If you have a polygraph examination coming up, it is entirely natural to feel uncertain about the process. This guide walks you through every stage — from the moment you arrive to the moment you leave — so that you can approach the day with a clear understanding of what will happen.
Key Points
- A polygraph session lasts a minimum of 90 minutes; most of that time is spent talking, not connected to sensors.[1]
- The examiner must review every test question with you before any recording begins — there should be no surprises.[2]
- You will be asked to give informed written consent before testing proceeds.[3]
- All phases of the examination must take place in person — remote or telephone polygraph testing is not permitted.[4]
- Attempting countermeasures does not help — it increases the risk of an inconclusive or incorrect outcome. The best approach is simply to be honest and follow instructions.
Before You Arrive
One of the most common questions people ask is whether they need to do anything special to prepare. The short answer is: no. There is no revision, no study, and no physical preparation required.
What to bring
- Photo identification. The examiner is required to verify your identity at the start of the session.[5] A passport, driving licence, or other government-issued photo ID will normally suffice.
- Any paperwork sent to you by the examiner or the commissioning organisation, such as appointment confirmation or pre-examination information sheets.
- A list of any medications you are currently taking, as the examiner may ask about these during the suitability assessment.
What to wear
Wear comfortable, everyday clothing. Sensors will be placed around your chest and abdomen, on your fingers, and around your upper arm, so loose-fitting tops with sleeves that can be rolled up are ideal. There is no need to wear anything formal or unusual.
Eating, sleeping, and medication
Eat and sleep as you normally would. Skipping meals or losing sleep is more likely to make you uncomfortable during the session than to help in any way. If you take regular prescribed medication, continue to take it as directed by your doctor — do not stop or alter dosages for the examination.
Arriving and the Testing Environment
When you arrive, you will be shown to a private room. The Standards of Practice require the testing environment to be reasonably free from distractions.[6] This means a quiet, enclosed space — typically an office or consultation room — where you will not be interrupted by noise, other people, or electronic devices.
The examiner will greet you, introduce themselves, and explain the process ahead. Their role is to administer the test in a neutral, professional manner; they are not there to judge you or to pressure you into any particular response.[7]
You should also be aware that the session will be recorded on audio and video.[8] This is a quality-assurance requirement and also serves to protect both you and the examiner.
The Pre-Test Interview
The pre-test interview is usually the longest part of the session. It covers several important steps.
Informed consent
Before anything else, you will be presented with an informed consent form to read and sign.[9] This form explains the purpose of the examination, how data will be collected and stored, and your rights during and after the process. If you have questions about anything on the form, ask the examiner before signing. For more about your rights, see Your Rights.
Identity verification
The examiner will check your photo identification to confirm you are the person scheduled for the examination.[10]
Medical and psychological suitability
The examiner will ask you about any medical conditions, medications, or psychological factors that might affect your ability to undergo the test comfortably and safely. This is a standard safeguarding step. Be honest and thorough — this information helps the examiner conduct the test properly and is treated confidentially.
Discussion of the issues
The examiner will talk with you about the subject matter of the test. This is your opportunity to explain your perspective and to ensure you understand what the test is about. This conversation also helps the examiner formulate clear, unambiguous questions.
Reviewing every test question
No surprises. The examiner is required to go through every single question that will be asked during the test, before any recording or data collection begins.[11] You will know exactly what you will be asked. If any question is unclear or you feel it does not accurately reflect the issue, raise this with the examiner — questions can be reworded for clarity.
Being Connected: The Sensors
Once the pre-test interview is complete and you are satisfied that you understand the process, the examiner will attach several sensors to your body. These are non-invasive and painless.
| Sensor | Placement | What it measures |
|---|---|---|
| Pneumograph bands (×2) | Around the chest and abdomen | Breathing rate and depth |
| EDA sensors | On two fingers of one hand | Electrodermal activity — tiny changes in skin conductance caused by sweat-gland activity |
| Cardiovascular cuff | Around the upper arm (similar to a blood-pressure cuff) | Heart rate, relative blood pressure, and pulse amplitude |
| Activity sensor | Typically on the chair seat or attached to you | Movement — used to ensure data quality |
All four sensor types are required under the Standards of Practice.[12] The examiner will explain each one as it is fitted and make sure you are comfortable.
The acquaintance test
Before the main test begins, the examiner will normally conduct a short acquaintance test (sometimes called a practice or demonstration test).[13] This brief exercise lets you experience what the questioning will feel like and allows the examiner to check that the sensors are recording properly. It is not scored as part of your result.
