Authored by Geoff Vaughan in Criminal Law
Published on 09-25-2009
A polygraph instrument cannot detect actual lies, but rather measures bodily changes that may indicate that a person is trying to be deceptive when giving answers to questions. This device has several medical components which monitor a person’s respiratory rate, blood pressure, heart rate, and electro-dermal activity. Any fluctuations from a person’s normal measured levels could show that that person is not being truthful. The examiner must be properly trained to connect the Polygraph to the interviewee and interpret the test results. When people are trying to deceive someone, they usually become stressed. This stress causes involuntary internal and external responses that the polygraph instrument can detect.
Although most often polygraph exams are given during criminal investigations, some government and private businesses will require people to take a polygraph before they can be hired. These tests are usually given for positions where someone’s background information is critical for the security of the organization. For example, if someone will work around sensitive information or highly valuable merchandise, the employer will want to know that the individual does not have a criminal history.
The polygraph test is not 100 percent reliable, and can be beat. Several businesses exist specifically to teach people how to avoid getting the examiner to determine that you are being deceptive in your responses. The three possible results that can be determined are deceptive, truthful, or inconclusive, and most people who follow a few suggested steps can at least reach inconclusive results.
Before even meeting with you, the examiner will plan and write out specific questions. This person will hook you up to the polygraph instrument with several sensors. The examiner will read you a series of questions that often involve “yes” or “no” answers. Some of these questions are control questions, which are used to measure baseline responses, and the other questions are considered to be relevant questions. The entire exam usually takes an hour, but can take longer.
The best way to throw off the test results is to learn techniques that will change your heart rate and blood pressure. The goal is to not have a very big deviation in your physiological reactions between control and relevant questions. One technique is to control your breathing. When you are asked control questions, try to breathe slower or faster. You will then have to breathe normally again for the next question. Another tip is to think of something really scary or exciting during the control questions, which can speed up your pulse. Some people prefer to use the technique of causing themselves pain during the control questions. Other people have success at beating a polygraph test by squeezing their sphincter muscle during these questions. You can also put a tack in your shoe and step on it during control questions, or bite your tongue. You need to make sure that the examiner does not notice that you are doing these things. Some examiners will make you take off your shoes because the foot trick is so popular. Others have specific seats that can sense if you squeeze your buttocks. Examiners have learned to look for ways people try to beat the tests, so you have to be very cautious when using these tips.
Remember that no one can tell if you are telling the truth except for you. If you practice breathing and psychological techniques to make your heart race during control questions or cause yourself pain, you can beat the test. The key is to control your bodily responses throughout the polygraph exam.