Polygraph And Narco Tests
1. What is a Polygraph Test?
A polygraph test measures physiological indicators such as blood pressure, pulse, respiration, and skin conductivity while the subject answers questions.
The underlying assumption is that deceptive answers produce distinctive physiological responses.
Commonly referred to as a lie detector test.
Used mainly during investigations to assess the veracity of statements.
2. What is a Narco Test?
Also called narcoanalysis or "truth serum" test.
Involves administering drugs (usually sodium pentothal) to induce a hypnotic or semi-conscious state where the subject is believed to be less capable of deception.
The subject is questioned, and the answers are recorded.
Used to extract information or verify statements during investigation.
3. Legal Status of Polygraph and Narco Tests in India
Neither polygraph tests nor narcoanalysis are considered substantive evidence under Indian law.
These tests are voluntary; if a person refuses to undergo them, it cannot be compelled.
Results are not admissible as evidence under the Indian Evidence Act but may be used as an investigative tool.
The Supreme Court has clarified their use within the framework of Article 20(3) of the Constitution (right against self-incrimination).
Key Case Laws on Polygraph and Narco Tests
1. Selvi & Ors. v. State of Karnataka (2010) 7 SCC 263
Facts:
The Supreme Court examined the constitutional validity of narcoanalysis, polygraph, and brain-mapping tests.
Petitioners challenged these tests as a violation of the right against self-incrimination (Article 20(3)).
Judgment:
The Supreme Court held that these tests can only be conducted with the informed consent of the accused.
The results of these tests cannot be admitted as evidence in court.
If the accused refuses to undergo the test, such refusal cannot be held against them.
The tests are permissible only as investigative tools, not as a substitute for evidence.
The Court emphasized protection against forced administration to protect personal liberty and privacy.
Importance:
Landmark judgment safeguarding fundamental rights.
Clarified that involuntary administration of such tests violates constitutional rights.
2. Raghuraj Singh v. State of Bihar (2001) 2 SCC 398
Facts:
The accused was subjected to a narco test during investigation.
The trial court admitted the narco test report as evidence against the accused.
Judgment:
The Supreme Court held that the narco test report is not admissible as evidence.
It can only be used for investigation, not prosecution.
The court reiterated the voluntary nature of such tests.
3. State of Maharashtra v. Dr. Praful B. Desai (2003) 4 SCC 601
Facts:
The Supreme Court dealt with the question of medical negligence in performing narcoanalysis tests.
The accused was administered the test forcibly, and questions were raised regarding legality.
Judgment:
The court reiterated that the test cannot be forced.
Emphasized that fundamental rights and medical ethics must be observed.
Use of such tests without consent violates personal liberty.
4. Nandini Satpathy v. P.L. Dani (1978) 2 SCC 424
Facts:
Though not directly related to polygraph or narco tests, this case is important for right against self-incrimination.
The Court held that a person cannot be compelled to answer questions that might incriminate themselves.
Relevance:
Forms the constitutional basis for refusing polygraph or narco tests involuntarily.
5. Selvi v. State of Karnataka (2012) – Follow-up on Selvi Case
Facts:
Post the 2010 judgment, the police conducted narcoanalysis on the accused without full consent.
The accused moved court challenging the procedure.
Judgment:
The Supreme Court reaffirmed the earlier judgment.
Any evidence obtained through coercion or without informed consent is invalid.
The test results do not amount to evidence but can guide investigation.
Other Important Points
Voluntary consent is key: Police cannot compel a suspect to undergo these tests.
Refusal cannot be treated as an admission of guilt.
The Indian Evidence Act does not list these tests as reliable evidence.
Courts usually reject such test results in the absence of corroborative evidence.
These tests may sometimes lead to false positives or false negatives, hence their unreliability as standalone evidence.
Summary Table of Admissibility
| Test Type | Voluntary / Mandatory | Admissible as Evidence? | Use |
|---|---|---|---|
| Polygraph Test | Voluntary | No | Investigative tool |
| Narcoanalysis Test | Voluntary | No | Investigative tool |
Conclusion
While polygraph and narco tests can assist police in investigations, the Indian judiciary has clearly restricted their use to investigative purposes only and protected the accused's constitutional rights against forced administration and self-incrimination.
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