How Does a Lie Detector Test Work?

It's just under a decade since the first reliable lie detector was invented and these devices have influenced the world of criminal investigations in many ways. In many places, you'll find lie detectors anywhere you'll find private investigators and these devices have even become important plot points in many fictional works.

The use of the term 'lie detector' among investigators has, however, led to a poor understanding of how these devices work. This has led to some people believing that these machines are infallible and others dismissing them as completely unreliable.

What Is A Lie Detector?

A lie detector is a piece of equipment used by private investigators and the police to determine if an individual is being truthful. The device consists of a number of electrodes which are attached to the body of the person being questioned by the investigator.

Analogue models of the lie detector have a pen that indicates the intensity of certain reactions on a continuous paper strip while digital models are connected to computers and reactions are reproduced on the screen where they can be easily analysed.

Who Uses Lie Detectors?

Lie detectors are mostly used by investigators, both private and in law enforcement. Although the evidence acquired from lie detectors is not admissible in court, it can help investigators in other ways such as narrowing down the list of suspects in a case or simply convincing someone that another party is being truthful about a particular issue.

Some of the people who regularly ask private investigators to carry out lie detector tests include:

Employers screening potential employees
Business owners conducting internal investigations
Spouses suspecting their partners of cheating etc.

Investigators in law enforcement have also started using lie detectors in a number of applications such as testing convicted sex offenders.

How Are Lie Detector Tests Able To Detect Lies

Lie detectors measure a number of physiological responses from the people being tested by the investigator. These typically include:

Breathing (diaphragm and chest)
Blood pressure
Pulse
Sweating
Body movements

The investigator first tests these responses when the subject is in a relaxed state i.e. when they are being asked control questions which are usually general questions with no relevance to the case. This helps the private investigator to form a baseline to which the second test will be compared to.

During the second test, the subject is asked questions which are relevant to the investigation. It has been observed that for most people, lying causes a great deal of stress and this results in an increase in the aforementioned body responses. Therefore, it is generally considered that the person isn't being truthful if there is a sudden increase in physiological responses when answering certain questions asked by the private eye.

However, private investigators often need to analyse the results of lie detector tests keenly before they settle on a particular conclusion. An increase in stress levels isn't always a sign that the subject is lying, it could simply mean that the person is stressed due to the experience of being questioned by an investigator.

This is where the experience of the private investigator can enable them to look at the results of the lie detector and also factor in the interviews before and after testing along with any other observations they made to decide if the person is being truthful.

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Where To Get A Lie Detector Test Done

United Kingdom

The United Kingdom, commonly Britain or the UK but officially the United Kingdom of Great Britain and Northern Ireland, lying off the north-western coast of the European mainland is an independent country. The United Kingdom includes smaller islands in the British Isles, the north-eastern part of Ireland and Great Britain. The United Kingdom is the 78th-largest ss in the world, with an area of 242,500 square kilometres. Although the kingdom of Great Britains official name from 1707 to 1800 was "Great Britain", the term "United Kingdom" has been used for it. The term "Britain" is used as a synonym for the United Kingdom and as a synonym for Great Britain.
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Commonly used to refer to matters relating to the United Kingdom is the adjective "British". Northern Ireland remained part of the United Kingdom. Approximately 243,610 square kilometres is the area of the United Kingdom. Throughout the 20th century, coupled with economic decline after world wars, as other nations industrialised, the United Kingdom heavy industry declined and began to lose its competitive advantage. By 1961 this number, just over 0.7% of the United Kingdom population, had more than quadrupled to 384,000. In 2006 the United Kingdom was the largest puplisher of books in the world and in 2005, 206,000 books were published.
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There are some sports in which the United Kingdom is represented by the Great Britain team, including the Olympics, where a single team represents the UK. The UK PC on Geographical Names stating that it has been used "informally", does not list "Britain", it lists "U.K. or UK" and "United Kingdom" as terms for the United Kingdom of Great Britain and Northern Ireland. A member of the Commonwealth of Nations amongst others is the United Kingdom. Sometimes referred to as the 'Scottish School of Common Sense' the United Kingdom is famous for 'Scottish Philosophy', and the 'British Empiricism'.
Investigating the UK

With plentiful rainfall all year round, the United Kingdom has a temperate climate. In October 2009, a new SC of the United Kingdom came. Her Majesty's Armed Forces - The forces of the United Kingdom consist of three professional service branches. With over 27 million arriving in 2004, Tourism is important to the British economy; London has the most international visitors of any city in the world and the United Kingdom is ranked as the sixth major destination in the world.
Searching For UK Sights

The total population of the United Kingdom in the 2011 census was 63,181,775. In the United Kingdom, forms of Christianity have dominated religious life for over 1400 years. In Ireland, then part of the United Kingdom, the Great Famine resulted in a million people migrating to Great Britain. With each county having a separate education system, education is a devolved matter in the United Kingdom.
Detectives in the UK

Together with holistic, alternative and complementary treatments, each country in the United Kingdom has its system of publicly funded and private healthcare and healthcare is a devolved matter. Sir Edward Elgar, RV Williams, William Byrd, Gustav Holst, Henry Purcell and Arthur Sullivan (most famous for working with the playwright Sit W.S. Gilbert) are notable composers of classical music from the United Kingdom and the countries that preceeded it. In the United Kingdom, a 2003 poll found that football is the most popular.

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I had an eerie feeling that someone was following me so I decided to contact Private Investigators. The entire team was extremely helpful throughout the entire investigation and they made me feel very comfortable and calm around them. I would always be grateful for their help!

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How Does a Lie Detector Test Work?

What Is A Lie Detector?

Who Uses Lie Detectors?

How Are Lie Detector Tests Able To Detect Lies

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