Ketan Agarwal murder case: How is lie detector test done? Is it legal? Are polygraph test results admissible in court? Can it be done if Siya Goyal says no? News18 explains
The Pune Rural Police are seeking court approval to conduct a polygraph or lie detector test on Siya Goyal, the prime accused in the murder of her 25-year-old realtor fiancé, Ketan Agarwal.
DIGITAL EVIDENCE DESTROYED: WHY POLICE NEED LIE DETECTOR TEST
Ketan Agarwal was allegedly pushed to his death from nearly 400-metre-deep gorge at Lohagad Fort near Pune. Police claim that Goyal and her alleged lover, Chetan Chaudhary, meticulously planned the murder to avoid her upcoming wedding.
The case heavily relies on circumstantial and technical proof due to specific investigative hurdles:
- There are no direct eyewitnesses or CCTV cameras tracking the exact spot of the crime at the fort cliff.
- Investigators revealed that the accused individuals deleted their extensive call log and even items from their phones’ recycle bins before and after June 18 in an attempt to destroy evidence.
- Conflicting narratives from family members and the suspects regarding the wedding arrangements have complicated the investigation into the alleged motive.
FRESH LEADS, NEW MATERIAL: HOW A LIE DETECTOR TEST MAY HELP
Under the Indian law, polygraph test results are not directly admissible as substantive evidence in court. However, the Pune Police are pushing for the test to extract crucial verbal admissions. They plan to use psychological cues to develop new leads, verify existing evidence, identify inconsistencies, or locate material evidence that can be independently verified.
The polygraph itself cannot establish guilt, and any information obtained during the test must be corroborated through independent evidence.
HOW A LIE DETECTOR TEST IS DONE
A polygraph test does not directly read minds or detect lies. Instead, it measures physiological indicators of stress caused by the fear of deception.
The process involves specific equipment attached to the body to track biological changes:
Pneumograph Tubes: Placed around the subject’s chest and abdomen to record breathing rate and patterns.
Blood Pressure Cuff: Wrapped around the arm to measure changes in heart rate and blood pressure.
Galvanometric Electrodes: Attached to the fingertips to evaluate sweat gland activity via skin conductivity.
The examiner reviews the case, explains how the equipment works, and discusses all questions beforehand to minimise outside anxiety. The examiner creates three types of questions — irrelevant questions, control questions about generic past misdeeds, and relevant questions directly tied to the crime. The examiner reads the questions while the sensors record bodily spikes during answers.
The examiner compares physiological responses to different categories of questions to determine whether responses to relevant questions differ significantly from baseline or control responses.
IS IT LEGAL? WHAT THE LAW SAYS
A lie detector (polygraph) test is legal in India only if the subject gives voluntary consent, but its results cannot be used as direct evidence or a confession in a court of law.
In the landmark 2010 judgment in Selvi v. State of Karnataka, the Supreme Court held that involuntary administration of polygraph, narco-analysis and brain-mapping tests is unconstitutional because it violates an individual’s right against self-incrimination under Article 20(3) and personal liberty under Article 21.
The legal framework governing polygraph tests is shaped by constitutional protections, the National Human Rights Commission (NHRC) guidelines, and Supreme Court precedent.
- Article 20(3) (Right against Self-Incrimination): The Constitution provides that no person accused of an offence can be compelled to be a witness against themselves. Compelling a person to undergo a polygraph test violates this protection.
- Article 21 (Right to Privacy & Dignity): The Supreme Court observed that forcing these tests constitutes mental torture and violates personal liberty and individual privacy.
WHAT IF SIYA GOYAL SAYS NO?
For a lie detector test to be legally conducted in India, the investigating agency must follow strict rules. The test must be voluntary and cannot be compelled by the police. The subject’s consent must be recorded before a Judicial Magistrate. The subject must have access to legal counsel before giving consent. The examination must be conducted by an authorised forensic agency or government facility in accordance with prescribed procedures.
