The lie detector is actually a polygraph, and is usually referred to as a lie detector test in the United Kingdom, in America the home of the lie detector its known as the polygraph. A polygraph examination is also referred to as a psychophysiological detection of deception (PDD) examination. The lie detector is a scientific machine / procedure that measures and records several physiological indicators, these are sweat grand activity, blood flow, blood pressure, breathing and movement while an examinee is asked a series of questions over multiple lie detector charts depending on the format of the exam, results are taken from an average over the charts. Depending on the format of the lie detector test the results will be Deception Indicated for a fail or No Deception Indicated for a pass. A screening lie detector test would have the results of No Significant Reaction for a pass or Significant Reaction for a fail. In all lie detector tests there is a chance the result could be inconclusive, fortunately using the latest techniques there is only a four percent chance of achieving this result.
Lie Detector Results
The lie detector will show deceptive answers as they produce physiological responses that can be differentiated from those associated with non-deceptive answers during the test. There are, however, no specific physiological reactions associated with lying, making it difficult to identify factors that separate liars from truth tellers. Polygraph examiners should all use validated scoring techniques and a recent push in the industry has been to use computerised scoring as this can be more accurate. Lie Detectors UK use ESS scoring and whilst we always manually score the charts we also use the ESS Algorithm built into the Stoelting software, this acts as a double check and only increases accuracy, any issues at this stage we would refer for a full quality control with another examiner.
The Empirical Scoring System (ESS) is an evidence-based numerical scoring model for manual test data analysis (TDA) of psychophysiological detection of deception (PDD) test data from examinations conducted using comparison question test (CQT) formats founded on decades of research. The ESS is designed to provide the field examiner with a validated and reliable scoring model based on the simplest available solutions for which there is published evidence of validity to support all principles, assumptions and procedures. The simplicity of the ESS means that scoring skills are readily acquired by inexperienced scorers, easily retained by both experienced and inexperienced scorers, and easily understood when explained to non-polygraph professionals.
Lie Detector Accuracy
The lie detector aka polygraph was first invented in 1921 by John Augustus Larson, a medical student and a police officer from California USA. Later on Leonarde Keeler refined the polygraph making it portable and adding GSR, galvanic skin response in 1939. It was then purchased by and used by the FBI and was the prototype of polygraph as we know it today. However, the last twenty-five years have seen science and research and development allowing greater levels of accuracy for a polygraph examiner to achieve. A single issue test on modern equipment will achieve an accuracy level of between 92% and 96%.
In many countries, lie detectors are used as interrogation devices, the UK Government has over fifty polygraph examiners who test sex offenders, terror suspects and domestic violence abusers. In America many law enforcement and government agencies such as the FBI, CIA, NSA and many police departments use the polygraph to great effect. A lot of prospective employees are screened using a pre-employment lie detector test.
The control question test, also known as the probable lie test, is the test that the majority of qualified and experienced examiners would run, it was developed to overcome problems with the relevant-irrelevant testing method. Although the relevant questions in the probable lie test are used to obtain a reaction from liars, the physiological reactions that “distinguish” liars may also occur in innocent individuals who fear a false detection or feel passionately that they did not commit the crime.
Polygraph examiners, or polygraphers, are licensed or regulated in some jurisdictions. The American Polygraph Association sets standards for courses of training of polygraph operators and has 2800 members worldwide, it’s a sign the examiner is qualified and experienced. Different countries also have local associations such as the UK Polygraph Association in the UK.
All Lie Detectors UK examiners are members of the American Polygraph Association APA and the UK polygraph Association UKPA. This ensures accuracy as they use the latest equipment and techniques during a lie detector test.