Experts will say that polygraph tests or lie detector tests are almost always accurate, giving its results a high ranking in reliability. Others, after research and study will not agree. Some claim that it has a 7 out of 10 chance of being right, while experts claim that is will be a reliable result. This brings us to the question: how accurate is a lie detector test?

The results a lie detector gives out are accurate sometimes, but not foolproof.

1. How does it work?

The machine assesses three main things, blood pressure and heart rate, respiration and skin conductivity. Since most of the people that take the test are already nervous, their heart rate is soaring before the machine is even turned on. This makes it hard for the device to ensure whether the person is lying or just plain nervous.The initial starting of the polygraph test is simple, a series of questions is asked, before the actual interrogation, where the subject is induced with nervousness about failing the test.

That way should they lie during the test, it will become apparent in their heart rate monitors and the sensors on their fingertips.

2. What to ask:

There are several different types of questioning techniques used in the polygraph test; some are easy while other, more direct ones are to test if the subject can lie easily.

Staring with easy questions, such as asking the subject’s name, age and physical details will give the machine and the interrogator an idea of how the heart rate is when the subject is not lying. When more fear inducing questions are asked, the subject will have a hard time lying. The blood pressure and heart rate will increase and the machine will detect it, assume the subject is lying.

Again, this is not a foolproof test.

3. Is it infallible?

There are ways to fool the machine even though it is a well made detection device.

People who have to take the test are often told a few days in advance, if they are not prisoners or criminals. In this time, they can gain knowledge and find out how to ‘trick’ the machine.

Since it requires a truth to be measured against the lie, many subjects study on how to keep from telling the truth. Lie detectors can be fooled easily when they deliberately keep their heart rate lowered or increased because all it does it measure. A hundred percent accurate result is not possible even though a vast majority of people do get caught lying when taking this test.

When this machine is used, it has to measure the rising of the blood pressure. It cannot detect ‘lies’ per se, why the blood pressure is rising, what caused it, that is up to the person taking the test and the one conducting it. Our heart rate increases for many reasons the lie detector device merely reports the changes, nothing else. Its accuracy is a question of the scenarios in which they were used.