All About Lie Detector Tests
A Polygraph test is commonly referred to as a Lie Detector Test, which is administered to check for deceptive physiological responses, when a person is answering questions while connected to polygraph hardware and software like the Lafayette LX4000. Polygraphs are not the only method of lie detection as methods of lie detection range from observing body language, micro expressions, oral and wording scrutiny and voice stress analyzing, however, polygraph is the most widely used with about 70,000 people being polygraph tested every year by the US Government (www.en.wikipedia.org/wiki/Polygraph). According to the scientific journal titled “Polygraph”, this type of lie detection test is the only modality that incorporates evidence based methods involving psycho-physiology.
What do polygraph machines measure?
A polygraph machine or instrument as it is called in the industry, records several graphical tracings of physiological responses such as variations in breathing, galvanic skin response and blood pressure. Responses to pre reviewed questions that trigger changes in a person's sympathetic nervous system are then contrasted to responses to other diagnostic questions, such as " Before 2008, did you ever tell a lie besides what you told me about?" The method of polygraph testing used by this firm is similar to that used in the United States and is termed psycho-physiological detection of deception. Voice stress analysis is another type of lie detector test, however proponents of polygraph such as this firm, are of the opinion that they are not as accurate as a polygraph. Lie detector testing is often portrayed in television shows, where a multitude of questions are asked for entertainment purposes, however an authentic polygraph test is very different, as it focuses on a single issue.
History of Lie Detection methods
Ancient methods of lie detection relied purely on the physical reactions of lying. People passed an egg around until the unfortunate person who dropped it, was called a liar because nervous reactions were perceived as guilty reactions. John Augustus Larson developed a prototype lie detector machine in 1921, based on a previous machine invented by William Marston. These polygraphs machines measured variations in blood pressure and breathing. Keeler made more progress with the polygraph machine in 1939 with what is considered the prototype of contemporary polygraph systems like the Lafayette LX4000. William Marston, the father of the polygraph started measuring changes in blood pressure to determine if someone was lying. In 1938 he wrote the book titled, "The Lie Detector Test" according to http://en.wikipedia.org/wiki/Lie_detection
Instructions on Taking a Lie Detector Test
A person scheduled to take a lie detector test should adhere to a routine of normality. Ensure sufficient sleep, rest and normal eating without consuming illegal drugs and alcohol so that a person will present as normally as possible for the polygraph examination and is comfortable during the test. While nervousness is normal, remaining totally truthful during the test is essential to passing a lie detector test. Being honest with the polygraph examiner will be helpful in addressing the matter. Do not control your breathing nor hold your breath or make movements when the questions are being asked. The polygraph test facilitator will review all the questions so that the person is familiar with the questions before the test begins.
Essential facts to know before taking a Lie Detector Test
Lie detector “machines” have appeared in the media, movies and television since world war two. The polygraph records three or more tracings of autonomic arousal of heart rate, blood pressure, breathing and galvanic skin conductivity. The amplitude, frequency and duration of breaths are measured by instruments on the chest and stomach. Cardiovascular data is obtained by a blood pressure cuff on the arm. Galvanic skin or response is measured through electrodes attached to the fingers.
The polygraph machine itself is only used during part of the polygraph examination. A typical examination includes a pre-test phase which is like an orientation where the process is explained and each question to be asked on the lie detector test is reviewed. The purpose of this stage is to ensure that the person being tested understands the questions. An acquaintance test incorporating numbers can be included as a demonstration of the instrument's accuracy in detecting a deceptive response.
The two most common types of question templates in lie detector testing in Australia, using the polygraph instrument
The most common validated test format for specific issue lie detector tests, according to the peer reviewed journal Polygraph is the Comparison Question Test (CQT). This form of test contrasts responses to relevant questions (e.g., "Did you kiss Jane?"), with comparison questions such (e.g., “Before you moved to Sydney, did you ever lie to someone who trusted you, besides what you told me today?”). These comparison questions are used as a control question for comparison against the ominous character of relevant questions. Comparison questions reflect actions that are similar to the allegation question, but are broad and time barred to a period prior to the alleged event for example, "Before 2013, did you lie to a mate?"
A truthful person who is innocent of the allegation will dread the comparison questions rather than the allegation questions. As comparison questions stimulate a person’s worry about their historic deeds, allegation questions relate to an action a person is confident they are innocent of. Graphical representations of greater physiological reactions to allegation or relevant questions in contrast to comparison questions results to a final call of deception indicated. In contrast, bigger and prominent reactions of respiration, skin conductivity and blood pressure to comparison questions results in a final call of no deception indicated.
Another validated lie detection procedure is the Guilty Knowledge Test (GKT), which consists of a multiple-choice exam regarding knowledge that would only be known to the accused or victim. For example, questions such as "Was a ring, a bracelet, or a necklace stolen?" A prominent physiological response to a series of correct answers would lead to indications that such a person appears to have intimate knowledge of the event that an innocent person would not. Constraints of the GKT are that that it cannot be used when the details of the incident have already been made public so everyone including the person taking the test would have intimate knowledge of the test. Polygraph “experts” in Australia should ensure that this is not the case before using this modality of polygraph testing. This firm conducts both of the above methods of polygraph examinations using best practice methods that the industry has to offer today.