Polygraph Examination Procedure

Polygraph Examination Procedure

Polygraph device helps to reveal the truth from the lie. For this reason, a test procedure is performed on the accused or a person. At first the device sensors are attached to the chest and fingers of the individual. Then, the person responds to some questions and the device records psychological symptoms on the paper.

The main purpose of a polygraph examination is to see whether a person is telling the truth or lie.

In this article, you will study about lie detector test, the process of getting the test, the test questions, types of questions, accuracy of the test and test price. In addition, you will be informed about using polygraph test in the courts and the states.

What is polygraph test?

Polygraph test is a kind of exam with the help of polygraph device and a professional examiner in order to detect lie or truth by its results.

Theory of Polygraph Examination

There are three theories according to polygraph test:

  • Psychological Theory of Telling Lie

When a person tells lie, he shows involuntarily emotional and mental changes.

  • Psychological mood

When somebody tells lie, maybe he scares from the issues that threat his ideal life. Therefore, fears and anxieties are the main mood. Similarly, the greatest psychological agent is fear.

  • Psychological Theory of the Questions

The administer designs polygraph examination and its questions in way that it will make a threat to the security of the person’s life.

Evaluation of changes

The administer who takes the exam, has to monitor the physiological changes that happen during the test process. These physiological changes are as follows:

  • Respiratory System – breathing rate
  • GSR – Perspiration and sweat
  • Cardiovascular System – number of beats/pulses and blood pressure
  • And other psychological signals of the person such as the arm and leg movement, fear and anxiety and so on.

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Stages of Polygraph Examination

There are three stages to polygraph test:

  1. Pretest
  2. Chart Collection
  3. Post-test


The most significant part of polygraph test is the pre-test. In most cases, the accused is anxious, nervous, angry, suspicious and fearful. The aim of the pre-test is to cumulate enough information to prepare the ques­tions of the test.

When pre-test starts, the examiner tries to communicate with the examinee. In this part, the examiner collects information. This information is related to past and present of the examinee. Because it is necessary for the examiner to know the examinee and for the examinee to be tested justly. Besides, no test is taken until a person is volunteer for the test. The volunteer should sign the forms of voluntary before the per-test starts. If a person uses alcoholic drinks, drugs or special medicine, or is physically not ready for testing, this person will be refused for testing.

On the other hand, the examinee should know the concept of polygraph test. Furthermore, the examinee must have information about what he/she is going to experience and how physiological responses show truth and lie. This will lead to have a better test experience. The examiner knows when psychological changes occur and correspondingly the polygraph records those changes. This section is an interview process and it’s not like an interrogation.

Types of Polygraph Examination Questions

Questions and Tests

There are only two kinds of tests:

  • Comparison
  • Non-comparison

Each test has several different types. The type of the test is based on the person’s character and circumstances of the case. There are four kinds of questions used for asking:

  • Irrelevant
  • Relevant
  • Control
  • Symptomatic

The examiner designed all the questions and entirely reconsidered with the examinee. Fundamentally, there are three kinds of questions. Irrelevant questions are formulated to demonstrate ordinary answers. Relevant questions are for administration of polygraph examination. Control questions used by examiner when the examinee answered equivocally. So, the examiner doubted about rightfulness of his ambiguous answers.

During the test, four to six sensors are attached to the person’s chest and fingers. Meanwhile, the administrator monitors the physiological changes by them. Then, the signals are written on a paper. Now, polygraph test converts to a cultural icon.

Polygraph Questioning Techniques

The majority of questioning techniques is based on comparing answers to commonly asked questions for investigation (relevant questions) against answers to other questions (comparison questions).

Most of the polygraph tests usually start with a pretest interview. In relevant-irrelevant test format, the examinee answers to relevant and irrelevant questions. Relevant questions are about the real issue of the case. But irrelevant question is about feelings stimulation (e.g., is today Saturday?). The first questions in the list belong to the irrelevant questions.

Comparison questions are also called control questions. These kinds of test compare the answers of the relevant questions with other questions.

The examiner designed all the questions and entirely reconsidered with the examinee. Fundamentally, irrelevant questions are formulated to demonstrate ordinary answers. Relevant questions are for administration of polygraph examination. Control questions used by examiner when the examinee answered equivocally. So, the examiner doubted about rightfulness of his ambiguous answers.

Frequently Asked Questions

The examiner asked 10 questions. Out of these 10 questions, there are three to four relevant questions and the rest are control questions. The examinee should answer all of them in yes or no. Here, there are some most frequent questions:

  • Are you 36 years old?
  • Is your name James? (kind of Control question)
  • Do you suspect anyone of stealing the car? (kind of Relevant question)
  • Is your dog’s name Shina?
  • Were you born in 1987?
  • Do you live on Hardestone Street in London? (Control question)
  • Asking misleading questions deliberately. For example, the question Are you 36 years old?. Absolutely a 36-year-old man would not have been born in 1987.

