Polygraph Test or we can also say that a lie detection test - It is a test used
to know whether a person is saying truth or lie by techniques.
So If I talk about this test , this test is not fully trustworthy, we cannot
believe on this test completely in a blind way, although by this test the truth
getting probability from the person accused of any particular crime, increases.
In this Test, a person is equipped with 4-6 sensors , and these are attached to
the body of person which I will be discussing next.
A Polygraph Machine is used in such type of tests, which measures the responses
or the signals which are provided by the sensors.
After the signals are recorded
Consequently, A graph is made, which ensures, did accused tell lie or truth? So
let's discuss about certain things1 which are recorded by the sensors of the
machine from the Person being tested.
- Blood Pressure
- Breathing Rate
These are the main factors upon which a person is tested for taking his
statement, whether there was any change or not ? Is seen into the graph.
Although it is not necessary that only the factors:
The list of these factors I have given above is not exhaustive, there can be many types of sensor signals also, have mentioned above are taken into account, there are so many other factors which can also be taken into consideration for examining the statement of a person like:
- Movement Of Arms
- Movement Of Legs
But these factors are not always checked, only the above mentioned factors are primarily observed.
3- Process of Polygraph Test (How it is done)
When the Polygraph test starts, First of all, a questionnaire is prepared by the examiner:
3 to 4 Simple questions are asked from the accused to establish the norms for the person's signal Like what are the normal range if these questions were asked etc.
These questions may be like so:
- What is Your Name?
- Are You from Jalandhar?
- Are You a teacher in LPU?
The main questions will be started asking after this simple questioning process ends up. Which are relating to the main case which may be like so:
- Do you know Neha?
- Did you take her to forest for committing rape?
- Are the Injuries on her body are caused by you during rape?
So during the answering of these questioning, if such circumstances arose, probability is that the person is telling a lie. If there is any fluctuation in the above mentioned factors like pulse, blood pressure etc. in the graph, the examiner may get to know the probability of any lie-detection.
Three Stages of Polygraph Test
Mainly there are three stages2 of Polygraph test in the process of lie-
detection let's discuss about them so the stages are as following:
2 There are three stages in this process of Test:
In-Test Stage Post Phase Test
This is the first stage in which the person who is undergoing
this test, is well informed about the specific issues , that is going to be
Examiner also tells the accused that he has a constitutional right3 to not to
take this test , if he don't want to take this test he may refuse and will not
be compelled for the same.
Examiner also tells about the necessary documentation , which is required for
conducting this test.
Examiner also tells about the equipment, machine etc. how they work in testing
and along with that he tells about the principles and different components of
Lastly, Examiner can tell him that if accused has any query he can ask.
- In-Test Stage-This is the second stage of the test.
This is the stage when a person is
about to undergo the test. So before he go for taking test, The Examiner puts
some painless components around the body of accused person, so there are
three basic components like:
- BP CUFF - This is secured Around the Upper Hands, Arms of the accused and
the purpose of obtaining Continuous tracing of his cardiovascular45 activity.
- No person shall be compelled to be a witness against him.
- The cardiovascular system refers to the heart, blood vessels and the
- The main function of the cardiovascular system is therefore to maintain
blood flow to all parts of the body, to allow it to survive. Veins deliver
used blood from the body back to the heart.
Convoluted Rubber Tube- This rubber is put around the chest of accused and
abnormal area to know about the respiratory system of him.
Electrodes- These electrodes with an insulated seeding known as Galvanometer6 ,
that are attached to the tips of the fingers for the purpose of tracing
activities .as u can see in the image I have put below side. Also known as pneumograph.
After this equipment system is well settled, the in test Stage is started- There
is a examination of the polygraph test, once the examinee is under, the examiner
is going to ask many questions from him.
There are three tests of The accused. Each test is asked for five minutes only.
Maximum there can be 6 tests can be performed in this process. Two minutes
Relaxing Time is given between each test.
