Polygraph Test

Context (TH): The Central Bureau of Investigation (CBI) conducted polygraph tests as part of the investigation into the Kolkata doctor rape-murder case.

• Definition and Function: A polygraph, commonly known as a lie detector test, is a device or procedure that monitors and records physiological responses such as blood pressure, pulse, respiration, and skin conductivity while a person answers a series of questions.
• Underlying Principle: The test operates on the premise that physiological reactions differ when a person lies compared to when they tell the truth.
• Accuracy and Reliability: Polygraph tests are not entirely reliable, as the results depend heavily on the interpretation and assumptions of the polygraph examiner.
• Legal Status in India: According to the Indian Evidence Act of 1872, the results of a polygraph test are not regarded as conclusive evidence but can be used to corroborate other pieces of evidence.
• NHRC Guidelines: The National Human Rights Commission (NHRC) mandates that polygraph tests require the voluntary, informed, and documented consent of the accused, along with proper documentation of the process.
• Judicial Consideration: Statements made during polygraph tests are not treated as confessions. Judges must consider various factors, including the duration of detention and the methods used during interrogation when evaluating the results.
• Legal Precedent: In the Selvi vs. State of Karnataka case (2010), the Supreme Court ruled that involuntary narco-analysis or polygraph tests violate an individual’s mental privacy and the right against self-incrimination as guaranteed by Article 20(3) of the Indian Constitution.
  • Article 20(3): This article states, “No person accused of any offence shall be compelled to be a witness against himself.”

Narco-Analysis

• Definition: Narco-analysis involves administering drugs such as sodium pentothal, scopolamine, or sodium amytal intravenously to place the subject in a semi-conscious state, with the aim of extracting information.
• Legal Considerations: While statements made under narco-analysis are not admissible as direct evidence, any physical evidence discovered based on voluntary test results may be considered admissible under the Indian Evidence Act of 1872.

Brain Mapping

• Definition: Brain mapping involves analyzing brain activity recorded by electrodes placed on the scalp to detect the presence of “guilty knowledge” in the subject.
• Legal Status: The results of brain mapping tests do not have legal validity in court but may assist in the investigative process.