Skip to content
Home » Putting Lie Detectors on Trial

Putting Lie Detectors on Trial

Wouldn’t it be wonderful If you could detect who is lying? However, most conventional methods of detecting lies, such as polygraph machines are no better than pure chance. While polygraph machines aren’t accurate in determining if a person is lying They can monitor the respiratory, cardiovascular, and electrodermal activity very precisely!

A brief overview of Lie Detection Techniques

One early method of lying detection was hypnosis. It has been employed in a formal capacity from the 1840s. It was regarded as a form that was artificially inducing sleep the practitioners believed that those who were hypnotized would be more honest in this naive (and plausible) state. In addition to the questionable ethicality of this method it was also not reliable in its results.

In the early 1900s when a doctor administered the drug scopolamine (or “twilight asleep”) on patients discovered the effect of it on them. It made them disclose personal details. This led to the development of a field known as narcoanalysis. In the use of barbiturates, such as sodium pentothal and sodium amytal were administered to those who were being interrogated in the form of “truth serum”. The idea behind this procedure was that psychoactives lowered the person’s defenses, which makes it more probable for them to open up. Certain forms of narcoanalysis are still in use today, but not in the majority of well-established democratic societies.

The History of Lie Detector Test

In 1921 in 1921, the 1921 California police officer called John A. Larson developed an instrument which could simultaneously track changes in heart rate, blood pressure and respiration. It was known as the polygraph, or more commonly called”the lie detector. The mechanism could be traced back to two previous advancements:

It was 1914 when Italian scientist Vittorio Benussi wrote Die Atmungssymptome der Lüge his research findings on the effect of lying on respiration function
It was 1915 when American psychotherapist William M. Marston created a continuous systolic blood pressure test to detect deceit

Larson tried his devices and methods using real cases from the precinct, however, his aide, Leonarde Keeler, refined the test procedures and made the device more portable and added an additional element to determine the galvanic skin response of the person being tested.

The Trial of Lie Detectors

The year 1923 was the first time William M. Marston tried to get the results of the lie detector test accepted as evidence before the courts of law, in what was later known as the case of historical significance United States v. Frye. The court ruled against the results of the lie detector which established the Frye standardthat could set a norm for the acceptance of experts’ evidence before U.S. courts for years to be.

Forty times later, back in the year 1965 in 1965, in 1965, the United States Committee on Government Operations carried out the first comprehensive examination of the polygraph test machine, concluding it was not reliable in detecting deceit as it was scathingly stated in the opening paragraph of this blog. At this point, however those who supported this test continued to go at full speed, unaffected by the committee’s findings.

Another significant update occurred in 1983, as U.S. president Ronald Reagan issued the National Security Decision Directive 84 that allowed federal agencies to utilize polygraphs in their work. In a surprising (and embarrassing) change President Reagan revoked the directive three months later, due to an unfavourable evaluation of the method conducted from Office of Technology Assessment. Office of Technology Assessment.

The Fundamental Science Behind Polygraph Tests

Polygraph tests monitor three bodily responses that are commonly connected to deceit:

Cardiovascular activity
Respiratory activity
Electrodermal activity

Cardiovascular Activity

Blood pressure, heart rate and other cardiovascular processes can be affected by the activities often associated with lying like responding to an anticipated or perceived threat (“fight or fight or” action) and the increase in mental activity. Polygraphs monitor cardiovascular activity using the wrist, arm, or finger cuff that is equipped with a sphygmomanometer. It functions in a similar way to the ones that are used in medical facilities.

Another method of measuring cardiovascular health is photoelectric plethysmographs. These are attached to the patient’s finger or ear, and transmit infrared radiation through the tissue. Photosensors measure light that is reflected or absorbed across the tissues. This directly relates to the volume of blood that it went before it reaches the sensor. This permits the physician to monitor changes in blood volume without having to use an instrument to measure pressure.

Click here for lie detector UK.

Respiratory Activity

Changes in the respiratory activity of the body could also be a sign of deception However, as breathing is easily controlled by the nervous system’s central nerve the test is considered to be less reliable.

The respiratory activity is assessed by attaching pneumatic rubber bellows to the abdomen and thorax. Inhalation and exhalation both expand the bellows and cause modifications in the thoracic as well as abdominal circumference. The changes in internal pressure are measured using the help of a pressure transducer.

Electrodermal Activity

Electrormal activity measurement is believed to be the most reliable and sensitive of the three tests. Why? It is because the skin’s electric resistance as well as conductance are mostly determined by the eccirine glands which are responsible for generating sweat. It is managed by sympathetic nerve system.

Electrodermal activity is monitored using two electrodes connected to the palm or fingers of the subject. A tiny current is applied, which is used to measure the conductance of the skin and any changes and how often the skin responds to spontaneous reactions as well as the amplitude of events-related responses and many other aspects.

In detecting deceit, you can get deceiving results

The polygraph monitors the subject’s physiological reactions in real-time by using the use of a line graph that contains three values which correspond to the respiratory, cardiovascular, and electrodermal outcomes. But, is it true that the results of the physiological tests can be used to answer the psychological dilemma as to whether the individual is lying? It is an open question.

One of the biggest problems with the accuracy of polygraph tests is that the physiological reactions to the test may vary greatly between individualsor even among the same person under different conditions. Additionally, breathing patterns can alter the rate of their heart and their galvanic skin responses. Individuals who work on breathing techniques and mindfulness can even control the physiological reactions (typically to control stress but they could be as deceiving as they can! ).

Therefore, if tests using polygraphs are not reliable, what alternatives can be used to detect deceit? Criminal justice and law enforcement professionals frequently employ advanced interrogation methods, where the polygraph is employed mostly as a mental aid to the interrogator and not as a reliable and proven detector of deceit. Advanced interrogators are even trained in facial microexpressions as well as non-verbal signals. While these methods are difficult to quantify, investigators’ instincts are more trustworthy over “chance”.

Making Better Physiological Testing Devices

A few blood pressure test devices aren’t used just to detect if people are lying. They are actually an vital to medical science and blood pressures are usually measured every when we visit an office of a doctor.

Certain blood pressure monitoring devices function by using piezoresistive pressure sensors. They are one of the most common MEMS devices that is based on the piezoresistive effect. This is when the electrical resistance is altered after the application of force to the semiconductor.

When developing an instrument to monitor blood pressure it is essential that the piezoresistive pressure gauge can accurately measure the blood pressure of the patient in a manner that is safe to the individual. It is therefore crucial that the designers can describe the workings and operation of the devices. They can also forecast their behavior, and then test their performance prior to when they’re released to the market.