Ian Duffield Polygraph & Lie Detection Services
This page includes general information about polygraph tests and the most common questions and answers about our polygraph / lie detector testing service.
Should I take a polygraph examination?

If you are thinking of taking a polygraph examination then something has happened in your personal circumstances that has made you think that someone you know has been deceptive or you have been accused of something that you need to diprove or refute. Taking a polygraph examination is a very serious matter and will inevitable change your life. Therefore, you should fully understand why you or someone you know wishes to take a polygraph examination and be completely aware of how the outcome of any test that you undertake will affect you directly or indirectly.

It is possible that you are looking for confirmation of innocence for yourself or someone you know or you are looking to provide information to resolve an allegation of theft, fraud or other criminal allegation.

Submitting to a polygraph examination should not be entered into lightly but with full knowledge and understanding that the results provided will be based solely upon the truthfulness of the individual taking the examination.


What is a polygraph examination?

The polygraph examination process will take approximately 2-4 hours during that time you will go through three phases.
  1. You will spend time with me and I will take you through a pre-test interview and develop and review all of the questions that you will be asked on the polygraph examination.
  2. I will begin by explain the polygraph equipment and sensors and will review in detail all of the questions that will be on the examination. I will then administer several tests to you in phases. During this time only you and I will be present to ensure that there are no outside distractions. 
  3. Once all of the examinations have been completed I will analyse the test data and will then be able to give an outcome of the examinee's truthfulness or deception before you leave.

How does the polygraph examination work?

The polygraph works by recording physiological changes to the body whilst answering questions that have been agreed upon prior to the examination beginning. These physiological changes are recorded using a number of sensors that are positioned onto your body and records changes in upper body movement, heart rate and blood pressure as well as sweat glands of the fingers.

This information is recorded onto the polygraph instrument and can be examined by the examiner to assess whether or not someone is being deceptive. The Polygraph cannot detect whether it is a small lie or a big lie but it will detect a lie based on the physiological changes that the body makes.


What sensors are attached to the body?

The polygraph instrument is attached to several sensors that are placed on the body. Typicall they are:
  • Pnuemograph - Two rubber pnuemograph tubes are placed around your upper chest and abdomen; these record body movement.
  • EDA sensors - The EDA (electrodermal activity) is traced by recording changes in sweat gland activity during the examination.
  • Cardiosphygmograph - This sensor traces changes in your relative blood pressure and pulse rate, and is similar to the blood pressure cuff your doctor uses to take your blood pressure.

How do you decide on the question and how many will I have to answer?

During the pre-test interview I will construct all questions that will be used during the examination. These questions are constructed based on the relevant issues that is under review. All questions are formulated using approved methods that adhere to the codes of practice sanctioned by the BPA and APA and meet strict rules to ensure question validity. I only use the latest and most appropriate techniques.

All questions are fully discussed for meaning and reviewed with the client prior to the start of any examinations. These questions are formulates so that they are direct, pertainate and relate only to the issue under examination.


Where will the test take place?

I am available to travel throughout the UK and will be able to travel to your location, travelling costs are fully inclusive within the price of the examination. Examinations must be administered in a quiet and distraction free environment and can be done within your business premise or if required at a local meeting room that I will arrange.

I am based in Thurrock, Essex - close to the Dartford Crossing. I am able to provide a distraction fee location where examinations can take place.


How much will a polygraph / lie detector test cost?

For an inclusive quote please call by business number on 07432 202724 between the hours of 9am and 9pm 7 days a week.


How do I choose the right polygraph examiner?

Your examiner should be qualified by the BPA and APA and have completed a minimum of 8 weeks training at one of the 30 accredited training schools in the world. If the examiner has attended and graduated from one of these approved polygraph training schools and is a member of the affiliated bodies the examiner is fully qualified to administer a polygraph examination.

Take the opportunity to speak to the examiner and ask them questions on where they trained and what associations they are a member of.


How reliable is the polygraph test?

The American Polygraph Association (APA) has gathered over 200 studies on the subject of test accuracy. You can view further details at the APA website.

APA Research results regarding polygraph testing vary depending on a number of factors some of which are laboratory study versus field study and inconclusive results being included or excluded. To help achieve a high accuracy rate the examiner you use should be a properly qualified individual using a validated and approved technique. Although no forensic testing of any kind can be guaranteed 100% accurate.


Do nerves affect the results of a test?

No. It is expected that anyone taking a polygraph examination will be nervous, whether they intend to be truthfull or not. Examiners look for responses over and above the examinee's normal heightened level of anxiety or nervousness
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