The Central Bureau of Investigation (CBI) has secured permission to administer a polygraph test to Sanjay Roy, the prime suspect in the harrowing rape and murder of a 31-year-old postgraduate trainee doctor at Kolkata’s RG Kar Medical College and Hospital. This gruesome incident occurred earlier this month, sending shockwaves through the city. The decision to conduct a polygraph test on Roy is a significant development in the ongoing investigation.
But what exactly is a polygraph test, and how can it contribute to solving a crime? Commonly known as a lie detector test, a polygraph test measures and records various physiological indicators, such as blood pressure, pulse, respiration, and skin conductivity, while the individual is being questioned. The underlying principle of this test is that changes in these physiological responses, like an increased heartbeat, rapid breathing, or excessive sweating, are often associated with deception. The theory suggests that when a person is lying, their body reacts differently than when they are telling the truth.
These physiological reactions are measured using instruments like blood pressure cuffs, sensitive electrodes, and pneumographs. The data collected from these instruments is then analyzed to determine whether the individual’s answers are truthful, deceptive, or uncertain.
However, the accuracy of polygraph tests remains a subject of considerable debate. While these tests are sometimes employed in criminal investigations and for employment screening in several countries, scientific evidence does not conclusively support their 100% accuracy. The American Psychological Association highlights that there is no definitive proof of a unique physiological pattern associated with deception. An honest person could become nervous while answering truthfully, while a dishonest person might remain calm and composed. Moreover, robust scientific studies validating the reliability of polygraph tests for detecting deception are limited.
Despite these concerns, probing agencies often seek court permission to utilize polygraph tests as a ‘softer alternative’ to more forceful interrogation techniques in an attempt to extract the truth. The use of polygraph tests in this case underscores the efforts being made by the CBI to unravel the details of this horrific crime and bring the perpetrator to justice.
