Polygraph

1. Presented By -
Miss. Shivani R. Kale
Department Of Forensic Science
Shri Shivaji College Of Arts, Commerce &
Science,Akola.
Guided By -
Bhupeshkumar Nanhe
Assit.professor(Forensic Science)
Shri Shivaji College,Akola

2.  What is polygraphy
 A Brief History
 Defination
 Principle
 Instrumentation
 How Does It Work?
 Stages of polygraphy
 Use of polygraph
 Disadvantages
Legal Aspects
Case Study
Topics To Be Covered

3. What Is Polygraphy
Polygraphy is the scientific tool of
investigation. It is also called as a “Lie
Detector” & sometimes referred as a
psychophysiological detection.
 It is a process by which a study
of functioning of different
body system to detect lies.

4. Definition Of
Polygraph
It is an instrument which is
used to detect truth & deception
by measuring Galvanic Skin
Reaction(GSR),respiration rate,
pulse rate & blood pressure.

5. A Brief History
1. Cesare Lombroso - He invented polygraph in 1895 it
was made to record blood pressure & pulse rate.
2. John Larson – Discovered modern polygraph in 1925
which record respiration rate.
3. Leonarde Keeler – He was the co-inventor of
polygraph he made further modification to record
additional feature known as Galvanic Skin
Response(GSR).

6. Principle
It is based on the principle that if a person is
telling lie, & if there is a fear that the lie will be
detected, the emotional fear result in stimulation
of sympathetic nervous
system that cause
physiological changes
and some of this changes
can be recorded.

7. Instrumentation
• Cardio- Sphygmograph :- Collects blood
pressure and heart rate data.
• Pneumograph :- measures respiratory
patterns.
• Galvanograph :- measures electrodermal
activity or sweat.

8. How Does It Work?
• Polygraph machine records multiple(poly)
signals using four to six sensors and these are
recorded on a single strip of moving paper
(graph)
- Person’s breathing rate
- Person’s perspiration
- Person’s pulse
• This test measures
all the natural
changes caused by
ANS

9. Stages Of Polygraphy
 Pre-test interview :- Introduction related to
test.
 Chart preparation :- Three types of questions
are asked as :
1. Irrelevant
2. Relevant
3. Control
 Post interview :- Data analysis

10. Use Of Polygraphy
 Criminal Investigation.
 Industrial & Business Application.
Disadvantages
 Do Not Accurate.
 Not Admissible In Court.

11. This test is conducted in presence of
lawyer & preferably a doctor.
Must take the consent of accused.
Legal Aspects
Case Study
• Supreme court of india
Selvi & Ors Vs State Of Karnataka & Ana On 5
May ,2010
• Auother : K B I
• Bench : K.G Balakrishnan,R.V.Raveendran,
J.M.Panchal