What Is a Private Lie Detector Test?
A private lie detector test is a confidential, voluntary session in which a trained examiner uses specialist technology to assess whether an individual is being deceptive in response to a specific set of questions. It is booked and paid for privately — by an individual, a couple, a family, or a business — and the results are confidential to those present.
In the UK, the term "lie detector test" most commonly brings to mind the polygraph — the machine with attached tubes and wires that measures breathing, blood pressure, and skin response. That technology is still available from some providers, but it carries a well-documented accuracy problem that has prevented its results from being used in UK courts.
The technology we use at Deception Detection is fundamentally different. P300 EEG — electroencephalogram testing using the P300 brainwave response — measures something the polygraph cannot reach: an involuntary signal fired by the brain when it recognises something familiar, at 300 milliseconds after the stimulus appears. Before conscious thought. Before any deliberate response. Before anxiety, training, or effort can touch it.
A private lie detector test is not a dramatic confrontation. It is a structured, calm, clinical session that produces a documented result — objective evidence that neither party has the power to argue with, because neither party produced it. The brain did.
Who Uses Private Lie Detector Tests in the UK?
Private testing is more widely used than most people realise. The situations that bring people to us are varied — but they share a common thread: a specific question that verbal conversation has failed to resolve, and a need for something more definitive than a promise.
Relationship and infidelity concerns
The most common private booking. One or both partners want a definitive answer on infidelity suspicions after conversation has failed to resolve the doubt. A clear result ends the uncertainty permanently.
Family disputes and trust breakdown
Missing money, theft within a family, disputed accounts of events. Private testing allows families to resolve internal disputes without involving police or legal proceedings.
Workplace and business matters
Employers investigating theft, data breaches, or misconduct who want objective evidence before or alongside a formal HR process. Employees falsely accused who want to clear their name.
Legal and civil proceedings support
Solicitors and individuals seeking supporting evidence for civil cases, employment tribunals, or family court matters where P300 EEG results can carry evidential weight.
Insurance and fraud investigations
Insurers and individuals challenging or supporting the validity of a claim. Private testing provides documented evidence that can influence settlement decisions.
Personal matters and self-verification
Individuals who want to prove their own honesty — to a partner, a family member, an employer, or a court — in situations where their word alone has been questioned.
How a Private P300 EEG Test Actually Works
The name sounds technical. The process is straightforward. Here is what happens from the moment you make contact to the moment your report arrives.
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Initial consultation
Before anything is booked, we speak with you — and in most cases the person being tested — to understand the situation, establish what questions need to be answered, and make sure testing is appropriate. This is not a formality. It shapes the entire session. The questions we design are specific to your situation, agreed in advance, and reviewed before the test begins.
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Booking and preparation
Once a session is agreed, we confirm a date, location, and start time. We send preparation guidelines — what to avoid before the test, what to bring, and what to expect. Same-day bookings are available in most UK locations. Travel to your location can be arranged for situations where attending a fixed venue is not practical.
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Pre-test briefing
At the start of the session the examiner walks the subject through the process clearly — what the headband does, how the stimuli will appear, what the button responses mean, and how long it will take. All questions are reviewed and agreed before the test begins. Nothing appears without prior knowledge of the category being tested.
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The test itself
The subject wears the BrainBit EEG headband — a lightweight wireless device with dry electrodes that sits comfortably on the head without gel or preparation. They view stimuli on a screen and respond with simple button presses. Each question set runs for approximately 10 to 15 minutes. A full session typically covers two to four question sets. There are no surprise questions, no raised voices, and no confrontation. It is a clinical process.
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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 based on the P300 waveform data captured during the session and analysed against established probability thresholds. The verbal result is clear, direct, and delivered the same day.
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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 analysis methodology, the probability score for each question set, and the examiner's documented conclusions. The report is formatted for use in legal, HR, or personal contexts and includes a verifiable QR code linking to the result record. This is the document that carries evidential weight.
For a detailed step-by-step account of what the session feels like from the subject's perspective, see our full walkthrough guide.
P300 EEG vs Polygraph: Why the Difference Matters
If you have been searching for a lie detector test in the UK, you will have encountered both polygraph providers and P300 EEG providers. Understanding the difference between them is not a minor technical detail — it is the difference between a test that is affected by anxiety and one that is not, between a test that can be coached and one that cannot, and between accuracy figures of 51% and 95%.
| Factor | Polygraph | P300 EEG |
|---|---|---|
| What it measures | Physical stress responses — heart rate, breathing, blood pressure, skin conductivity | Involuntary P300 brainwave response to recognised stimuli |
| Affected by anxiety | Yes — anxious innocent people can produce false positives | No — P300 fires before anxiety reaches it |
| Can be coached or beaten | Yes — physical countermeasures are documented and effective | No — fires at 300ms, before conscious control is possible |
| Real-world accuracy | ~51% — barely above chance in independent studies | 95% across our UK case dataset |
| UK court admissibility | Not admissible in criminal proceedings | Carries weight in civil, tribunal and HR contexts |
| Physical comfort | Tubes, straps, finger sensors — physically attached equipment | Lightweight wireless headband — no gel, no discomfort |
| Subject anxiety impact on result | Significant — stress responses cannot distinguish guilt from fear | Zero — recognition memory is unaffected by nervousness |
The core distinction is this: a polygraph is measuring how you feel about a question. P300 EEG is measuring whether your brain recognises the information in the question as something it already knows. Those are entirely different things — and one of them is vastly harder to fake.
For the complete technical comparison, see our polygraph vs P300 page.
What Does a Private Lie Detector Test Cost in the UK?
Private P300 EEG testing starts from £499 for a standard single-subject session. This includes the pre-test consultation, the full testing session, same-day verbal result, and the written report delivered within 24 hours.
What affects the price
- Number of question sets — a standard session covers two to four question set areas. Additional areas extend the session and are priced accordingly
- Number of subjects — couples or multi-subject investigations (such as a workplace with several employees to test) are priced per subject
- Location — testing at one of our venues is included in the standard price; mobile testing to your location may carry a travel supplement depending on distance
- Same-day booking — same-day appointments carry a priority supplement in most areas
What is always included
- Pre-test consultation with the examiner
- Full P300 EEG testing session
- Same-day verbal result
- Full written report with raw waveform data, methodology, and probability scores
- QR-verified result certificate
- Complete confidentiality — results shared only with those present
The most common question we receive about cost is whether private testing is "worth it." Our honest answer: for the people who book, the answer is almost always yes — not because the result is always what they hoped for, but because the uncertainty they were living with was costing them more than the test.
Is a Private Lie Detector Test Legal in the UK?
Yes. Private lie detector testing is entirely legal in the UK. There is no law prohibiting a private individual from arranging or participating in a voluntary testing session.
The important qualifications are these:
- Testing must be fully voluntary — a test conducted under coercion or duress is not valid and could expose the person requesting it to legal liability
- Results are not automatically admissible in criminal proceedings in the UK — no lie detector evidence is, regardless of the technology used
- P300 EEG results can carry evidential weight in civil proceedings, employment tribunals, HR investigations, and family court matters, where the standard of proof is the balance of probabilities rather than beyond reasonable doubt
- The report must be produced by a qualified examiner and properly documented to carry any formal weight — ours meet this standard as standard
For a detailed guide to how P300 EEG evidence is used in UK legal and employment contexts, see our court admissibility guide and our solicitor's guide to P300 evidence.
Book a Private Lie Detector Test Anywhere in the UK
Same-day appointments available. Verbal result the same day, full written report within 24 hours. Completely confidential. Speak to us before committing to anything — the consultation is free.