a machine designed to detect and record changes in physiological characteristics, such as a person's pulse and breathing rates, used especially as a lie detector.

1. Polygraph
Prepared by:
Niraj Bartaula

2. Polygraph Devices

3. Introduction
• Is scientific, diagnostic, instrument known as
lie detector.
• Appropriate to be called as truth verifier.
• Invented in 1921 AD by John Augustus Larson.
• Measures several physiological indices.
• Used by FBI and CIAA (US law enforcement
and federal government agencies).

4. How can a machine detects whether someone
is telling truth or not ?

5. Testing procedure
• At first pre-test than diagnostic question is
asked.
• 3 basic type of question:- 1) irrelevant 2)
relevant 3) control
• Passed if psychological response to diagnostic
question is larger than those during relevant
question.

6. Accuracy
• Very accurate however it is unreliable.
• According to APA (American polygraph
Associatiation) in 250 studies over 25 years.
Accuracy of polygraph is 90- 95%.
• Lie detector test cost 500 pound in UK and
400$ in USA.

7. How there recording made?
Two strain gauze is taken. One across chest
and another across abdomen.
Ability of skin conductivity is recorded by
placing electrodes pads on finger.
Cardio- vascular activity is recorded using
standard blood pressure cuff placed on
forearm.

8. Who should not take polygraph
test?
 Person with serious heart
condition.
 Pregnant women
 Mentally incompetence
 Nerve damage or paralysis.
 Any person who has stroke or is an
epileptic (person who is in pain,
headache, toothache)

9. For polygraph test
o Good night sleep.
o Don't consume alcoholic beverage.
o Don't use illegal drugs for 24 hrs prior to
examination.
o Injury , illness or physical condition that can
impact you.

10. Issues that a Polygraph test is done
• Criminal Investigation
• Abuse
• Sex Offenders
• Child Custody
• Personal Investigation
• Arson
• Infidelity

11. How to pass Polygraph Test?
• Remember that polygrapher is not your friend:-
• Beware of pre-test tricks:-
• Conceal your knowledge of polygraph:-
• Don't believe in rumour:-
• Answer firmly, seriously and without hesitation:-
• Biting tongue is highly affective:-
• Change breathing pattern when control question
is asked:-
• Handle the post test interview:-

12. In Context Of
Confession of truth using such method is the severe
violation of human right .
 Confession are obtained using 3rd degree interrogation
methods like merciless beating, deprivation of water and
food, questioning in dark room etc.
So nepal police alternative to 3rd degree treatment is
Polygraph test.

13. Result Of Polygraph In Nepal
• Upto now 12-13 incident has been investigated by
polygraph in Nepal.
• Mahendranagar :-Unidentified mask people looted 2
crore 31 lakhs
• Ramananda chowk of Janakpur : Bomb blast incident by
Sanjay saha (CA Member) arrested by taking 2 hour
polygraph examination.
• Dhangadi: Nepal police used polygraph for carrying out
investigation into incident of looting about 4 crore of
Nabil bank by its own empolyee.

14. Conclusion And Discussion
 Polygraph lacks constitutional and scientific validity.
India supreme court has also banned to use polygraph
citing it is a violation of human right to life and privacy.
 Even in USA , land where polygraph is invented ,
Polygraphy has been banned by supreme court treating
it as unreliable.
 But in nepal nobody has been raising such question so it
is in practice.

15. Reference
• http://cib.nepalpolice.gov.np/ accessed on
12/03/2014
• http://www.webmd.com/ accessed on
15/03/2014
• http://en.wikipedia.org/wiki/Polygraph
accessed on 15/03/2014

16. Any Query?