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Infidelity Lie Detector Test
Booked directly with Lie Detector UK, and conducted by an examiner on the BPS and APA registers.
An infidelity polygraph examines up to three specific, factual questions that you agree in advance — not feelings, not intentions. It takes about two hours at a private office, costs £495 for one person or £695 for a couple examined separately, and produces a written report within 24 to 48 hours that goes only to whoever booked it.
A validated technique run by an accredited examiner sits at 95–98% accuracy. It is not admissible as proof in a UK criminal court, and it cannot tell you whether to stay. What it can do is stop you guessing.
Most people who book an infidelity examination are not looking for a surprise. They have been having the same conversation for weeks or months, they have been given an account that does not quite fit, and they need to stop guessing so they can decide what to do next.
This page covers what the examination actually is, what it can and cannot establish, how the questions are built, what happens on the day, what the three possible results mean, and what it costs. It is longer than a sales page because the decision deserves more than a sales page.
How common is infidelity, and how common is being wrong about it?
Around one in five British adults have admitted in survey research to cheating on a partner at some point, with men and women reporting similar lifetime rates — roughly 20% against 19%. Among those who admit affairs, the most common partners are friends (43%) and work colleagues (38%).
Source: YouGov survey research, summarised in our UK infidelity statistics.
Two things follow that matter before you book.
Suspicion is far more common than infidelity. Most people who worry about it are wrong. That is not reassurance — it is the reason an examination is worth doing rather than continuing to search a phone. An honest partner has no way to prove a negative, and the accusation itself does damage whether or not it is true.
Divorce statistics cannot be read as a cheating rate. Since 6 April 2022, divorces in England and Wales proceed under no-fault rules, so adultery is no longer cited as a ground. Anyone quoting divorce figures as evidence of infidelity trends is using the wrong number.
Source: Office for National Statistics, on the Divorce, Dissolution and Separation Act 2020.
Who books this
- One partner, privately. Suspicion has become impossible to live with and talking has stopped resolving anything.
- Both partners together. A partial admission has been made — “it was only a kiss” — and the extent is disputed.
- The accused partner. Someone telling the truth who is not believed, and who wants it examined rather than argued about.
- After a confession. Something has been admitted and the question is whether the admission is complete.
That third group is larger than most people expect, and it is the one the industry talks about least. Being disbelieved when you are honest is its own kind of difficult, and an examination is one of the very few routes out of it.
What an examination can and cannot establish
It can examine
- Whether physical contact took place with a named person
- Whether contact occurred during a stated period
- Whether a specific account you have been given is accurate
- Whether money was spent or concealed in a described way
- Whether contact has continued since an agreed date
It cannot examine
- How someone feels about you, or about anyone else
- Whether they regret it
- Whether it will happen again
- Anything the examinee does not themselves know
- Vague characterisations like “were you unfaithful”
The dividing line is simple: a polygraph records physiological responses to questions of fact. “Do you still love me” has no factual answer for an instrument to record, and no examiner should take your money to pretend otherwise.
The questions are the examination
This is the part people underestimate. The instrument is standard; the question set is what determines whether the result means anything.
You get up to three relevant questions, agreed with your examiner during the pre-test consultation and seen by the person being examined before the day. Nothing is asked on the day that has not already been approved by everyone involved.
Questions must be specific, bounded in time, and answerable yes or no. Compare:
| Not testable | Testable |
|---|---|
| “Have you been unfaithful?” | “Since January, have you had sexual contact with anyone other than me?” |
| “Do you have feelings for her?” | “Did you kiss Sarah on the night of the work party?” |
| “Are you hiding anything?” | “Have you deleted messages between you and David in the last month?” |
| “Will you do it again?” | “Have you had any contact with David since we agreed you would stop?” |
“Unfaithful” means different things to different people, which is exactly why it produces a worthless answer. Your examiner will help you define the acts and the period precisely. That conversation is uncomfortable, and it is the part that makes the examination work.
If you want a fuller sense of how these are constructed, we publish worked examples of infidelity and sexual contact questions.
Which format is used
We use one of two question formats recognised by the American Polygraph Association: the UTAH, a single-question test, or the AF/MGQT, a three-question format. Both are validated and heavily researched, which is precisely why we cannot deviate from them or bolt on extra questions on request.
Which one your examiner selects depends on how many distinct issues you need addressed. One tightly defined question examined well is worth more than three vague ones.
When two people are examined
A couple examination is £695 and covers both of you. You are examined separately, one after the other, in the same appointment — a third party in the room invalidates an examination, so you cannot sit in on each other’s.
