How to Beat a Polygraph

A Polygraph is an instrument used to detect lies. The subject is asked a number of questions. Physiological changes like changes in blood pressure, pulse and respiration and skin conductivity when questions are being answered, are measured and recorded. The polygraph is not a foolproof means of testing for lies. Here is how you can beat a polygraph.

Prepare before hand for the polygraph test. Find out as much as you can about the polygraph. However, it is also important to behave as if you do not know much about it. If you show-off your knowledge, then the polygrapher may assume that you are concealing some vital information. Before going for a polygraphy, think about all the questions that the examiner is likely to ask. You must approach the interrogation seriously. The style of dressing should be appropriate. Do not act nervous. Bear in mind that not only what you say, but also how you behave before or at the time of testing up until you go out of the testing room, is recorded.

The questions that the polygrapher has in mind are of three types: relevant, irrelevant and control. Irrelevant questions are those that the polygrapher asks routinely like, 'where do you live' or 'what is your name'. Questions like 'what is your favorite food' also come under the category. Such questions do not have direct bearing on the case or are already known. On the other hand, relevant questions are very crucial and of consequence. Control type of questions may not have direct relevance but could still make you uneasy. For e.g. 'Have you ever lied to your partner or in your work place'? Control questions are ones that could make almost anyone uneasy.

At the outset, polygrapher will explain the basics of polygraphs and put you to ease. He will read out the questions that he intends to ask you. Therefore, you can prepare yourself mentally as to how to tackle these questions. These questions have to be answered only with 'yes' or 'no'. You do not have to give explanations.

It is crucial for you not to admit anything relevant. The polygrapher may try to trick you to make confessions by convincing you that he has detected some abnormal reading to your answer to a certain relevant question. So stick to your answer, no matter what.

There are ways to affect the machine readings. You have to learn to control your blood pressure and heartbeat. The normal breathing rate for all the answers except to control questions should be 15-30/minute. For the control questions, you could make it faster. Physiological stress should be seem discernibly more while answering control questions, so that the polygrapher will feel that you had lied in answering that question, but have been truthful about relevant questions. By biting your tongue of contracting your anal sphincter muscles, or imagining some thing frightening, exciting, or happy, you can help you influence your physiological response to questions. You can throw the machine off track, thus.

The polygraphy has many limitations. If you can help it, avoid one. In the U.S, if it is proposed as part of a criminal investigation, you can refuse to take it. In most countries, the polygraphic evidence is not admissible in court.