Truth Or Lie? Should You be Honest on a Polygraph?

So, you are about to be subjected to a polygraph test because you are applying for a job involving lots of money, controlled substances or the security of others. Naturally, to get hired, you will have to pass the exam. Does this mean that it’s perfectly fine to lie while you are strapped to a lie detector machine to guarantee employment?

While it does not guarantee a no deception indicated report, truthfulness during a polygraph examination can increase one’s chances of passing the test. Especially if the lie detector exam is done to determine a person’s veracity, such as a screening process for a sensitive job, being honest is wise.

Read on if you are considering lying just to avoid failing your polygraph test.

I will tell you some of the reasons why even truthful people sometimes fail the examination. You will also come across some of the most important things you need to know about using countermeasures in order to beat the test.

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Can You Fail Lie Detector By Being Honest?

Despite being truthful, it’s possible for some innocent individuals to get a diagnosis of deception indicated. As a matter of fact, based on an experiment, nearly 17% of the subjects who failed the polygraph were innocent. But there are also instances where telling the truth may lead to an inconclusive result.

Although it’s true that being honest can increase your chances of passing a lie detection exam, there is no guarantee in the world of polygraphy — you can tell nothing but the truth and still appear deceptive.

A truthful person being reported as deceitful is called a false positive.

There are many things that can cause you to fail a polygraph examination even if you answer each and every yes or no question truthfully. Leading the list is too much anxiety. Since a lie detector test can perceive significant physiologic changes but cannot identify the cause, an anxious person who is innocent can be mistaken for being guilty.

Both anxiety and stress as a result of lying can cause the same things — elevated blood pressure, faster heart rate, rapid and shallow breaths and sweatier skin.

Certain medical conditions, too, can increase the chances of an innocent person failing a lie detector test. Someone who has hypertension, for instance, can appear as though he or she is being deceitful due to the readings a polygraph machine obtains as a result of raised blood pressure and, in most instances, accelerated heartbeat.

If you think that taking blood pressure medications is the key to passing the test, think again.

Most medications for heart-related concerns, such as hypertension, can lower blood pressure and heart rate, too. So much so that both psychological processes may not change even with the presence of a stimulus such as anxiety. As a result of this, someone who is managing hypertension with medications may end up with an inconclusive result.

A guilty person who is taking them may also get a false positive easily.

Because certain medical conditions and drugs and medications can influence the result of a lie detector test, examiners must determine the medical history of subjects during the pre-test phase.

Do Countermeasures Help You Pass a Lie Detector Test?

A polygraph test is vulnerable to countermeasures. It’s one of the few things that keep the examination from having a 100% accuracy rate. Some countermeasures work better than others. If the examiner detects the use of countermeasures, the exam can be discontinued and a purposeful non-cooperation verdict will be given.

Naturally, guilty individuals would want nothing but to pass a lie detector test. Even though a polygraph result is not admissible in most courts, a deception indicated report is still bad for them.

This is when countermeasures come in handy for those who desperately want to pass the polygraph exam.

Simply put, countermeasures are things that subjects do in a deliberate attempt to distort the result to beat the lie detector test. Countermeasures can either be physical (biting the tongue, pressing the toe against a tack in the shoe, etc.) or psychological (thinking of one’s happy place, counting backward, solving a complex math problem, etc.).

Either way, according to an experiment on measuring the effect of countermeasures on the result of a polygraph, both physical and psychological countermeasures allowed around 50% of the participants to beat the exam.

Since countermeasures, when employed properly, can contaminate the result of a lie detector test, it’s no wonder why it’s not uncommon for guilty individuals to deploy them. As a matter of fact, it’s not just deceitful subjects who may rely on countermeasures to pass a polygraph test but also truthful ones.

According to a polygraph examiner, about 46% of all truth-tellers hooked up to a polygraph machine will attempt to use countermeasures in the hopes of making sure that they will appear honest.

No matter if you are innocent or guilty, using countermeasures does not guarantee a no deception indicated report. This is especially true if the polygraph examiner detects that you are deliberately trying to pass.

Discontinuation of the examination is always a possibility if you get caught.

Then there’s also the fact that you will get a purposeful non-cooperation report. PNC for short, simply put, means that the use of countermeasures was detected and confirmed by the polygraph examiner. Getting a PNC report could result in all kinds of things, including losing your eligibility for a sensitive job or participation in a probation program.

Do All Liars Fail a Polygraph Exam?

While being deceptive can cause subjects to fail a lie detector test, some individuals can lie and still pass the examination. Psychopaths, who are known to be very good at lying, can easily obtain a diagnosis of no deception. That’s because they do not feel any stress when telling lies, thus resulting in stable polygraph readings.

Despite what the name implies, a lie detector machine does not detect lies.

It can, however, record changes in certain psychological processes attributable to increased stress levels, which can be due to a number of things. And one of them includes lying.

According to brain scans, psychopaths are capable of being deceptive with very little to no cognitive effort. This enables them to stay away from panicking and activating their fight or flight response, which causes stress hormones to be released into the bloodstream to prepare the body for either combating or fleeing the perceived threat.

Due to the absence of the fight or flight response’s activation, the psychological processes of psychopaths practically remain the same, which is similar to those of people who are telling the truth.

With no significant changes in blood pressure, heart rate, respiratory activity and sweating, it can be quite easy for the examiner to give a no deception report — the individual, who happens to be a psychopath of which the polygrapher isn’t aware, is deemed being truthful during the examination even though he or she was lying all the while.

A forum on corrections research says that up to 40% of criminals are psychopaths.

Needless to say, the administration of a lie detector test is useless if the subject is a psychopath. It’s for this reason why known psychopaths are automatically disqualified from undergoing one.


No matter the reason for your being subjected to a polygraph test, answering every yes or no question the examiner will throw your way truthfully is the way to go. Although it’s not an assurance that it will spare you from failing the lie detector test, it can work to your advantage in most instances and avoid complications.

Always keep in mind that the result of a polygraph examination has no admissibility in many jurisdictions. And being honest with your past mistakes doesn’t mean right away that you will lose your eligibility for a sensitive job.

Related Questions

What should I do if I don’t understand the question during a polygraph exam?

If the question doesn’t seem to be clear and understandable, the examinee may ask the examiner to repeat the question, in many instances more than once. Because poorly worded questions can affect polygraph results, a trained and experienced polygrapher should be sought.

Can I say “I don’t know” during a lie detector test?

When undergoing a polygraph examination, the subject should answer either a yes or no only if sure of the answer. Otherwise, the examiner should be informed that he or she does not know the correct answer. If asked to speculate in order to provide a response, the subject should refrain from doing so.

Read Next: People Who Should Not Take a Polygraph Test

Disclaimer: The content is intended for informational purposes only and does not contain advice on criminal and investigative questions and inquiries. If you need professional help, please check with your state authorities.

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