Each of you agrees your own questions. Neither is asked anything they have not already seen. In practice couples book this for one of two reasons: both want to clear the air, or one has been accused and wants the accusation tested in both directions.
Consent must be given in writing on the day and can be withdrawn at any point, including once the instrument is attached. If the only reason someone is attending is that the relationship has been made conditional on it, the result will not tell you what you want to know.
A refusal is not a result, and it should not be treated as an admission. People decline for reasons that have nothing to do with guilt — anxiety, a medical condition, or simple objection to being tested by a partner.
Who cannot be examined
Not everyone is suitable, and a responsible examiner will say so before taking payment. The American Polygraph Association’s model policy lists conditions that make someone unsuitable:
- Active psychosis or an unmanaged psychotic condition
- Functional maturity below the equivalent of twelve years old on psychometric testing
- Severe intellectual disability, with an IQ below 55
- Acute severe mental health conditions, or a need for continuous assistance
- Observable impairment through alcohol or drugs
Source: APA Model Policy for Examinee Suitability, 9 September 2021.
Beyond that list, your examiner is assessing during the pre-test interview whether the examinee can think in the abstract, follow why the test is being run, understand right and wrong and the consequences involved, and reliably distinguish a truth from a lie with clear examples of each.
What happens on the day
- Arrival You give a first name at reception, nothing more. Identification is checked privately and you sign a consent form. Offices are ordinary private rooms — not clinics, and nothing on the door refers to polygraph testing.
- Pre-test interview The longest part of the appointment. Your examiner reviews the agreed questions one final time, explains exactly how the instrument works, takes a medical and medication history, and establishes your normal responses.
- The examination Three channels record continuously — breathing via two pneumograph tubes, pulse and relative blood pressure via an arm cuff, and skin conductance via two fingerplates. The instrument phase is the shortest part of the day. Only you and the examiner are in the room, and it is video and sound recorded for analysis.
- Scoring and result Your examiner scores the pattern across all three channels against your own baseline answers, then gives you the result before you leave. The written report follows within 24 to 48 hours.
Nervousness is expected and shows on every chart. It is not mistaken for deception, because the analysis compares your responses against each other rather than against some imagined calm stranger. Being anxious about an appointment that could end your marriage is not a finding.
The three possible results
| Result | What it means |
|---|---|
| No deception indicated | The charts show no significant reaction to the relevant questions. On a validated format run properly, this is a strong result. |
| Deception indicated | Significant, consistent reactions to the relevant questions across channels. |
| Inconclusive | The charts do not support a call either way. This is a real outcome, not a failure to report one, and an honest examiner will tell you rather than guess. |
Inconclusive results happen. Causes include medication, an unsuitable question set, illness on the day, or genuine ambiguity in the data. Where the cause is fixable, a re-test can be arranged — discuss it with your examiner rather than assuming.
Can it be beaten?
Countermeasures — controlled breathing, mental arithmetic, the tack-in-the-shoe trick — are what examiners are specifically trained to spot. Attempting them typically produces an inconclusive result rather than a pass, and the report will record that the examinee appeared to be manipulating the recordings.
For someone attending voluntarily to demonstrate honesty, that is a considerably worse outcome than the truth.
Accuracy, stated plainly
A validated technique, conducted properly by an accredited examiner, sits at 95 to 98 per cent. Anyone quoting 100 per cent is selling you something else.
Accuracy is not a property of the machine — it depends on things you can check before booking:
- Whether the examiner is registered with the British Polygraph Society or the American Polygraph Association. Both maintain public registers. Look the person up rather than trusting a logo on a website.
- Whether a validated question format is used, and whether the examiner will tell you which.
- Whether there is a genuine pre-test consultation, or just a booking form.
- Whether the examination happens in a controlled private room rather than your kitchen.
- Whether you receive a written report or only a verbal opinion.
Camera-based systems claiming to read deception from the eyes, voice-stress analysis, and phone apps are not validated techniques and do not record the physiological channels a polygraph records. If you are offered a “test” with no instrument attached to the body, no pre-test consultation and no written report, it is not a polygraph examination.
Preparing for the appointment
| Do this | Why |
|---|---|
| Sleep normally the night before | Fatigue affects the recordings |
| Avoid caffeine and other stimulants | They alter the cardiovascular channel |
| Abstain from alcohol and recreational drugs for 24 hours | Observable impairment makes someone unsuitable for examination |
| Take prescribed medication at its normal dose | Do not skip it. Tell us what it is when you book and we will advise |
| Eat normally | Attending hungry is a distraction, not a virtue |
| Be honest in the pre-test interview | It is where the questions are finalised, not a trap |
Source: APA Model Policy for Examinee Suitability, 9 September 2021.
