Not infrequently, these can be blamed on defective tools or electrical appliances. Electrocutions caused by high-voltage wires occur secondary to inadvertent contact with a high-voltage line when operating or in contact with a device such as a “cherry picker.” Other causes of electrocution are touching a downed electrical line or inadvertently making contact with a line via a radio antenna or kite. There have also be seen cases of a sexual nature where electrodes have been found in the anus or attached to the penis. Suicides are rare, although occasionally, individuals will build elaborate devices to electrocute themselves. Homicides are even rarer. The most common method of homicide with electrical current is to drop a plugged-in electrical device into a bathtub while an individual is taking a bath.

A lightning bolt is produced when the charged undersurface of a thundercloud sends its electrical charge to the ground. Since the undersurface is usually negatively charged, virtually all discharges are also negative. Deaths from lightning are caused by high-voltage direct current. Death is caused by cardiopulmonary arrest or electrothermal injuries. With a direct hit by lightning, death is probably inevitable, because of burns and injury to the respiratory center of the brain. Amperage in this case would be in the kiloampere range.

If the electrocution is secondary to a close point of impaction, survival may be possible. The body works and behaves as a conduit.  In fact, most individuals injured by lightning do survive. One of the lesions considered pathognomonic for lightning injury is the “arborescent” or fern-like injury of the skin called Lichtenberg figures.

Acknowledgements:

The Police Department; 

https://www.politie.nl/mijnbuurt/politiebureaus/05/burgwallen.html and a Chief Inspector – Mr. Erik Akerboom                                 ©

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