Polygraph test. All you want to know!

The polygraph test explained

Phases and steps of a polygraph test | Lie detector exam explained

Polygraph Test ExplainedPolygraph testing is a process in which a professional expert tests the statement of a person on a specific subject. Also known as lie detector test, polygraph tests are employed and applied all over the world in different fields and by an array of agencies, companies, and private people. It is, yet, a process that due to its popular applications, especially on television has been perceived as an almighty instrument capable of miraculously detect right from wrong. This, however, is not as easy as movies or TV shows portray. We will try to explain what polygraph testing is all about, what can be expected but most importantly, what cannot be required from a polygraph test.

Polygraph testing, how does it work

Polygraph testing is a structured process designed in such a way that the person examined can be tested on her/his statement about a subject, matter, issue or problem.

It is important to understand this distinction between testing or clearing a matter and examining independent questions. This is the biggest idea or should we say “myth” about a polygraph test that has been repeated every time again in movies and entertainment.

The result of a polygraph test is unique and does not discriminate among questions. The polygraph investigation analyzes someone’s honesty in a subject and not in questions.

Another wrong idea that is broadly used and spread is that one can connect an individual to the instrument and by asking a question the instrument will miraculously “spit out” if he lies or not to that question. This perception is far from true. Questions are asked on various occasions to make sure the physiological reactions are consistent and significant.

The normal steps of a polygraph test are the following:

1. Introduction of polygraph examiner and examinee to the test and case under investigation
2. Initial administrative paperwork is taken care of
3. Explanation of the polygraph instrument and process by the polygraph examiner
4. Explanation of the case by the examinee and follow up questions by polygraph examiner
5. Introduction to the polygraph questions
6. Physiological Data Collection phase (Examinee attached to the instrument and answering the questions asked by examiner)
7. Data Analysis (Chart analysis)
8. Discussion of test with examinee
9. Writing of polygraph test report with findings and result

Depending on the type of exam, time can differ from one test to another. Between 90 and 120 minutes should be taken into account from Step 1 up to and including Step 8. Report writing will depend on the examiner’s agreement with the client but can take anywhere between 24 and 72 hours.

How important is the instrument?

Analog-polygraphThe polygraph instrument is of course of importance when performing a lie detection test. Nevertheless, it is not as important as many people might think. If the polygraph examiner is using one of the major brands in the market, they will all have more or less the same outcome. Polygraph instruments have been around for a while and their measurements have improved over the years but they still read the same phenomena as the first instruments.

An instrument should at least measure the following:

  • Respiratory activity
  • Cardiovascular activity
  • Sweat activity / Skin conductance

Some instruments can have redundant accessories but any polygraph instrument used for detection of deception should at least measure these three channels.

The instrument can only register physiological activity. It is the right preparation, application of right stimuli in an adequate environment that will allow the readings to be indicative of truth or deception of the examinee.

A polygraph instrument is a tool permitting the professional to reach an opinion. It is in no way a “crystal ball” capable of telling when somebody is telling the truth or lying just asking random questions. To arrive to a reliable result a polygraph test needs to be run and applied following the steps explained before.

Different types of polygraph tests

Live polygraph testWhen referring to polygraph exams, these are often seen as one type of test. This is far from reality. The polygraph is used in different fields and for diverse reasons, needing distinct types of solutions and therefore techniques.

First of all, the polygraph can be used to detect knowledge about specific information or to detect somebody’s level of deception about a specific topic. These two types of applications will require different techniques:

  • The first will try to detect the highest physiological response among the elements presented to the examinee.
  • The latest will test the level of physiological response to stimuli and look for consistency and significance in responses.

The techniques used to detect deception through consistent and significant responses can then again be divided into screening or specific tests.

Screening tests are mostly used in cases like pre-employment, psychological treatment tests or post-conviction sex offender treatment programs.

Specific tests are the exams the public normally refers to. These test if a person is telling the truth or lying about a specific issue. These are also the techniques with the highest reliability rate.

Contact B.E.A.R. FORENSICSIf you need more information about polygraph tests you can also contact a representative.


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