Design And Construction Of A Lie Detector

Electrical Electronics Engineering | Engineering

The design and construction of a lie detector involve the intricate integration of various components aimed at discerning the veracity of statements. This apparatus typically incorporates a combination of physiological sensors, such as those measuring heart rate, respiratory rate, and galvanic skin response, to detect subtle changes indicative of stress or emotional arousal. These physiological signals are then amplified, filtered, and analyzed using sophisticated algorithms to distinguish between truthful and deceptive responses. Additionally, the construction of a lie detector entails meticulous calibration and validation procedures to ensure its reliability and accuracy in discerning deception. By leveraging advanced technology and physiological indicators, the design and construction of a lie detector endeavor to provide insight into the authenticity of verbal statements, aiding in investigative and interrogation processes.

ABSTRACT

Lie detection, also referred to as deception detection, uses questioning techniques along with technology that records physiological functions to ascertain truth and falsehood in response. The main aim of this study is to build a lie detecting device. This device is commonly used by law enforcement and it also has wider area of applications. This device was built around few electronics components such as transistors, resistors, capacitor, variable resistors etc. Lie detector was completely built and testing results show that this system can be used for interpreting person’s skin resistance or anxiety changes.

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

TABLE OF CONTENT

CHAPTER ONE

INTRODUCTION

BACKGROUND OF THE STUDY
PROBLEM STATEMENT
AIM AND OBJECTIVE OF THE PROJECT
SCOPE OF THE PROJECT
APPLICATION OF THE PROJECT
LIMITATION OF THE STUDY
DEFINITION OF TERMS

CHAPTER TWO

LITERATURE REVIEW

2.1 REVIEW OF THE STUDY

2.2 POLYGRAPH

2.3 BASIC APPROACHES TO THE POLYGRAPH TEST

2.4 REVIEW ON POLYGRAPH

2.5 REVIEW OF RELATED STUDIES

CHAPTER THREE

3.0 MATERIALS AND METHODS

3.1 SYSTEM BLOCK DIAGRAM

3.2 SYSTEM CIRCUIT DIAGRAM

3.3 COMPONENTS USED

3.4 CIRCUIT DESCRIPTION

3.5 CIRCUIT OPERATION

3.6 DESCRIPTION OF MAJOR COMPONENTS USED

CHAPTER FOUR

4.0 RESULT

4.1 CONSTRUCTION PROCEDURE AND TESTING

4.2 CASING AND PACKAGING

4.3 ASSEMBLING OF SECTIONS

4.4 TESTING OF SYSTEM OPERATION

4.5 CASING AND PACKAGING

CHAPTER FIVE

CONCLUSION AND REFERENCES
CONCLUSION

REFERENCES

CHAPTER ONE

1.0 INTRODUCTION

1.1 BACKGROUND OF THE STUDY

Lie detector also referred to as deception detection, uses questioning techniques along with technology that records physiological functions to ascertain truth and falsehood in response. It is commonly used by law enforcement and there are a wide variety of technologies available for this purpose. The most common and long used measure is the polygraph, which is considered by the U.S. National Academy of Sciences to be unreliable (Shu et al., 2012). The polygraph is a set of equipment that accurately measures various sorts of bodily activity such as heart rate, blood pressure, respiration, and palmar sweating. In recent years brain activity has also begun to be measured in this setting. This bodily activity can be displayed via ink writing pens on to charts or via a computers visual display unit.

The polygraph is widely used by analytical staff in a variety of medical and scientific settings for purposes other than lie detection. The system used sample data from two sensors collecting two distinct types of data.

It has been assumed that lying is accompanied by a change in the body physiological activity.

In lie detection situations, its use is based on the premise that lying is accompanied by changes in the activity measured by the polygraph. One of the major topics that psychologists and others have focused on across the decades is how best to determine if a testing procedure can be relied upon.

The overall objective of the work is to build a cost- effective lie detector monitoring device and to construct a prototype system with a low cost.

The principle is based on the human skin resistance, heart rate and body temperature that changes according to truthful response of subject to the questionnaire. If person lie, the skin conductance increases with increase of secretion from sweat glands thereby decreasing skin resistance. Other physiological parameters like the skin temperature and heart rate increases in response to lie by the subject. These physiological parameters are good indicators of subjects false and lie statement in the current work.

The concept behind this lie detecting system is that, we assume when a person lie he kind of pumps up his anxiety level which makes him sweat and develop moisture on his skin. We then use this piece of circuit to detect if there is moisture on his skin and based on the result we glow and LED, a green one for truth and red for lie.

1.2 PROBLEM STATEMENT

Detecting lies is crucial in many areas, such as airport security, police investigations, counter-terrorism, etc. Lying can be cognitively depleting, it can increase the risk that people will be punished, it can threaten people’s self-worth by preventing them from seeing themselves as “good” people, and it can generally erode trust in society (Levine et al., 2015). It is assumed when a person lie it pumps up his anxiety level which makes him sweat and develop moisture on his skin. However, detection of these changes can be difficult to detect with our physical examination, which is also labor intensive, time consuming, and inaccurate. A lie detector was built to overcome these challenges.

1.3 AIM AND OBJECTIVES OF THE STUDY

The main aim of this work is to build a lie detecting device. The overall objectives of the work are:

To build a cost- effective lie monitoring device.
To construct a prototype system with a low cost.

To develop technologies for a personal aid for mobility and monitoring.

1.4 SCOPE OF THE STUDY

The circuit is mainly designed to determine if subject were actually lying. The physiological parameters like skin resistance, skin temperature and heart rate are found to be the simplest and easily accessible parameters that changes accordingly in response to the questionnaire posed to the subject.

The scope of this study covers Development of a Lie Detection System using transistors, a capacitor, LEDs, resistors, and a variable resistor. The Lie Detector circuit is based on the fact that a person’s skin resistance changes when they sweat (sweating because they’re lying).

1.5 APPLICATION OF THE STUDY

This device is found to be useful to detect theft person by law enforcement. It helps in crime investigation and for counseling a person by psychiatrist.

1.6 LIMITATION OF THE STUDY

The prototype designed is found to be simple, portable and cost effective with good accuracy. But if the person subjected to the test is too confident about his responses then the test may not detect as there may not be any sweat or nervous feeling. The test may also fail if the subject is too tensed or mentally weak. In real time, the test can be performed with proper sedations to the subjects that may give more accurate results.

1.7 DEFINITION OF TERMS

Common terms attached to this work are defined as below:

FEAR – is emotional response to specific danger that appears to beyond a person’s defensive power.

STIMULUS – is a force or motion reaching the organism and excites the receptors.

REACTION – it is an action in mental attitude evokes by external influence.

DECEPTION – is an act of deceiving or misleading usually accompanied by lying.

DETECTION – It is an act of discovery of existence, presence of fact or something hidden or

obscure.

LYING – the uttering or conveying of falsehood or creating a false or misleading information with the intention of affecting wrongfully the acts and opinion of other.