Friday, 22 August 2014


What is the real truth about lie detector testing?

The Polygraph was invented in 1921 by a medical student, John Larson, at the University of California at Berkeley and a police officer at the Berkeley Police Department, and proponents of the system, according to others, have been living a lie ever since. So what is the truth about lies and how to detect them?

Well, the Encyclopaedia Britannica, commonly regarded as the world’s most authoritative reference work, put the polygraph on its 2003 list of the world’s greatest inventions. But unfortunately for Britannica, Britannica itself has been judged by a panel of encyclopedia experts to be only 87% accurate and not top of the list. So has Britannica, through its authoritative ineptitude, helped a lie to live on?

The Polygraph, or lie detector, measures while answering serious questions, the blood pressure, pulse, respiration and skin conductivity, or the amount of electricity in the skin. Skin electricity must be the stuff that goes bang when you step out of a car and close the door. This must mean that John Larson also unwittingly invented a cure for bodily static electricity. If you don’t tell lies before you get out of the car you won’t get a shock.

Lately, the lie detector has been back in the news again on the Jeremy Kyle Show. That’s the TV show where unfaithful spouses and their accusers can shout the house down and rush off the stage and out into the street as though afflicted by mad cow disease. Whenever I watch this show, and fortunately I don’t have time to suffer it often, I can usually tell from the body language, 80% of the time, who is telling the truth and who is lying.

In one recent Jeremy Kyle Show I was surprised to find that a woman, who had me convinced of her honesty, was found by the lie detector to have lied. She immediately disputed the accuracy of the test. Some participants on the show decline to take the lie detector test with the result that their credibility is questioned on the assumption that they did not want to fail the test. But they may have declined because they did not trust the test to provide an honest result.

Polygraph testing is regularly used in the United States and Canada for criminal investigation and pre-employment screening. Polygraph evidence is admitted in court in only 19 of the 50 US states, and at the discretion of the judge in federal courts. In five states it is illegal for an employer to polygraph an employee suspected of wrongdoing.

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Outside North America polygraph testing is rare. However, recently an Indian woman accused of murder was convicted on the basis of a polygraph test, but that case was later thrown out by a higher court.

So why has the polygraph failed to gain acceptance? The polygraph is regarded by the scientific community as pseudo-science. In other words its reliability can not be proven by any scientific method. Proponents of the polygraph, usually police officers and prosecutors, claim that it is 80% accurate, but even that figure may be a lie. So what we may have here is liars trying to catch liars, which reminds me of something my mother told me long ago: “Don’t trust people who repeatedly tell you how honest they are.”

In 2003 the United States National Academy of Sciences issued a report on polygraph testing and concluded that proponents of the system were using research material that was flawed, unscientific, unreliable and biased.

Opponents of polygraph testing say that it is too easy for innocent people to fail the test and for skilled liars to beat the test.

But there is also another argument for banning polygraph testing which has nothing to do with its accuracy. By forcing a defendant to submit to the test may be requiring the defendant to be a witness against himself, which would be a breach of his human rights in any country that claims to be a democracy. But there are other tests, proven scientifically, which also put a defendant in that same situation; breath and blood testing for alcohol or drugs.

Of necessity, the margin between upholding rights and upholding the law to protect others needs to be just a little flexible at times, but tests that have no scientific foundation should have no place in any country’s justice system. Polygraph testing is nothing more than twentieth century witchcraft with wires.