016. Murder by electricity

This time I am going to tell you about a very unusual case of homicide. This is a British case. A young woman was found dead in her bath, slumped forwards in a kneeling position with one breast resting against a chrome tap. The left arm was trailing over the edge of the bath, in which was the usual level of water plus an electric fan heater immersed near the feet. The heater was connected by a long cable to a 240 volt socket in an adjacent bedroom. To all intents and purposes it appeared that the woman, while taking her bath had accidentally slipped in the bath and drowned. This is not a very unusual mode mode of death. Several people have accidentally died in this way. As regards the heater in the water, it was assumed that when the woman must be struggling to find her way out, her legs may have got entangled in the cable wire somehow and she must have accidentally dragged the heater in the bath. Since Britain is a cold country many people keep heaters in their bathroom while taking bath, so the presence of a heater in the bathroom did not arouse much suspicion. The post mortem examination seemed merely a routine formality.

However while conducting the post mortem examination, the autopsy surgeon noted two curious marks on the body. The first was on the left breast and the other was over the inside of her left arm near the axilla. These were the marks produced by electricity. This indicated that this could be a case of homicide. Subsequent investigations revealed that it was indeed a case of homicide and the husband was involved in that ghastly murder. So just two insignificant looking marks took the perpetrator of crime to the gallows. To understand about these marks let us understand about some of the basics of electricity first.

But before going on further, let me tell you that homicide by electrocution is by no means unknown. In a Hindi film of early 1970s, Gehri Chaal (An Amitabh Bachchan, Jeetendra and Hema Malini starrer), Amitabh Bachchan tries to kill the CBI inspector Jeetendra by cleverly setting up wires in his bathroom in such a way that the moment Jeetendra touches the tap, he get electrocuted. Of course by a quirk of fate he does not die, but gets away by getting simply a strong current!

Coming to the basics of electricity now. One of the important things to understand is the meaning of "current". All of us use this term daily. The word "current" signifies the quantity of electricity flowing through a wire. It is measured in units called "Amperes". We must not get worried about this term. This is a technical term and I am introducing it only for information purposes. The only thing that must be understood here is that a current of, say, 2 amperes is greater than a current of 1 ampere. 1 ampere is in fact a huge amount of current. This much current is not encountered in daily life, so scientists usually talk of a lesser quantity known as milliamperes. One ampere is equal to 1000 milliamperes. To get some idea of how much a milliampere is, one must know that in an ordinary household electric bulb of 100 watts running on 250 volts, a current of about 400 mA(milliamperes) flows. When a current is flowing through a wire, what is actually flowing through the wire are tiny ball like structures known as electrons. These balls are too tiny to be seen with the naked eye or even with the strongest microscopes. More the number of electrons flowing through the wire, stronger the current. How tiny these electrons are, can be estimated from the fact that 6. 25 quadrillion electrons (this number can be written by writing 625 and then adding 13 zeros after it!)must pass through a wire or through the body every second to set up a current of just 1 milliampere. Most people can voluntarily tolerate a current of up to 30 mA applied to the hand, which results in painful muscle contractions. When the amount of current is increased to 40mA, consciousness is lost. At 50mA the heart loses its rhythm and starts beating very fast-even upto 600 times a minute(the normal rate is only 72 per minute). This phenomenon is known as ventricular fibrillation. Death occurs when the current is increased to 80mA.

The time for which the current passes through the body is also important. If a small amount of current passes through the body for a longer period, the net damage to the body may be more than when a large current passes through the body for a much smaller period. Thus it is wrong to believe that a large current is necessarily fatal. One can escape the ill-effects of a large current if the exposure to the current is for a very small period.

Another thing to understand is the significance of "voltage". Voltage is like the "pressure" of electricity. This pressure is measured in units called volts. Just as more water pressure causes more water to come in our water taps, more electrical pressure( i. e. greater voltage) causes more electricity to flow through the wire. If this same voltage is applied to the body, electricity starts passing through the body causing harmful effects. The domestic supply in India is 240 volts, which is quite fatal. That is why in several parts of USA and Europe, the domestic electricity is supplied at only 110 volts. The commonly used car battery supplies a voltage of only 24 volts, which is quite safe, but as we have already seen, even this voltage may prove fatal if the voltage is applied to the body for much longer periods. In fact cases of death have occurred when a person was pinned beneath an electrical vehicle for several hours. It is interesting to note that an ordinary torch cell supplies only about 1. 5 volts. Thus if about 160 such cells were joined end-to-end, they would supply an electric voltage of 160x0. 5 volts or about 240 volts. Thus such a combination could cleverly be used by a cunning criminal to commit murder!

When a person receives an electrical current, what actually happens is that an electrical current passes through his body. It enters the body through a particular point, known as the entry point and exits the body through another point, known as the exit point. What is important to understand is that the current leaves characteristic burn marks, both at the entry and the exit points. These are known as `electrical marks' or `electrical burns' or `Joule burns'. The term `Joule burns' comes from the name of an English scientist James Prescott Joule (1818-1889), who was the first scientist to work out the formula governing the development of heat by an electric current. According to this formula if the current flowing through the body is doubled, the heat generated is not just doubled, but is increased 4 times! Similarly if the current is increased three-fold, the heat increases 9 times. In other words, the heat increases as the square of the applied current. This is indeed a dangerous situation.

The temperature of the skin under the live wire may reach as high as 95^oC. Such a high temperature splits the layers of the skin and produces a raised blister. When the current ceases, the blister cools and collapses, giving rise to a characteristic mark which we have already talked about. A characteristic feature of this mark is that the edges of this mark are quite blanched. This mark immediately tells the crime scientist that the deceased may have been electrocuted. This is the mark that I saw on the body of the woman and which I showed to my colleague.

To get back to our case now. After the suggestion of the autopsy surgeon, the police called the expert electricians and asked them to examine the concerned heater. Surprisingly it was found that the third `earth' wire was disconnected from the earth pin inside the plug. This clearly established the intentions of the murderer who incidentally turned out to be the woman's husband himself. Since the enamel lining of the bath can not allow the current to pass through, the earthing of the current could only occur through the bath water via the chrome waste pipe. The woman was subsequently pushed against the tap by her husband in such a way that her left breast touched the metal tap. This started another path for the current to pass out-through the body and then through the metal tap. This path presumably took the woman's life.

The husband was subsequently questioned by the police regarding this. Initially he kept denying everything, but when he was presented with the forensic evidence, he broke down and confessed to everything. This was a remarkable victory for forensic science. This case also illustrates, how fertile human mind can be, especially when it comes to crime.

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