The document discusses the polygraph, also known as a lie detector, outlining its history, functionality, and applications in forensic psychology. It reviews the accuracy and limitations of the polygraph, noting its controversial status in the legal system and susceptibility to manipulation. Advancements in technology have improved lie detection methods, enhancing their use in criminal investigations, courtroom settings, and ensuring a fair legal process.

1. SCIENTIFIC LIE
DETECTION AND
POLYGRAPH
By Aaradhya Soni
07/28/20XX
# FORENSIC PSYCHOLOGY

2. 07/28/20XX
01 INTRODUCTION
02 HISTORY
03 HOW DOES IT WORK
04 ADMINISTRATION OF THE TEST
05 EXAMPLES OF QUESTIONS
06 ACCURACY
07 LIMITATIONS
08 THE PRACTICAL APPLICATIONS
09 CONCLUSION
TABLE OF CONTENTS

3. INTRODUCTION
01
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4. INTRODUCTION
- Lie detector, also known as a polygraph
- Records physiological phenomena (blood pressure, pulse rate,
respiration) of a human subject.
- Operated during questioning to assess truthfulness
Utilised in police interrogation and investigations since 1924
- Controversial among psychologists
- Not always accepted as evidence in court
- Physiological indicators chosen are not easily controlled voluntarily
- Uses a pneumograph tube around the chest
- Utilises a blood pressure-pulse cuff on the arm
- Impulses recorded on moving graph paper driven by an electric motor

5. Respiration
CONCEPTS
Heart
Rate/Blood
pressure
Skin
Conductivity

6. HISTORY
02
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7. In ancient times, people
used trial by ordeal,
where accused
individuals faced
physical tests, hoping
divine intervention
would prove their
innocence. Swearing
oaths was another
method to establish
truthfulness.
Use of torture:
Interrogators employed
various forms of
physical torture to
extract confessions,
though the reliability of
such confessions was
questionable.
Ancient
Method
Renaissance
Era 18th Century
Franz Joseph Gall:
Developed phrenology,
which claimed to detect
deception based on the
bumps and contours of
the skull.

8. William M. Marston:
Created the systolic
blood pressure test, an
early precursor to the
modern polygraph.
Polygraph Invention:
John Augustus Larson and
Leonarde Keeler
developed the polygraph
machine, which measures
physiological responses
like heart rate,
respiration, and skin
conductance.
19th Century
Early 20th
Century
Mid 20th
Century
Rise of Polygraph
Testing: The polygraph
became widely used in
criminal investigations
and employment
screenings.

9. Cognitive Interviewing:
Psychological
techniques, such as
cognitive interviewing,
were developed to
enhance the accuracy of
eyewitness testimonies.
Functional MRI (fMRI)
and PET scans: These
technologies allowed
researchers to study
brain activity
associated with
deception, leading to
insights into the neural
basis of lying.
Late 20th
Century
Advances in
Neuroscience
Modern
Techniques
Computerised Voice
Analysis: Utilising
speech patterns and
voice analysis software
to detect deception.
- Eye-tracking
technology: Monitoring
eye movements and gaze
patterns to identify
signs of deception.

10. HOW DOES IT
WORK
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11. POLYGRAPH OVERVIEW
A. Tool for lie detection.
B. Measures physiological
responses.

12. Physiological
Measurements
I. Heart rate.
II.Blood pressure.
III.Respiration.
07/28/20XX

13. HOW DOES IT WORK
I. Polygraph machine records multiple
signals using 4 to 6 sensors attached to
the patient's body.
II.The person's breathing rate
III.The person's pulse
IV.The person's blood pressure
V. The person's perspiration

14. HOW DOES IT WORK
The Nervous System reacts to different situations differently.
For this, it uses different parts of it, namely:
I. Somatic Nervous System
II. Autonomic Nervous System
a) Sympathetic Nervous Systems
•Cardiosphygmograph: collects blood pressure and heart rate data
Pneumograph : measures respiratory patterns
Galvanograph: measures electrodermal activity or sweat

15. ADMINISTRATI
ON OF THE
TEST
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16. STEPS
Familiarizing
the subject
with the
test
Pre-test
Interview
Formulating
Questions
Analysis of
the result
01 02 03 04

17. EXAMPLE OF
QUESTIONS
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18. EXAMPLE OF QUESTIONING
QUESTION
TYPE
QUESTIONS RESPONSES
N1
Do you live in Evanston?
“YES”
C1
During the first 18 years of your life, did you ever cheat on an
academic assignment? “NO”
R1
Did you cheat on the Deception midterm?
“NO”
N2
Are you a psychology major?
“YES”
C2
Did you look at the answer sheet of the student next to you during
the midterm? “NO”
R2
Before starting college, did you ever copy someone else's work?
“YES”

19. 06
POLYGRAPH
-ACCURACY
(Vrij,2008)

20. ACCURACY
R/I:
a Extremely poor
CQT:
● 83-89% for guilty subjects
● 53-75% for innocent subjects
● 12-47% incorrectly classified
(falsely accused of guilt)
DLT (Raskin & Honts,
2002):
● Guilty- 73-84% depending on
type of directed lie
● Innocent- 84-87%

21. LIMITATIONS
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22. LIMITATIONS
1. Lie Detection Challenges: Imperfect accuracy despite
advancements.
1. Countermeasures: Vulnerable to manipulation, affecting
reliability.
1. False Results: Risk of labeling innocent or missing lies.
1. Ethical Issues: Privacy invasion, potential abuse.
1. Legal Dilemma: Admissibility and bias in court.

23. THE PRACTICAL
APPLICATIONS
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24. APPLICATIONS
I. Enhancing interview and interrogation accuracy.
II.Detecting deceptive statements.
III.Streamlining evidence gathering and suspect
identification.
IV.Evaluating witness credibility and mental state.
V. Improving ethical interrogation practices.
VI.Minimizing false confessions and miscarriages of
justice.
VII.Strengthening courtroom proceedings with additional
evidence.
VIII.Ensuring a fair legal process and reducing false
accusations.

25. CONCLUSION
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26. CONCLUSION
1. Psychology and Crime: Psychology helps us understand the motives
and behaviors behind criminal activities, informing crime prevention
and investigations.
2. Advancements in Lie Detection: Recent technological
advancements, including AI and brain imaging, have improved the
accuracy of lie detection methods.
3. Practical Applications: These advanced lie detection techniques
find practical use in criminal investigations, court proceedings, and
high-profile cases, enhancing fairness and accuracy in legal
processes.

27. CREDITS:This presentation template was created
by Slidesgo, and includes icons by Flaticon, and
infographics & images by Freepik
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07/28/20XX