Using a Lie Detector to Prove Innocence: What to Expect

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As people sought ways of forgiving themselves, different techniques and instruments have been used. Out of all these methods, one that has been receiving so much attention is the lie detector test. Even to this date seen in movies and TV shows as the literal truth telling machine, the polygraph or commonly known as the lie detector test claims to unmask the lie by measuring the physiological response.

To what extent is it really helpful and can it really aid in the effort to avoid a guilty verdict as much as possible? In this article, we are going to analyze the methods related to the lie detector tests; how the tests work, what is being measured, how the results are obtained and, finally, whether these tests will assist one to justify his innocence. 

What is a Lie Detector Test?

Polygraph, scientifically also known as the lie detector test, is an instrument that aims at determining and providing records of particular physical responses that are thought to be associated with lying. It has been in use since the early 1900s, and to this date, the polygraph machine is drawing attention, controversies, and criticisms. 

It is often used in cases where the researcher administers some questions to the subject while at the same time observing alterations in the subject’s body organs. The general concept of the polygraph examination is that the truth and lie have different arousal on the physiological and can be recorded by the machine.

How Does a Lie Detector Test Work?

A lie detector test involves the collection of several physiological indices including pulse rate, blood pressure, respiratory rate and skin conductivity. These indicators are measured through sensors that are placed on the subject’s body. 

In the test, the subject is presented with a number of questions concerning the issue under examination as well as filler questions that are irrelevant to the case. The answers to these questions are then used to set reference levels of the subject’s physical reactions while being truthful.

The polygraph machine then records any changes from this baseline that are exhibited by the subject when answering the relevant questions. The premise is that lying elicits feelings of stress or anxiety and that these feelings are accompanied by observable physical responses. The comparison of the answers to the questions with the baseline answers helps the polygraph examiner conclude whether the subject is lying or telling the truth.

What Does a Lie Detector Test Measure?

A lie detector test measures several physiological responses that are believed to be linked to deception. These include:

  1. Heart Rate: There is evidence that lying raises the most general indicator of stress and anxiety, which is the heart rate.
  2. Blood Pressure: This includes the physiological stress response to the act of lying, leading to an increase in blood pressure.
  3. Respiratory Rate: Decrease in respiratory rates, or even irregular respiration, can be the sign of lying in people, especially when they speak.
  4. Skin Conductivity: Sweating is a venerable sign of stress and anxiety and it is stated that the skin’s electrical conductivity enhances when the skin sweats. This is gauged by putting sensors on the fingers.

These physiological responses are then captured and used to judge the truthfulness of the subject’s answers.

How Are the Results Calculated?

A computer figures out the results of a lie detector test using the body’s responses. The person who runs the test looks for noticeable changes as the person answers questions. These deviations are interpreted as signs of deception.

The examiner uses a scoring system to quantify the degree of deviation from the baseline. A positive score typically indicates truthfulness, while a negative score suggests deception. The final result is based on the overall pattern of responses rather than a single response, as various factors can influence physiological responses.

Can a Lie Detector Test Help Prove Your Innocence?

Lie detector tests can help find the truth, but they don’t always prove innocence. Here’s why:

  1. Legality: In many places, Polygraph results can’t be used in court because they’re not reliable enough. So, even if someone passes the test, it may not help their legal case.
  2. Reliability: Lie detector tests are a contentious subject, and their efficacy is open to many questions to this date. Although supporters stress high effectiveness, claiming that the tests have accuracy rates over 90 percent, opponents note that, in certain situations, the tests can give false positive results, meaning that participants are labelled deceivers when in fact, they are not, or false negative results, where the test does not identify deceit at all.
  3. Supportive Evidence: Polygraphy can be employed when other types of proof are used as well since it is supplementary only in the process. For instance, the ability to produce a clean polygraph might reinforce your alibi or other elements of a pristine story.
  4. Personal and Professional Contexts: In civil, unlike criminal matters, polygraph tests can be applied in a personal or workplace to solve disputes or to check the credibility of a story. However, their effectiveness is contingent upon the tripartite agreement regarding the outcomes.

Advantages and Limitations of Lie Detector Tests


  1. Deterrent Effect: The prospect of taking a lie detector test can act as a deterrent for potential liars.
  2. Psychological Pressure: Knowing that physiological responses are being monitored can induce stress in deceptive individuals, potentially leading to more truthful responses.
  3. Support for Investigations: Polygraph tests can provide valuable information and direction for investigators when used alongside other investigative tools.


  1. Questionable Accuracy: The reliability of lie detector tests is not absolute, with accuracy rates varying widely across studies and contexts.
  2. False Results: Factors such as nervousness, medical conditions, or lack of standardisation in testing procedures can lead to false results.
  3. Legal Restrictions: The inadmissibility of polygraph results in many courts limits their utility in proving innocence in legal cases.

Preparing for a Lie Detector Test

Getting ready for a truth test is important to make sure it works well. Here are some things to remember:

  1. Stay Cool: Worry can change your body, so it’s important to stay calm.
  2. Tell the Truth: Answer all questions honestly to make a good starting point.
  3. Get Good Sleep: Make sure you’re not tired of the test to avoid tiredness-related body changes.
  4. Know What Happens: Learn about the test to feel less worried and more comfortable.

What to Expect During the Test

During the test, you can expect the following:

  1. Pre-Test Interview: The examiner will explain the test procedure, review the questions, and obtain your consent.
  2. Attachment of Sensors: Sensors will be attached to your body to measure physiological responses.
  3. Baseline Questions: You will be asked baseline questions to establish your physiological response patterns.
  4. Relevant Questions: The examiner will then ask the relevant questions related to the issue at hand.
  5. Analysis: After the test, the examiner will analyse the data and provide a conclusion based on your responses.


Lie detector tests, also called polygraph tests, help in understanding the place where technology and human psychology meet. Even though lie detectors can be useful for knowing whether one is lying; proving someone’s innocence using them is not final. 

There is continuous argument over which side should be taken with regard to the dependability of these tests, and obtaining permission from courts remains difficult. If you plan to undergo a polygraph exam to demonstrate your innocence, you must know the benefits.

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