I developed this as a way of making Physics more interesting, and trying to bring in a few ethical issues.  I gave it an age limit - Year 10 or above.  Most liked the gore and the guts, but went a bit quiet when they really thought about it.  I've pasted the main points of the talk on this site. All comments welcome -  e- mail me.
 
 

Introduction:

Ancient law: ‘an eye for an eye’ - life for a life;
 but then we end up with more murderers
 BUT condoned by law.

Death penalty allows for legalised killing.  This may be by the victims’ family (eg stoning in Middle East) or by state executioners.

 A few years ago I saw a job ad in Uganda: wanted hangman; O/Level Physics useful

In US the executioners have a ‘get out clause’: firing squad where blanks are fired; three computer controlled switches for lethal injection (only one works) etc.
 

 Methods:

Currently 97 countries use the death penalty, but the number of countries which execute people is smaller.

In 1994 Amnesty International knew of
 2 331 prisoners being executed
 4 032 prisoners sentenced to death

 87% of executions happened in three countries:
   China
   Iran
   Nigeria
 Hundreds of executions were reported from Iraq but not confirmed

 USA has the highest record of executions of juvenile offenders (under the age of 18):
  6 since 1990

 Worldwide, the method most used is shooting, followed by hanging.

 Three methods in particular are relevant to this talk:

These methods have developed over time - centuries - to become, supposedly, more humane.
 

 Beheading

Using an axe or a sword generally did not work as it took several attempts to kill the criminal.  This was partly due to blunt instruments and drunken executioners.

In 1792 the Guillotine (named after Dr Joseph Guillotin) was invented.

 Advantages:
 

•  the blade fell down a column so you knew where it would land
•  the victim was held in place so could not escape
•  many victims could be dealt with quickly (important in the French Revolution)
•  it could be arranged easily for a public spectacle
•  it was reliable - usually worked first time

The last French execution by guillotine took place in 1977 and capital punishment was abolished there in 1981.

Cause of death:

After the blade falls there still is some oxygen in the brain so the prisoner is actually conscious for a few seconds (up to 7). There are stories of heads blinking......

Death from shock and anoxia follows.  Even so, it is probably one of the least cruel methods used.
 
 

 Hanging

Remember hanging is the second most widely used form of execution in the world today. It was probably first used in Persia 2500 years ago. In UK it was abolished in 1964.

In the early days, prisoners were hung from trees (standing on carts which then pulled away). then gallows were developed; the most famous was at Tyburn in London (near Marble Arch now). Until 1900 hangings were public events.

In 1885 a ‘proper’ gallows was designed for use throughout the UK.  It could hang up to three prisoners side by side.  The drop height (crucial to the method of death) could be adjusted carefully using chains.  A single lever pulled the trap door away.  The noose in the UK usually did not involve many coils (like you see in cowboy films) because these tended to strangle rather than break the neck.
Usually a single knot was used, with the free end of the rope passing through a brass eyelet so it could move more freely.  The rope (made from hemp, and 2cm diameter) was a little over 4 metres long and was prestetched - usually done the night before by hanging a sandbag of the same weight as the victim from it. The noose part of the rope usually had a piece of chamois leather wrapped around it - so the skin would not break. Hemp was the best as it was soft and strong ! Modern materials eg nylon were too elastic (too much energy was used stretching them rather than breaking the neck).

In America ropes were boiled rather than prestretched. They were then waxed or greased to help the knot slide.

Drop methods:

Short - only a few tens of cm; death by strangulation followed, after about 15 minutes. During this time the victim was conscious. Lucky ones died due to pressure on the vagal nerve. Sometimes, after half an hour, a victim was cut down, to live on.

Long - usually over 1.5m; death usually was quick due to a broken neck from a sharp jerk as the body fell. At the end of the drop the body is still accelerating but as the head is held the noose delivers a massive blow which breaks the neck.  If the drop height is too much, then the head does get ripped from the body.  There are formulae used, depending on the weight of the prisoner and the positioning of the eyelet of the noose.................
Death is from comatose asphyxia; this means suffocation. The heart may actually beat for 20minutes or so, but  the person is unconscious due to fracture or dislocation of the spinal cord.

Hanging in the UK has been abolished for murder BUT technically still could be used for High Treason, piracy and arson in a naval dock yard.
 
 

 Electrocution

A current of 0.2A at 230V at mains frequency 50Hz can kill. This is less than the current in a light bulb.  There are many variables that will determine if you die:

•   the resistance of your skin - sweatiness
•   the frequency of the ac source (with dc - no hope)
•   how you touch the source of electricity - muscle contraction
•   the condition of your heart and nerves - electrical pathways in your body

History of the Chair

Edison (invented the light bulb) thought dc electricity was ‘best’ and should be used throughout America.

Westinghouse made ac generators which could send electricity further and at a higher voltage.

Edison heard about accidents from high voltage ac so said Westinghouse was wrong - his electricity was lethal.
 There was a commercial battle. However the US authorities got involved as they were after a safe, reliable way to kill people (a new means of execution).

Lots of animals died as they tested the ideas; both Westinghouse and Edison were horrified. Edison made sure that all  experiments he did used Westinghouse’s generators, just to give them a bad name.

The first electrocution took place in August 1890. It took a couple of tries before the victim, wife murderer Thomas Kemmler died.

Many executions are ‘botched’ with reports of smoke and even flames from the victim’s body.  The physiology is grim:

•   inner body temperature goes up to 59 degrees C
•   outer body too hot to touch
•   hair can burn
•   eyeballs pop out (hence the mask)
•   urine boils
•   blood pressure can increase so violently that blood vessels explode and blood shoots out of the body

• The voltage is usually 2000V or more; current 5A
• A simple calculation shows the power is 10 000W
• Each burst - usually two - lasts 1 minute.
• The total energy into the body is 1.2MJ; that’s as much energy as a burning Bunsen flame for 1/2 hour.

The head is shaved an the cap has a natural sponge soaked in salt water stuck in it. One time they used an acrylic sponge - it melted and caught fire.

The bottom electrode is attached to a shaved leg. In early designs the second electrode was at the base of the spine.

Electrocution is the modern day equivalent of burning someone at the stake; this time the stake is inside.  No one knows the pain involved; the cause of death is asphyxiation, but before this happens the prisoner is fully conscious, but paralysed.

All executions in the US must be witnessed. One regular witness said: ‘The only way you can deal with it is by being very familiar with the crime and keeping the victims, and what was done to them, in mind.’

So, what about that ancient law ?

As Gandhi said: ‘An eye for an eye, and we’d all be blind’.

Karin Parker August 98