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  • Writer's pictureNeha Mohanty

Polygraph test in law

The polygraph test also known as the lie detector test is such a test or an activity

that is undertaken to find the truth and is basically experimented on the

accused, suspect, or witness when they are asked to tell the truth at times asked

by the examiner. By undergoing this test a person gets easily caught if he or she

tries to hide things and tell lie. They are also called a Deception Detection test

And they have a wide moral, legal, and social importance in society. These tests

like polygraph test, narco analysis, brain mapping, live detector test are some of

the tests which help in the investigation of a crime. By conducting the

investigators' police, lawyers easily detect the lies from the culprits. And

also increase the efficiency in the inquisition or inquiry of the crime. So from this

article, we are going to know more about the polygraph test in detail, Its

advantages and drawbacks, the methods to conduct, whether it is violative of the

fundamental rights of the accused.

First, we need to understand the method of conducting the polygraph test

in order to know whether this test can be reliable or not.


The theory which follows this test is that when a person is telling a lie or is lying

about something then his body will produce different physiological responses or

effects such as increased heart rate, blood pressure, respiratory rate, skin

conductance which is more than the normal course. And it will be noted by the

examiner while conducting the test. And there will be an instrument called

electromyography which will record the electrical activity of different parts of the


The examiner begins the test with a pre-interview session to gain some

information beforehand which can be used later on for diagnosing questions.

And then the examiner will make that person undergoing the test explain how it works and it is very important to speak the truth. Then after that, a small demo test is conducted to test whether it can detect the lie so that the person can be sure that the test can detect the lie. Then the real test start by which the examiner asks certain irreverent questions then others are diagnostic questions. And the examiner actually tests in asking the relevant questions. The different types of questions alternate and then the test is passed if the physiological responses to the diagnostic questions are larger than those of the irrelevant


Then next comes the control question technique(QCT). The examiner before

conducting this technique have informed the person regarding the validity of the

administration of the control question technique. It starts with some interrogative

questions by which it elicits a nervous response from the suspects.

An alternative to this technique is the guilty knowledge test or the concealed

information test. The examiner conducts this test with having no knowledge of

the crime . The examiner tests the suspect on the knowledge of the crime that is

not known to the innocent person. The questions are multiple questionsbased and

the participants are rated on how they react to the correct answer.


The National Human rights commission adopted certain guidelines on 12th

November relating to the administration of the Polygraph or Lie detector test as

the commission received many complaints against the test that it is being

conducted by coercion or without the consent of that person. So the commission

decided as the lie detector test is not regulated by law so they formulated certainly

guidelines thathas need to be followed. The following guidelines are:-

1) No test can be conducted without the permission of the accused. Options

should be provided to the accused to ask whether they want to undertake the

test or not and if they agree to do it voluntarily then he should be given access to

the lawyer and then the police and the lawyer should make the accused

understand the legal, physical and emotional aspects of such a test to him.

2) The consent given by the accused should be recorded before a judicial


3) During the hearing before the judge the accused should be represented by a


4) The judge or magistrate should take into consideration all the factors relating

to the length of the detention and nature of the interrogation.

5) The real recording of the accused should be done in an independent agency

such as hospital and presented in presence of a lawyer.


1) The investigating officer has to send a requisition addressed to the director, state FSL to request them to give a date for the polygraph examination. The requisition has to be forwarded by the superintendent of police or sub-divisional police officer. While sending requisition the officer has to attach all necessary documents such as FIR, statements of subjects recorded under section 161 CrPC, briefcase history, and if there is any photograph. This will make the experts understand the nature of the crime, and where, how and

when the crime was committed.

2) The investigating officer is advised to requisition of the services of polygraph division only after making a further inquiry and collecting relevant documents such as mobile call details, PM report, inquiry reports, age certificates.

3) The laboratory will communicate the date for consultation with the investigating officer. The experts after checking the facts will prepare a questionnaire and then fix the date for the polygraph test.

4) THe investigating officer has to meet the concerned expert at state FSL, for

discussion and for conducting the examination.

5) Before sending the requisition the investigating officer has to attach a

a eclaration that he has taken the consent of the subjects under article 20(3) of

the constitution as passed by the orders of the supreme court.

6) Only the list nominated will be examined on that date and time fixed by the


7) In the case of women undergoing the test a women constable is required to

accompany the suspect who will remain present during the examination.

8) All the minor accused will be accompanied by their parents /guardians

compulsory who will sign the consent form.


Polygraph testing has great significance as they have several practical applications. These tests are specifically conducted to detect the truth fullness from the accused committing a crime. They are used in crime investigation, security agency, business fields, and other organized sectors.

