Lie Detectors
One of the most famous pieces of forensic equipment, the polygraph or lie detector, is also one
of the least reliable. It cannot detect whether someone is lying or not; it can only tell us whether the
person being tested is agitated or not. It gives us information about the physiological and psychological
condition of the person, but it cannot tell us why the person is in that state. For example, a shy person
may react adversely to the machine, when a more outgoing may not. Similarly, a sick may perform
badly, although he may have done better had he been well.
A more recent innovation in the search for the truth in the spoken word is the voice analyzer.
Unlike the polygraph, the person tested does not have to be attached physically to the machine. It is
said that sub-audible tremors during speech can be detected by the instrument; these tremors being,
apparently, characteristic of people who are lying. Several similar devices are being marketed in the
USA, but I view these developments with deep suspicion.
Finally, I must mention a story told me by Dr William Aulsebrook of South Africa. Apparently, the
Zulu people have a fail-safe method of identifying a liar. The suspects are brought before a judge and
each is fed a spoonful of flour, and then asked to speak. Only the guilty man will have a dry mouth and
the flour will fly about as he speaks, revealing his guilt. I cannot say that the system is in any way
inferior to the polygraph; the reasoning is the same, but the conclusions are unreliable.
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