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Source- This post on Polygraph test has been created based on the article “Kolkata doctor rape-murder: What Sanjay Roy told CBI during polygraph test” published in “Hindustan Times” on 27th August 2024.
Why in News?
Recently, the main accused in the rape and murder of a trainee doctor in Kolkata’s RG Kar Medical College and Hospital Sanjay Roy was subjected to the polygraph test, days after he claimed innocence in the rape and murder case.
About polygraph test
| Aspects | Description |
| What is it? | A polygraph test is a method used to measure physiological responses to questions to determine whether a person is being truthful. |
| What it records? | The polygraph device records several physiological indicators such as heart rate, blood pressure, respiration, and skin conductivity (sweating), which can change when a person is under stress or lying. |
| How the Polygraph Test Works? | 1. Preparation: Before the test begins, the examiner explains the procedure to the subject and asks baseline questions to establish normal physiological responses. 2. Testing Phase: The examiner asks a series of questions both relevant (related to the matter under investigation) and control questions (unrelated to the specific issue). The polygraph measures and records the subject’s physiological responses to each question. 3. Analysis: The examiner analyses the recorded data to identify any significant physiological changes that may suggest deception. If the subject’s physiological responses differ markedly when answering relevant questions compared to control questions, it might indicate that the subject is being deceptive. |
| Uses of Polygraph Tests | 1. Law Enforcement: Polygraph tests are commonly used in criminal investigations to help assess the credibility of suspects or witnesses. 2. Employment Screening: In some countries and for specific jobs, particularly in security-sensitive areas such as law enforcement or intelligence agencies, polygraph tests are used to screen potential employees. 3. National Security: Governments sometimes use polygraphs to monitor and evaluate individuals with access to classified information. |
| Limitations and Controversies | 1. Accuracy and Reliability: The accuracy of polygraph tests is debated due to potential influences like the subject’s psychological state, examiner bias, and external pressures. Some may also manipulate their physiological responses to “beat” the test. 2. Legal and Ethical Issues: Many jurisdictions do not accept polygraph results in court due to reliability concerns. There are also ethical issues, particularly in employment, where polygraphs may invade privacy and lead to discrimination. 3. False Positives/Negatives: Polygraphs can produce false positives (detecting deception in truthful individuals) and false negatives (indicating truthfulness in deceptive individuals). |
Legal Provision related to it
1. Article 20(3) of the Constitution protects an accused person’s right against self-incrimination, allowing them to refuse to undergo any tests like the polygraph.Any confessions obtained from such tests are not admissible as evidence in court.
2. However, any discoveries or leads obtained as a result of information revealed during these tests can be admitted as evidence, as established by the Supreme Court in the 2010 judgment in Selvi & Ors vs State of Karnataka & Anr.
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