Campbell House
Polygraph lie testing

Polygraph Lie Test
How it works
Phases of the test

How it Works

Parameters Measured

Physiological parameters are monitored continuously with a polygraph instrument:

  • Respiration rate: breathing and chest movement is measured continuously by two pneumographs – components which includes two rubber tubes placed around the subject’s chest and abdomen, over the subject’s clothing.
  • Skin resistance: progressive changes in galvanic skin response is measured by means of two finger plates placed across two fingers of one hand.
  • Blood pressure, and
  • Blood volume: these are measured continuously by a cardiosphygmograph which uses an upper-arm cuff, similar to a blood pressure monitor.

These variables produce sets of concurrent traces on the examiner’s computer screen, and at the point in time when any of the questions are answered by the subject a special marker is attached to the trace.

Appointment Phases

Two phases are involved in an appointment session:

Phase 1

Phase 1 comprises an interview. This typically is the longest part of the test and the time for it varies depending upon the reason for the test.

The purpose is for the examiner to fully understand the underlying issues at stake, to agree and define the specific wording of the questions to be answered, and then to calibrate the computer equipment so that the electronics are individualised.

The examiner will make precise automated baseline measurements of the physiological parameters listed above and this baseline will then be tested with a whole range of questions or issues or feelings held either strongly or weakly.

The testing involves a computerised analysis of the subject’s physiological reactions to these.

Phase 2

Phase 2 is the actual test which commonly lasts about 30 - 40 minutes.

The critical questions (called Relevant Questions) are agreed between the client and examinee in advance. They will always be asked at a minimum of 3 times - typically in different ways - and interspersed with other questions designed to maintain baseline reference.

About the Examination

The Relevant Questions are formulated once the key issues in the case have been examined. The number of these Relevant questions are typically 3 and in order to achieve the highest test accuracy, all 3 questions should ideally relate to one subject, i.e, a single issue. This is known as a Single Issue test.

The Relevant Questions are always known by the examinee in advance, and the examinee must agree to be asked these. The test is a completely voluntary process and nobody can be coerced into either doing a polygraph test or answering questions they do not want to.

All polygraph questions require a yes / no answer.

It is not possible to cheat the test, either by clever thinking, hypnosis, meditation or by drugs, because in order to do so a person would need to have conscious control of their heart rate, blood pressure, skin resistance and respiration rate - ALL AT THE SAME TIME.

Deception is indicated by characteristic changes in one or more of the 4 variables, immediately upon the subject’s response to a question and for a short period following.

Truthfulness (i.e. absence of deception) is shown by the absence of any such changes in these four continuously monitored variables, and will be visible to the examiner as no change in the trace pattern at that point, immediately as the subject answers the question, and also immediately afterwards.

The professional skill of the examiner rests in the precise way in which any question is worded, together with his / her experience of knowing what trace variations are significant – and what variations are not.


  • Contact our office as soon as you know that you want to go ahead with a polygraph lie test.
  • Do not leave it until the last minute as our examiners get booked up.
  • A non-refundable deposit is required to book the test.

Do contact us if you have any questions.

Polygraph Test

  • Theft / Honesty
  • Employee vetting / Monitoring
  • Investigations

Lie Test

  • Matrimonial / Fidelity
  • Relationships
  • Abuse / Sexual abuse

The Subject

  • Written consent
  • Results confidential

UK Polygraph Services

  • Polygraph tests
  • Lie testing
  • Commercial and Domestic
  • National coverage

About the test

  • 1½ to 2 hours
  • Quiet location
  • Immediate results
  • Written report