The Test Itself
During the test phase, the examiner will ask you the pre-agreed questions in a set sequence. You answer each question with a simple “yes” or “no.” There is a pause of at least 20 seconds between each question to allow the physiological data to stabilise.[14]
The same set of questions is typically repeated three to five times (known as “charts”). Repetition is an essential part of the methodology: the examiner analyses the consistency of your physiological responses across the charts.
Stay as still as you can. During each chart, try to sit still, breathe normally, and answer each question honestly. Deliberate movement can affect data quality and may require a chart to be repeated.
The entire examination — including the pre-test interview, sensor attachment, testing, and post-test conversation — will last at least 90 minutes.[15] In many cases it will last longer, depending on the complexity of the issues and the number of charts required. The examiner will remain neutral throughout.[16]
After the Test
Post-test interview
Once the data-collection phase is complete, the sensors are removed and the examiner may discuss initial observations with you. This is also your opportunity to raise any concerns, explain anything you feel is relevant, or ask questions about the process.
Results and the written report
The examiner will produce a written report of the examination.[17] Depending on the circumstances, the report may be provided to the person or organisation that commissioned the test. The examiner or the commissioning party will explain how and when you can expect to receive the outcome.
Confidentiality of your data
Polygraph data — including the physiological recordings, the audio/video record, and the written report — are personal data. They are subject to data-protection legislation, including the UK General Data Protection Regulation (UK GDPR) and the Data Protection Act 2018. The examiner’s obligations regarding storage, retention, and disclosure should be set out in the consent form you sign at the start. If you have any concerns about how your data will be handled, ask the examiner or consult the Privacy and Confidentiality Policy published by the BPS.
Tips for the Day
Be honest
The polygraph is designed to detect deception. The simplest and most effective thing you can do is to answer every question truthfully. If something is troubling you about a question, raise it with the examiner during the pre-test interview — questions can be adjusted for clarity before testing begins.
Follow instructions
The examiner will give you clear directions about how to sit, breathe, and respond during the test. Following these instructions helps ensure that the data collected are of high quality and that the test can be scored accurately.
Ask questions
If you do not understand something — whether it is a question on the consent form, a test question, or a sensor being attached — ask. A good examiner will welcome questions and take the time to explain.
Do not attempt countermeasures
Common misconception: “I can beat the polygraph by controlling my breathing, tensing muscles, or using other techniques.”
Attempting countermeasures does not work in the way people assume. The activity sensor and the examiner’s training are specifically designed to detect deliberate manipulation. Trying countermeasures increases the risk of the test producing an unreliable or adverse result — including a false indication of deception when you are, in fact, telling the truth. The best strategy is straightforward honesty.
Glossary
- Acquaintance test
- A short demonstration test conducted before the main examination, designed to familiarise the examinee with the process and to verify that sensors are recording correctly.
- Chart
- A single presentation of the full set of test questions while the sensors record physiological data. The same chart is typically repeated three to five times during an examination.
- Countermeasures
- Deliberate physical or mental techniques used in an attempt to manipulate polygraph results — for example, controlled breathing or muscle tension. These are prohibited and may be detected by the examiner and the activity sensor.
- EDA (Electrodermal Activity)
- Small changes in the electrical conductance of the skin, caused by sweat-gland activity. EDA is one of the primary physiological channels measured during a polygraph examination.
- Informed consent
- A signed written agreement confirming that the examinee understands the purpose of the test, the procedures involved, and their rights. Required before any polygraph testing may proceed.
- Pneumograph
- A sensor band placed around the chest or abdomen that records breathing patterns — specifically the rate, depth, and rhythm of respiration.
- Pre-test interview
- The structured conversation between examiner and examinee that takes place before the data-collection phase. It covers consent, identity verification, suitability, discussion of the issues, and review of all test questions.
- UK GDPR (UK General Data Protection Regulation)
- The UK’s domestic version of the EU General Data Protection Regulation, governing how personal data — including polygraph records — must be collected, stored, and processed.
- BPS
- The British Polygraph Society, an unincorporated UK membership body for polygraph examiners, founded in 2017.
- HMPPS
- His Majesty’s Prison and Probation Service, the executive agency that administers the statutory polygraph regime in England and Wales.
Sources
- British Polygraph Society (2020). Standards of Practice, v1.0. Available at: polygraph.org.uk/standards-ethics/standards-of-practice/.
This post is general guidance for members of the public. It does not constitute legal advice. If you are undergoing a polygraph examination as part of a statutory programme administered by HMPPS, the specific procedures and your rights may differ; consult your supervising officer or legal adviser. For further information about BPS standards, see the Standards of Practice.