Where the report stands legally
Polygraph evidence is not admissible as proof of guilt or innocence in a UK criminal court, and its use in civil proceedings is limited and at the court’s discretion. Nobody should book an examination on the understanding that it will decide a case.
Where a report genuinely carries weight is in the space around the courts: personal and family decisions, internal workplace processes, and situations where two accounts conflict and there is no other way to test them.
What you receive
Your examiner gives you the result before you leave, and the written report follows within 24 to 48 hours. It sets out the questions asked, the responses recorded, and the examiner’s stated opinion on what the charts showed.
The report goes to the person who made the booking and to nobody else without explicit written consent. If a third party needs to confirm a genuine examination took place, we can issue a pass code for that purpose rather than releasing the report itself.
Examiners are independent and report what the charts show. Nobody is told what they hoped to hear — which is the only reason the answer is worth having.
What the fee covers
| Included | Detail |
|---|---|
| Pre-test consultation | By phone, before the appointment, where the questions are agreed |
| The examination | Around two hours at a private office |
| Scoring and analysis | Scored against your own baseline across three channels |
| Written report | Within 24 to 48 hours |
| Travel | No call-out charge to any of our offices, and no per-mile fee |
£495 all inclusive for one person, £695 where both partners are examined. A £150 deposit reserves the appointment and comes off the total, with the balance due 48 hours beforehand. Scotland is priced separately at £695 and £850 and is arranged by phone.
Afterwards
Worth thinking about before you book rather than after: people are sometimes surprised by how little a confirmed answer resolves on its own, in either direction. An examination settles a question of fact. It does not decide what you do with it, and it is not couples therapy.
A result confirming infidelity does not tell you whether the relationship can recover. A result showing no deception does not repair the months of suspicion that preceded it. Both are useful precisely because they end the arguing about what happened, which is the thing that was making everything else impossible.
Booking
If you would rather talk it through first, call 020 8058 6848, Monday to Friday, 8am to 8pm. The consultation is free and carries no obligation, and if an examination is not the right answer for your situation we would rather say so on the phone than take a deposit.
Otherwise a £150 deposit reserves the appointment. There is no call-out charge for travel to any of our offices — find the nearest one, or read the questions people usually ask first.
Other formats
People also look at
Infidelity
Specific-issue testing on suspected physical or emotional involvement with someone else.
View format →False accusation
For people who need a documented, independent examination to answer an allegation.
View format →Theft
Workplace and domestic theft, tested individually rather than by group suspicion.
View format →Dispute resolution
Family and civil disputes where two accounts cannot both be true.
View format →Addiction
Abstinence monitoring, usually as part of an agreement between family members.
View format →Employee screening
Pre-employment and integrity testing for security-sensitive roles.
View format →Understanding lie detector services
What a real examination involves, and how to tell one from the things sold as lie detection.
View format →Common questions
The questions people actually ask us
How accurate is a lie detector test?
A validated technique, run properly by an accredited examiner, sits at 95–98%. Anyone quoting 100% is selling you something else.
Does being nervous affect the result?
No. Nervousness is expected and shows up on every chart. The analysis compares your responses against each other, not against a calm stranger.
What questions will be asked?
Up to three relevant questions, agreed with you in the pre-test consultation. Nothing is asked on the day that you have not already seen.
Can I refuse to take the test?
Yes, at any point, including once you are in the room. An examination in the UK cannot proceed without your written consent.
How long does the test take?
Around two hours in total. Most of that is the consultation and question review; the instrument phase is the shortest part.
Can I attend someone else’s test?
No — a third party in the room invalidates the examination. You are welcome to wait in reception and to see the written report if the examinee consents.
Do you offer home or on-site tests?
Tests are normally conducted at our private office in the UK, where the environment can be controlled. Alternative locations may be possible subject to pre-approval.
Do you test under 18s?
Only in limited circumstances, with the written consent of a parent or guardian, and at the examiner’s discretion. Please call to discuss before booking.
Do medications affect the results?
Tell your examiner what you take. Most prescriptions are fine; a few are not, and your examiner will say so before you pay the balance.
Can the test be cheated?
Countermeasures are what examiners are trained to spot. Attempting them typically produces an inconclusive result, not a pass.
How much does a lie detector test cost in the UK?
£495 all inclusive for one person and £695 for a couple, covering the consultation, the examination and a written report. A £150 deposit reserves the appointment.