Chart Collection

The real polygraph examination is Chart Collection. In this section, the administer asks all the questions at least two times.  Usually, there are three charts which derived from the answering of questions. Also, Stimulation test is used for observing examinee’s answerability.


After completing the exam, the examinee may leave or wait for the results of the test. Actually, in Post-test, the examiner analyzes the test. Moreover, the examiner evaluates each question separately. Often, in order to evaluate the test, the examiner applies a computer algorithm and a numerical scoring system. Then, the examiner decided if the examinee was telling the truth or lie and even the test was result-less.

Time and results

Most polygraph tests take between 1 and 2 hours, but the examinee is attached to the device for only 15 to 20 minutes.

When you finish your exam, only thing you can do is to wait for your results. The results may take a while or do not spend a lot of time, so no one really can give a definitive answer to this question. If you have failed the Polygraph test and IIRC, you will be notified via e-mail.

You should consider that the examiners understand you have not had a faultless life. For example, minor infringement such as smoking small amount of marijuana when you were young does not mean that you do not deserve. Also, if it looks like you answered 1 or 2 questions unrealistically, that does not mean that you are not qualified.

Accuracy of the Polygraph Test

Is polygraph test accurate? Are the polygraph test results infallible? Has there ever been a case where the test result is wrong? Can someone beat a polygraph? Can someone cheat a polygraph? Is the polygraph test a good radix for judgment? Is there enough normative data to diagnose and distinguish between the guilty or innocent person’s reactions? Is there a probability of error in the test? How many percent errors does polygraph test have? These questions and researches about them can help to develop this technology and its ever-increasing advancements.

Among hundreds of studies about the human ability to detect lies, people have an average of 54 percent of the correct judgment. There was a common belief among people that those who detect lie in their professional lives (e.g., law enforcement officers), have more accuracy in judging for their training and experiences. In summary, the studies show that the accuracy of the ability to detect human lies is mediocre and inadequate for judgment. Besides the human ability, there should be a high-precision device to increase the percentage of accuracy.

In scientific terms, the aim of the polygraph test is not detecting lie. Actually, the polygraph test detects changes in psychological behaviors and signals. In a scientific sense, polygraph tests can be said to be valid. Published studies show that several valid polygraph methods have the accuracy of over 90% with a 95% confidence. Also, scientific reviews indicate that diagnostic tests have the accuracy of 89% with a confidence range of 83% to 95%. On the other hand, the criterion states of the target questions differ independently. Therefore, these polygraph tests provide lower accuracy. The test has accuracy near 85% and a confidence range from 77% to 93%. As a whole, it has been reported that the average accuracy of valid polygraph test is 87% with a confidence range from 80% to 94%.

As a result, the lower confidence range shows that it offers a more conservative view in the worst cases. Also, the claim that there is a high degree of accuracy does not match the volume of published evidence. On the other hand, there are discussions about cheating in a test or a test failure which has become a big concern. At least, we should remember that there is no perfect test.

Although, the result of the test can be useful to identify a person lying and a person telling the truth, it does not seriously mean that the lie detector test is error free. Maybe the questions are not adequate to accurately indicates how the individual reacts when lying. Moreover, the lie detector evaluates physiological signs which are related not only to the lying but also to anxiety. On the other hand, these physiological and vital signs can be due to the use of alcohol, drugs, certain medications or maybe illness.

Because of this, police officers and law enforcers cannot just rely on these kinds of test to prove the innocence or guiltiness. To conclude, it is substantial to consider the errors of the test. It can be concluded that the accuracy of the polygraph test depends on effective interviewing, effective test management, and the analysis of effective test data, good tools and questions as well as experienced and professional examiner.

So, what should we do? All the people owe to the inventors of polygraphs and they are responsible for continue their researches and investigations to develop new and more accurate version of polygraph device. There are always more subjects to learn. Psychologists and researchers are responsible for continuing their investigations. They should keep learning and utilize new emerging knowledge and techniques.

Polygraph Test in Court and States

Acceptance of the polygraph test as evidence in some courts is prohibited, and even referring to it in a testimony can lead to declare mistrial. Nevertheless, in accordance with the APA, polygraph tests are used in 26 states and some federal courts.

Courts do not accept polygraph test as obligatory, dependable and secure results as evidence in criminal trials. Even doing this test in family courts is not admissible as evidence. Testimony in court is not a simple task and it is based on the subject’s perception, recalling and explanation. The federal courts have their own rules for accepting the use of the results of a polygraph test as evidence.

According to the Website: legalmatch.com in the United States, some states such as California, Arizona, Georgia as well as Florida and etc., use polygraph test. Other states like New York, Texas, and Pennsylvania do not find polygraph test admissible.

Polygraph Test Cost

In general, the cost of the test depends on several factors, for example, the location of the test, the duration and the length of the test, the reason for the test and the examiner.

Polygraph tests are expensive because they are administered by professional and trained examiners. The cost of the test is usually a fixed amount that does not include extra costs. If you take a test in referral agencies, you should pay more costs; because they are as middleman and pay the referral fee.

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