What Is an Infidelity Lie Detector Test?
An infidelity lie detector test is a structured, confidential session in which a trained examiner uses specialist technology to establish whether a partner has been truthful about suspected infidelity. The test is voluntary, private, and produces an objective result — a documented outcome that neither party produced and that neither party can argue was influenced by them.
In the UK, the most accurate form of infidelity testing available uses P300 EEG technology — a neurological approach that is fundamentally different from the traditional polygraph. Where a polygraph measures physical stress responses — heart rate, breathing, sweat — P300 EEG measures an involuntary brainwave that fires when the brain recognises something familiar. It fires at 300 milliseconds, before conscious thought, before anxiety, and before any deliberate response can be formed.
The result is a test that cannot be defeated by nervousness, coaching, or preparation — and that achieves 95% accuracy in real-world conditions, compared to approximately 51% for traditional polygraph methods.
The core question it answers
Does this person's brain recognise specific details about the suspected infidelity — locations, contacts, circumstances — that only someone who had the affair would know? If it does: deception indicated. If it does not: no deception indicated. The result is documented, objective, and produced by a source that neither partner controls.
Who Uses Infidelity Lie Detector Testing — and Why
People who book infidelity tests are not a single type. The situations that bring them to us are varied — but they tend to share one thing: verbal conversation has failed to resolve the question, and the uncertainty has become unsustainable.
The suspicious partner
Specific signs of infidelity — changed behaviour, phone secrecy, unexplained absences — have not been adequately explained. Denials have been given but have not resolved the doubt. The partner needs an objective answer, not another assurance.
The falsely accused partner
Someone who has been faithful but whose partner's suspicion is not resolving through verbal denial alone. A clear P300 result gives them documented, objective proof of their innocence — something no verbal assurance can match.
Both partners by mutual agreement
Some couples book mutual testing — both partners tested simultaneously — to remove the accusatory dynamic entirely and simply establish the facts. This framework is one of the most effective for preserving what can be preserved of the relationship.
After a previous admission or discovery
Where infidelity has already been admitted or discovered, but the full extent is disputed — one incident versus an ongoing affair, one person versus others — P300 EEG tests specific factual questions about the scope of what occurred.
Legal or separation proceedings
In some cases where infidelity has implications for divorce or financial settlements, a P300 EEG result provides documented supporting evidence for civil proceedings.
After a previous affair — rebuilding trust
Couples in recovery from a previous infidelity who want periodic verification as part of a structured trust-rebuilding process. Testing can provide the objective confirmation that verbal assurances alone cannot give.
How an Infidelity P300 EEG Test Works — Step by Step
Understanding what happens at each stage removes the anxiety of the unknown — which is one reason we share this information openly with both partners before any session is booked.
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Initial consultation — before anything is booked
You speak with us about the situation. We establish what the specific concerns are, what information is available for probe design, and whether P300 EEG testing is appropriate for your circumstances. This call is free, completely confidential, and there is no obligation to proceed. We advise honestly if testing is not the right step for your situation.
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Probe design — the key stage
We design the probe stimuli around specific details of the suspected infidelity that only someone who had the affair would have stored in memory — the location where meetings took place, specific contact details, dates, or circumstances. These must be details that have not been shared with the subject through prior conversations or confrontations. Probe integrity is everything: this is why we advise contacting us before extensive confrontations take place.
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Pre-test briefing with the subject
At the start of the session the examiner walks the subject through the process in detail — the headband, how the stimuli appear on screen, what the button responses mean, how long it takes, and when the result will be given. The general categories being tested are disclosed. The subject knows this test concerns suspected infidelity with a specific person or persons. The specific probe stimuli are not revealed in advance.
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The testing session
The subject wears the BrainBit EEG headband — lightweight, wireless, no discomfort, no gel. They view stimuli on a screen and respond with simple button presses. The session typically covers two to three question set areas and runs 60 to 90 minutes. It is calm, clinical, and private. There is no confrontation, no raised voices, and nothing unexpected.
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Same-day verbal result
At the close of the session the examiner delivers a verbal result directly — deception indicated or no deception indicated — for each question set. This is the moment the uncertainty ends. The result is based on the P300 waveform data captured during the session, assessed against established probability thresholds.
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Full written report within 24 hours
The written report follows within 24 hours. It includes the raw EEG waveform data, the methodology, probability scores for each question set, and the examiner's documented conclusions. A QR-verified result certificate is included. The report is formatted for personal, legal, or civil use as required.
What the Results Actually Mean
Deception indicated
The subject's brain produced a statistically significant P300 recognition response to the probe stimuli — details that only someone who had the affair would have stored in memory. This is documented neurological evidence of knowledge the subject has denied having. What the couple does with this result is their decision — confrontation, separation, counselling, or a combination. The test does not make that decision. It ends the factual uncertainty so that real decisions can be made.
No deception indicated
The subject's brain did not produce a recognition response to the probe stimuli. The infidelity being tested is not supported by neurological evidence. A clear result is one of the most powerful things an innocent partner can receive — objective, documented proof that their denial is consistent with what their brain actually holds. It ends the accusation on factual grounds rather than on trust.
Both results have value. A deception-indicated result ends the limbo of doubt and opens the path to real decisions. A clear result ends the accusation and gives the innocent partner something they could not get from any verbal exchange. Neither outcome is easy — but both are better than living indefinitely with unresolved uncertainty.
What to do if the result is not what you expected
A clear result for someone you were certain had been unfaithful is genuinely difficult to receive. It requires honest re-examination of what led to the suspicion — and in most cases, a sincere acknowledgement to the partner who was wrongly accused. Our acceptance guide addresses this situation directly and is worth reading before you book if there is any chance the result is not what you expect.
For guidance on what comes after a deception-indicated result, our post-result guide covers both outcomes and what each one means for the relationship going forward.
Cost, Coverage and How to Book
What it costs
Infidelity P300 EEG testing starts from £499 for a standard single-subject session. This includes the pre-test consultation, the full testing session, a same-day verbal result, and the written report delivered within 24 hours.
Where both partners are tested in the same session — mutual testing — pricing is per subject. Same-day appointments carry a priority supplement in most areas. Contact us for a specific quote based on your location and requirements.
UK coverage
We offer infidelity P300 EEG testing across the UK — London, Manchester, Birmingham, Leeds, Glasgow, Edinburgh, Liverpool, Bristol, Cardiff, Newcastle, Sheffield, and surrounding areas. Mobile testing is available for locations not covered by a fixed venue. See our UK coverage page for your nearest location.
Before you book
- Contact us before having extensive conversations about the specific details of the suspected infidelity — probe integrity depends on those details not being known to the subject in advance
- Both parties do not need to agree before you make an initial enquiry — speak to us first and we will advise on the best approach for your specific situation
- Consent must be voluntary — the person being tested must agree genuinely, not under duress
- Read our guide on partner refusal if the person you want to test is hesitant
Ready to Book — or Just Have Questions?
Speak to us before committing to anything. We will tell you honestly whether testing is right for your situation, walk you through the process in detail, and answer every question before a session is booked. The consultation is free.