Lie detector polygraphs are used mainly for interrogating people involved in crime by the government investigating authorities. But many people, who are subjected to this test, sometimes end up with ruining their careers. Lie detector tests can never be the stand in the court of law as a reliable means of evidence. Then why every now and then people are subjected to lie detector test?

The present controversy has started with cricketer Kale. A proper interrogation is required whether he has offered the money to get his selection done, but not through a lie detector as a final confirmatory test. And why only Kale is subjected to this test, why not the selectors?.

The theory underlying a lie detector or a polygraph test, in more scientific terms, is that lying is stressful, and that this stress can be measured and recorded on a polygraph machine. Lie detectors are called polygraphs because the test consists of simultaneously monitoring several of the suspect’s physiological functions like breathing, pulse and galvanic skin response (finger tip sweat) and printing out the results on a graph paper. The printout shows exactly when, during the questioning period, the biologic responses occurred. If the period of greatest biologic reaction lines up with the key questions on the graph paper the questions that would implicate the person as being involved with the crime stress is presumed. And along with this presumption of stress comes a second presumption that the stress indicates a lie. The underlying premise of the Chinese rice technique that lying spurs physiological change remains the core theory behind the technology.

It was Dr. William Marston, a Harvard psychologist and father of lie detector technology, who postulated that lies were invariably accompanied by a spurt in blood pressure.

Supporters of lie detector tests claim that the test is reliable because very few people can control all three physiological functions at the same time, and that polygraph examiners run pre-examination tests on the suspect that enable the examiners to measure that individual’s reaction to telling a lie.

On the other hand, critics of polygraph testing argue that many subjects can indeed conceal stress even when they are aware that they are lying, and there is no reliable way to distinguish an individual’s stress generated by the test and the stress generated by a particular lie.

Blood pressure, respiration, and skin resistance are all physiological parameters and can change due to a variety of reasons other than speaking a lie. Indeed, no study exists to support a universal correlation between, say, sweaty palms and prevarication. And a polygraph cannot differentiate between anxiety caused by dishonesty and anxiety caused by other factors.

The fundamental problem with lie detectors is how operators establish what a lie looks like. Subjects are peppered with a variety of "control questions" to which the examiner anticipates a dishonest answer. Those who insist, for example, that they never stole something as a child or never tried illegal drugs in their youth are assumed to be lying and the examiner then uses those responses as a baseline for detecting deceptive answers to other questions. Polygraphs not only falsely accuse honest people of lying they also fail to detect skilled liars.

But the public’s innate trust in the reliability of the equipment, reinforced through countless cop dramas, makes the lie detector an indispensable tool for extracting confessions. If people believe they can’t fool the machine, the theory goes, they’ll confess before they’re actually trapped in a lie. Over 90 per cent of the information it obtains during security screenings comes from confessions prompted by lie detector tests.

Polygraph tests are nothing more than a part of the interrogations. The test is operator dependent and is biased against the truthful. Polygraph testing can and has been easily defeated through counter-measures.

The US courts in most jurisdictions doubt the reliability of lie detector tests and refuse to admit the results into evidence. Some states do admit the results of polygraph tests at trial if the prosecution and defendant agree prior to the test that its results will be admissible.

The polygraph on the other hand is a very useful tool in the hands of doctors. They use it as bio feedback techniques in managing stress. The stress parameters are shown as red light and the relaxing parameters as the green light. The person can train himself to convert the red into green parameter state.

Stress is the body reaction of the interpretation of a situation. But the body reaction can be changed by learning yoga and meditation. Therefore, people who meditate will be difficult to be interrogated using the polygraph.