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Lie Detector Test - How To Cheat The Polygraph

Updated on September 2, 2015

Lie Detector or Polygraph is a device used to monitor physiological changes in a human subject to determine whether the person is telling the truth or not.

  • It is used by police and other law enforcement agencies to test suspects or person of interest in a crime.
  • The polygraph is also used by certain covert government agencies to evaluate the authenticity of critical information or intelligence obtained from subjects in possession of such information.

Basic Working of The Lie Detector or Polygraph

  • The subject is hooked to the polygraph machine using arm pad, chest pad, finger clips and few other sensors to monitor the blood pressure and pulse rate while he/she has to answer a list of questions asked by the examiner.

  • Modern lie detectors are able to monitor changes in body temperature such as sweatiness of fingertips and level of voice stress.

  • Using the heart rate, blood pressure, temperature and stress levels, the machine plots a graph showing the fluctuations.

  • The examiner analyses the graph against each question/answer and marks them as pass or fail.


Baseline Setting - Crucial Part of Lie Detector Test

Before the polygraph test can begin, a baseline for the truth has to be established. For this, the examiner asks some general questions to the person undergoing the lie detector test, such as "what is your name", "how old are you", "which was your first job". These questions are known as baseline questions.

Results are plotted for answers to these baseline questions, which are then used for comparison during the actual polygraph test. If the heart rate or blood pressure shoots up by a significant amount from the baseline measurements, that answer is marked as a fail.

Correctly setting the baseline is the most crucial aspect of the polygraph test, without which the lie detector will be futile.


How Reliable is the Lie Detector Test?

The results of the lie detector test are accurate most of the times, but not always! The accuracy and ability to effectively assess the truth depends to a large extent on the following aspects:


a) How have the lie detection questions been framed?

It is ideal to ask questions in a blunt and matter-of-fact way. For example, something like "where were you on the night of the ..... ?" may not be a very effective question as it allows the subject to pause and think.

Instead, it may be much better to ask "did you kill XYZ?" simply because of the shock factor the question is likely to have on the subject.

b) The tone and attitude adopted by the examiner

The examiner needs to keep a calm and normal tone during the entire polygraph procedure. Lie detection test is the not same as interrogation, and therefore should not be treated that way.

Using forceful tone, suspicious behaviour or intimidation will induce unnecessary stress in the subject which may interfere with the polygraph results.

Let's Start with a Joke


How To Cheat The Polygraph

Every electronic equipment has some flaw or loophole that can be exploited, the lie detector is no exception.

There are various setbacks that can be faced while conducting a lie detector test, each of which can be exploited by an expert liar to cheat the polygraph machine.

Let us see why the polygraph results may not always be accurate and how these points can be used to manipulate the results.

Results of polygraph tests are NOT considered suitable to be presented as evidence in a court of law.

Though the probability of inaccuracy in lie detector tests is typically low, due to the various loopholes discussed below, polygraph results cannot be blindly trusted.


1. Manipulating the Baseline Results

The person being tested can cheat the polygraph by deliberately lying on the initial baseline questions. Since a lie typically increases blood pressure and quickens the pulse rate in a normal person, it sets a higher baseline. Now when he lies on the actual questions under scrutiny, his measurements are in sync with the baseline.

This is the most common technique used by an expert to cheat a lie detector test. This technique is taught to intelligence and military agents as a counter measure to protect intelligence in case of capture by enemy.


2. Intake of Barbiturates

Barbiturates are drugs which forcefully induce a tranquillizing effect on the mind.

If a subject has consumed any such drug in moderate doses, it will not be visible from outward behaviour.

But if he tells a lie, the fluctuations in his BP and pulse rate will be minimal due to the effects of the drug consumed.

Of course, taking a lie detection test under the influence of strong drugs is not an easy feat to accomplish and takes a very well-trained deception artist to pull it off successfully.

3. You are a Clinical Psychopath

If you are psychopathic by nature, a seasoned criminal or you have evolved into a sociopath, manipulating the lie detector test will come naturally to you. This is because you would either be a pathological liar as all psychopaths are, or you would have trained yourself in the art of lying and deceit.

In both cases, your body will display very minimal fluctuation in both pulse rate and blood pressure, because of your lack of emotions, coupled with a trained mind

Norman Bate's Alter-Ego Helps Him Pass The Polygraph Test


4. Personality Disorders such as Schizophrenia

There are numerous psychological disorders in which the patient gets confused between reality and imagination, schizophrenia being one of the well-known among them. In this disorder, the schizophrenic believes certain figments of his imagination to be real-life incidents. If such a person is subjected to a lie detector test, he/she may genuinely believe unreal incidents to be true.

Therefore, it is extremely important to check the medical history of a potential subject and ensure that he/she doesn't suffer from any psychological disorders.


5. False Alarm due to Nervousness

The person undergoing the test may be generally nervous and stressed by nature. Sitting in an interrogation room and being bombarded with questions can be quite unnerving even for an innocent person.

The anxiety in a chronically nervous person can easily quicken the pulse rate and raise the blood pressure, often triggering a false alarm even when a person is speaking the truth.

6. Forgetfulness while Recalling Incidents

Often under interrogation, people falter and have difficulty in recalling details of an incident under scrutiny. The pause and the struggle to recollect everything can build up tremendous pressure for the subject.

Couple Takes a Lie Detector Test


Like every other equipment, the lie detector has its advantages and setbacks. The only thing you need to do when taking a polygraph test (if at all you need to) is to keep your calm and answer questions after careful deliberation, especially during the baseline questions. This will ensure a more or less consistent physiological response to all subsequent questions.

NOTE: This article is meant purely as an informational source and in no way intends to promote lying during a polygraph test or tutor people on the art of deception.

© 2015 Ritu Temptor


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    • Larry Rankin profile image

      Larry Rankin 20 months ago from Oklahoma

      There are a number of ways to cheat a polygraph, but they all require quite a bit of skill.

      It seem the easiest way is to just be a psychopath. They tend to be able to do it with no aid whatsoever because their bodies don't respond the same way when they lie.

      Great hub!

    • temptor94 profile image

      Ritu Temptor 20 months ago from India

      You are right Larry, being a psychopath makes it easiest, and not just in lying, in so many other things. Emotions (the negative ones) and anxiety can be a big burden :P

    • Jeannieinabottle profile image

      Jeannie InABottle 20 months ago from Baltimore, MD

      This is really interesting. Now if I ever need to take a lie detector test, I know how to beat it. ;-)

    • temptor94 profile image

      Ritu Temptor 19 months ago from India

      LOL.. thanks Jeannie :) Hope you never need to take the test though :)

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