Crime investigation:-

It is one of the major fields in which polygraph testing is conducted to detect

crime. They offer government agencies and legal systems a very useful way to

detect crimes from the accused. Crime investigation teams afford more

complex procedures and they do more interrogation to find out the truth. They

also apply disciplinary methods to detect the truth. So therefore polygraph testing

is very valuable and important in crime investigation fields because it helps them

to ascertain the truth.

Security agencies:-

The polygraph test is also very important in security agencies as it helps the security

agencies to identify the suspected terrorists and other criminals who try to hide their identity. Polygraph testing not just only help in suspecting the criminal but also provides justice to the innocent victims in the crime who are punished in the court due to the wrong verdict. The polygraph test is very effective in crime investigation. It also does not deal with any physical pain on the crime suspects.

Industry and business sectors:-

In industries, they contribute towards enhancing effective organization. Their job

is to select candidates on the basis of their skills and experience and also promoting them honestly in the organization. But there are some candidates who in job recruitment do not provide correct information and might dishonestly possess their skills for getting selected. So in such cases, a polygraph test is very useful and it helps in detecting the truth. Another application is a polygraph test that helps in discovering employee thefts in the organization. Although there are so many organizations that try to employ their own methods of questioning the suspect thathelps still will not give correct results so the most relevant method of conducting the test is polygraph testing.

The traditional methods of gathering evidence may not always give many correct or

desired information. In some cases, the police officers use violence to extract

information from the criminals but that is not the correct way as it harms the

body of the accused, and also the accused may confess in the fear of violence

without having committed the crime. So in these situations the police officers can

use various scientific methods like polygraph test, narco analysis , brain mapping

in extracting the information and without doing any physical violence.

Disadvantages and negative impact

It may be illegal- under federal law, it states that an employer cannot use a

polygraph test until and unless there is a current investigation into an actual loss.

Only certain types of employers are allowed to undergo such tests. These include

pharmaceutical manufacturers, security service organization. When a ,polygraph

test is conducted it has to follow certain strict standards . Under this act the

information obtained during the polygraph test is strictly confidential.

Inaccurate results:

According to an American psychological assosciation, Polygraph test may produce

mixed results. It is still vulnerable to both physical and psychological countermeasures and also produces insignificant errors based upon false-negative results.

The results might not be accurate. The examination procedure for conducting a lie detector test is very lengthy and requires a subject to remain still. The lack of accuracy in these instruments is reflected in the misclassification of test subjects.

Ethical issues:

Polygraph testing tends to produce many ethical problems. Polygraph testing is

clear occupation into the personal privacy and liberties of an individual as many

accused or criminals are forced to undergo the test. In the case of industrial thefts

several workers are subjected to undergo this test which is against their wish is an

an important challenge to their personal autonomy.

Secondly explaining the results is another source of ethical violation in polygraph

testing. Since there is no relationship which is established between the

physiological responses and dishonest behavior.The test administrators interpret the results in a very biased manner without giving accurate results

which is itself unethical and unfair.

The legality of polygraph testing:-

The constitution protects the right of an individual from self-incrimination and

privacy and from unlawful search and activities. The constitution provides for a

general right to privacy and protects these rights against violation of privacy. It

has been argued in the jurisdictions that the right to privacy is surrendered or given out

when the employer can demonstrate a sufficient interest so it has been also argued that when an employer gives his permission for the polygraph testing he gives up his right to Polprivacy. Where conducting the polygraph test is voluntary there cannot be interference of privacy. The consent given by the person undergoing the test must be in writing and the person need to be informed that the testing is voluntary. There are certain condition such as only questions discussed prior to the examination has to be used and he or she has the right to be presented by an interpreter. There cannot be discrimination of threats.


Polygraph tests are conducted for detecting whether a person is lying or not. The

act of telling a lie is reflected from the person’s physiological and neurological

responses as their behavior changes if they deliberately try to hide the truth.

Polygraph test has many applications in different fields. It is a very scientific way

to detect the crime without causing any physical harm to the criminals.

Application of polygraph test is very much significant in crime investigation,

national security , employee theft. The success of polygraph testing will depend

on the ability to minimize misclassification of subjects. Sometimes there is a

problem where it declares false results which make the innocent as guilty .

The polygraph or lie detector test is a better method than the conventional method of

interrogation because in a conventional method the accused has to go through long

hours of interrogation and the policemen apply physical pressure on the accused

to confess their crimes whereas a polygraph testing is a very efficient method of

detecting a lie.

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