Electrocution

RK Wright MD JD FAAFSrkwrightmd@gmail.comwww.rkwrightmd.com

My Interest in Electrocution dates from 1972

1. I was the deputy chief medical examiner for the State of Vermont

2. I got a call of a death near an abandoned farm house. It was abandoned before WWII

3. As the price of copper had reached astronomical prices the young man was stealing copper.

1. Unbeknownst to the young man, the copper wire to the abandoned farm house still was energized 4,000 v line to ground.

2. He was grounded through his thighs through the driven ground on the pole.

3. He died an asphyxial death4. I had been tought that one fibrillated

My Interest in Electrocution dates from 1972

1. He asphyxiated because the current through his body, although it went through his heart, right hand to thigh, was above the fibrillatory threshold.

2. I=V/R Amps=Volts/Ohms3. In his case 14.29 amps (4000/280 ohms)4. Ventricular threshold is ~100 mamps – 1

amp

My Interest in Electrocution dates from 1972

So I have spent 35 years

� Primarily interested in Electrical Deaths and Injuries

� I have successfully gotten an attorney acquitted of murder in Nagpur, Mahashtra, India

Electrocution

1. Death or injury caused by the flow of electrons through a person’s body

2. Historically, defined as death from the flow of electrons through a person

Used by United States

to Kill ConvictsDrawing showing the electric chair in use in New York State of Mr. Kemmeler who was the first person to die of intentionally applied electric current.

ElectrocutionKilling people on purpose came to be part of the War of the Currents.Thomas Edison had installed a DIRECT CURRENT (DC) Generation plant in New York City.Nikola Tesla had perfected ALTERNATING CURRENT (AC)

War of the Currents

Thomas A Edison

George W Westinghouse

War of the Currents

Nicolas Tesla

War of the Currents

Edison, who had invested a great deal of money into DC, pushed the electric chair as a demonstration of the dangers of AC. As Westinghouse knew what Edison was trying to do, he would not sell any of his equipment to the State of New York.Edison had his agents buy Westinghouse equipment and then sold it to the State of New York.

War of the Currents

Killing people certainly made the point that AC is dangerous, however Westinghouse won the war by inventing the ELECTRIC METER. Edison sold subscriptions to electricity , allyou could use one price.Westinghouse sold metered electricity, depending upon how much current is used, you paid per kilowatt hour.

War of the Currents

War of the Currents

AC won the war

War of the Currents

1. The single greatest advantage to AC is that through the use of transformers, the voltage can be increased to 500 kV and even 700 kV to transmit huge amounts of power over long distances with small wires and then set the voltage down for industrial and residential use.

2. DC cannot have its voltage changed

AV vs DCAC is generated at a few kilovolts, transformed to 100’s of kilovolts.Transmitted long distances using small wiresDistributed at lower voltagesusually 4,800, although this varies from 2,000 to 13,000.And then finally stepped down to 240/120 for the residential user or 480 for most industrial use.

ACThe final step-down transformer takes 4800 volts and converts it to two legs.Each leg has 120 v leg to ground and 480 leg to leg.Almost, but not all electrocutions at low voltage are leg to ground or 120 v

Typical Circuit Breaker Box

Black, gray, red are 120 v line to groundBare wires on left are groundWhite wires are neutralFor 120 v electrical appliance to work, it requires a hot wire and a neutral.For a 240 v it takes a double breaker across both legs of the 240 v

No LET GODuring WWII, the army was having a large number of deaths from electrocution.In an effort to reduce these deaths they contracted with Professor Dalziel to determine the no let-go threshold for men women children and babies.He remarked that he could not find the threshold for babies, as all the did was cry.

No Let GoLess than 0.001 amps (1 milliamp) cannot be felt.10-17 milliamps no let-goThe hand cannot open voluntarily due to the effects of the current.Professor Dalziel reported no deaths.The photo on right was taken by Professor Dalziel while one of his volunteers is trying to open his hand

Ventricular Fibrillation

At 70 milliamps to 1 amp, the heart will try to follow the alternating current as the pacemaker. In the Americas alternating current goes from positive to negative 60 times a second or 3600 times per minute.(Note how close Dalziel was to the fibrillatory threshold)Dalziel used AC, he tried DC, but could only get people to do the experiment once. DC hurts a lot more than ACDalziel used hand to hand, which crosses the heart.

Ventricular Fibrillation

No pulseNo blood pressure after a few secondsNo brain activity after ~15 sec

How long do people feel

pain after v-fibWWII gave us the answer also.A device was constructed to blow up a cuff around the neck to 300 mm of Hg. This cut off all the circulation to the brain. The average time to unconsciousness was 7.8 seconds.As V-Fib results in cessation of blood pressure after around 7 seconds, you can see why persons who are shocked go ~15 seconds after being shocked.We won the war. No one was charged with war crimes

Effects of electricity ~15 mamps to many amps

� Lower extremities1. Foot extends2. Ankle extends3. Knee extends4. Hip extends5. Back extends

� Upper Extremity1. Fingers and thumb

flex2. Wrist pronates3. Elbow flexes4. Shoulder flexes

Man being Tasered

Note hyperextension of back, hips, knee and ankle

If not supported he would have fallen on his back

� Lower Extremity1. Falls over

backwards

� Upper Extremity1. Grasps energized

or grounded object and pulls it under chin

Effects of electricity ~15 mamps to many amps

Down Power Line

When a power line is down it charges the ground so that a differential voltage exists in the ground,If a person is barefoot or has conductive foot wear, then the person, on the basis of lower extremity electrical extension will fall onto their back, even if they are not touching the downed wire.

Downed Distribution

wireTypical effects on the ground of a downed wire

Electric wires are almost all ACSR type

� ACSR wires are the predominant wires used in the USA (except old wiring around Vermont, Ohio and Illinois)

� Aluminum Clad Steel Reinforced� They are bare wires insulated by air.� The amount of air required for insullation

varies with the voltage

A cell at rest has a resting

potentialIt is 70 to 100 millivoltsWhen electrons flow outside the cell, it depolarizesThis causes the cell to do whatever it does.

Electricity Effect

When a cell is depolarized it does what it doesMuscle cells contract about 200 milliseconds after being depolarizedNerve cells also send a signal, generally sooner than 200 milliseconds

Rigor MortisWill occur nearly instantaneously after the passage of 50 milliamps and higher amounts of current

Molecular View of Muscle

Contraction1. In contraction troponin and

CPK are released into the blood stream

2. Normal values for both are for sedentary individuals

3. Active workers (construction laborers) usually have much higher values for “normal”

Electrocution

1. With alternating current there is no entrance or exit

2. Entrance and exit changes 60 times per second.

3. Thus in investigating a possible electrcution one needs to find the energized side and the ground side

Electrocution

Thank you for your attention