Use Of Lie-Detectors Under Bnss
What is a Lie Detector Test?
A lie detector (polygraph) measures physiological responses (like blood pressure, pulse, respiration, and skin conductivity) to detect deception during questioning. However, its reliability and admissibility as evidence have been debated globally.
Legal Position in India
Polygraph tests are not admissible as conclusive evidence under the Indian Evidence Act.
They can be used as an investigative aid to help the police or investigators.
Consent of the accused is generally necessary.
Courts may consider polygraph results but only as a guiding factor, not as proof.
Key Case Law on Lie Detector Tests in India
1. Selvi & Ors. v. State of Karnataka (2010) — Supreme Court
Facts: The Court examined the admissibility of narco-analysis, brain mapping, and polygraph tests.
Judgment:
Held that such tests violate Article 20(3) (Right against self-incrimination) and Article 21 (Right to life and personal liberty) of the Constitution.
The Court ruled that these tests cannot be conducted without the consent of the accused.
Results of these tests are not admissible as evidence but may be used as leads for further investigation.
Significance: Established constitutional safeguards regarding involuntary use of lie detector tests.
2. R. Rajagopal v. State of Tamil Nadu (1994) — Supreme Court
Although primarily about privacy, this case laid the foundation for the right against self-incrimination and privacy in investigation.
Influences the approach toward polygraph tests, implying that involuntary tests violate privacy.
3. State of Maharashtra v. Dr. Praful B. Desai (2003) — Supreme Court
Dealt with expert testimony and scientific evidence.
Ruled that scientific tests, including polygraphs, can assist the court but cannot replace other forms of evidence.
Emphasized that such tests must be subject to judicial scrutiny before acceptance.
4. Shashi Kumar v. Union of India (2003) — Supreme Court
Held that consent is essential before conducting lie detector tests.
Coercive or forced polygraph tests are unconstitutional.
5. K.K. Verma v. Union of India (2013) — Delhi High Court
The Court clarified that polygraph results are not conclusive proof of guilt or innocence.
They can be used only as investigative leads.
Polygraph operators must be qualified and follow standard procedures.
6. Union of India v. Tulsiram Patel (1985) — Supreme Court
While not directly about polygraph tests, the Court discussed the principle that the prosecution must prove guilt beyond reasonable doubt.
Scientific tests are supplementary; the primary evidence is testimonial or material facts.
Relevant in evaluating the evidentiary weight of lie detector results.
7. State of Punjab v. Gurmit Singh (1996) — Supreme Court
Reinforced that involuntary confessions or evidence obtained through coercion are inadmissible.
By analogy, involuntary polygraph tests are also inadmissible.
Summary of Legal Position and Principles
| Aspect | Position in Indian Law |
|---|---|
| Admissibility | Not admissible as substantive evidence in court |
| Use | Investigative tool only, to assist police in investigation |
| Consent | Must be voluntary and informed |
| Constitutional Rights | Right against self-incrimination (Art. 20(3)) and privacy (Art. 21) |
| Reliability | Questionable; courts require corroborative evidence |
| Expertise Required | Tests must be conducted by qualified personnel |
| Voluntariness | Coercion or forced tests violate fundamental rights |
Practical Implications
Police may use polygraph tests to narrow down suspects or check consistency of statements.
Courts do not treat polygraph results as proof of guilt or innocence.
Defense lawyers often challenge polygraph evidence to protect clients’ rights.
Ongoing debates on whether to admit polygraph results with safeguards exist, but currently, Indian courts are cautious.
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