Leonarde Keeler invented something to detect liars. The device is so called “Polygraph”. Private detectives in the UK have gone through a wide research on this device and its usages. And it is decided that a polygraph is mostly unsuccessful in detecting a highly skilled or excessively nervous lair. Its best performance is considered to be 98% of success.
The courts, for some reasons, still don’t accept the result of the polygraph. But it is still used by many police and investigation firms.
How It Works
A lair is detected by three means (excluding his or her confession) during an investigation– his/ her breathing, heart beat and sweating. Keeler’s polygraph is a combination of all these three detective sensors or circuits.
For example, a suspect of a murder is strapped around his/her chest and arms. Then he is asked whether he has shot the victim or not. If his blood pressure and heart beat increase suddenly and if it go much high, then it is taken that he has, no matter he confesses it or not. The suspect may also sweat. The sensors set within the polygraph will provide results for all three reactions.
But unfortunately, this outcome of a polygraph, of a machine that cannot lie, is not considered as facts in courts. The outcome of a polygraph sometimes breaks the confidence of a lair; he feels caught and confesses his crime. Only this confession is accepted in courts.
In many cases lawyers prove their clients innocent despite of the fact that their clients were suspected as liars by the polygraph test. The lawyers often get advantage because the courts of the UK do not admit polygraph test as evidence.
Polygraph test is still important for the private investigators. The UK private investigators often find their necessary clues from the result of the polygraph tests. In other cases the private investigators simply understand whether to continue investigation on a certain person or not from the result of the polygraph test.
Private investigators of the UK often follow a trick which is actually given by the Leonarde Keeler. In this polygraph test a suspect will be shown ten cards. During the process the heartbeat, sweating tendency, pulse etc are measured. If an unusual change notices in the heartbeat, sweating tendency or in the pulse rate the private detectors generally find it’s important to further investigate the suspected person.
Well, there may be many arguments about the moral validity of this test but the usefulness of this test cannot be denied. There are many examples when a polygraph test has guided the private investigators towards the truth. The practical experience of those private investigators cannot be denied. So this test is very useful for almost all the private investigators of the UK.