- Post Phase Test- This is the last stage of the test:
In which Examiner tell the results to the accused. Graph will also be shown to
For example, if there was any fluctuations, then accused with get chance to
speak on his part.
At the end, the report containing evaluation of obtained result with
interpretation and his professional opinions, is given.
After Examining, The Examiner Evaluate the results of the graph obtained.
Generally, there are three forms of results which are as following:
Sr. No Form of Results Meaning of results
- NDI No Deception Indicated
- DI Deception Indicated
- INc. Inconclusive
If NDI Occurred , then it means no any abnormal fluctuation found or the person
is telling the truth.
If DI Occurred, then it means there were abnormal fluctuations in the graph ,
hence the person is not telling the truth.
If INc. Occurred, that means Examiner was not able to conclude the proper
Evidentiary Value Of The Test
On 2010, Supreme court gave verdict that:
Direct evidence from polygraph interrogation is inadmissible unless supported by other evidence.7
- Involuntary interrogation amounts to 3rd degree methods and the court cannot permit such tests.
- The material and other evidence derived from the polygraph interrogation can be used as evidence under the Section 27 of the Indian Evidence Act.
After some time later, National Human Rights Council gave some guidelines w.r.t. this test for protection of human rights, said that-
- Test will be done only on the consent of accused8
- He should be given access to a lawyer and the physical, emotional, and legal implications of such a test should be explained to him by the police and his lawyer.
- Admissible with supportive documents only.
- State of Bombay v. Kathi kalu Oghad,
So we can say that, it's admissible ,but not completely , there are many
restrictions upon it.
Application Of Test In Many Cases:
Partibha Shrikanth Rape case
.-In Bangalore, , a woman employee of BPO was raped
and murdered. The charge was framed on a driver hired by the company. The driver
was subjected to polygraph test, brain mapping test, and narco analysis test.and
it was successful.
Shivani Bhatnagar murder case.-The Indian Express Journalist Shivani Bhatnagar
was murdered at her East Delhi apartment on 23rd January, 1999. In this case
murder charge was framed on a Haryana Cadre I.G. Police Mr. R.K. Sharma and.
five other accused persons. The polygraph tests were conducted on Shivani's
husband, her sister, brothers and brother-in-law.and it was successful too.
Nithari's serial killing accused.- In Nithari, Noida (U.P.), a businessman
Mohinder Singh Pandher and his domestic help Surinder Koli were accused of
murdering 30 missing children. In this case the investigating agencies used
polygraph, brain mapping and microanalysis tests on both of them and also on a
female servant who allegedly lured children who were killed by both.
Mumbai serial killer.-One Ravindra Kantrole, a suspect of serial killing of
seven people in South Mumbai in Marine Drive and Azad Maidan Police Station, was
subjected to scientific tests like polygraph, narco analysis and higher version
of brain mapping tests . During these tests he confessed his involvement in the
crimes. BEOS (brain mapping) and polygraph tests were conducted at Maharashtra
Forensic Science Laboratory, and narco analysis tests were conducted at
Bangalore Forensic Science Laboratory on 14th February, 2007.
Apart from these, there are so many other cases which helped the police and
investigators to find the suspect, although this test is not properly admissible
in the court of law , but it helps logically in sorting out many issues.
Conclusion & Suggestions
Such type of tests like polygraph test has faced a number of criticisms and it
is still unclear to Until when they would get a full prove recognition in India.
The manner in which modern-day criminals make use of science and technology in
committing the criminal activities has compelled rethinking on the part of the
criminal justice establishment to seek the help of the scientific community to
come to the help of the police, prosecutors and the courts.
One negative approach is that, it somewhat violates constitutional provisions of
a person iss compelled to give evidence against himself. but on other hand also
useful for the investigators, police etc.
- The judiciary will order compulsorily to conduct these tests for rape
- Judiciary will impose strict restrictions to conduct these tests in a
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