What is polygraph test that CBI will conduct on Kolkata murder-rape accused Sanjoy Roy?

Sanjoy Roy is accused of committing the crime against a 31-year-old second-year trainee doctor at RG Kar Medical College and Hospital.

The Central Bureau of Investigation (CBI) has been allowed to conduct a polygraph test on Sanjoy Roy, the primary suspect in the alleged rape and murder of a trainee doctor at a Kolkata hospital.

This development has led the high court to delay the next hearing of the case until August 29.
The decision to conduct the test comes as the CBI awaits a final ruling from the special court in Kolkata.

Roy, (33) is accused of committing the crime against a 31-year-old second-year trainee doctor at RG Kar Medical College and Hospital. CCTV footage reportedly showed Roy entering the emergency building at 4 am on the day of the incident, wearing a Bluetooth device. When he left 40 minutes later, the device was missing. Later it was found near the victim’s body. The police paired it with Roy's cellphone and thus linked him to the crime.

 What is a polygraph test?

A polygraph test popularly known as a lie detector test is conducted by using a machine that measures a person’s physiological responses when they respond to questions. According to the American Psychological Association, the purpose of the test is usually to prove whether or not a person committed a crime. The test cannot test for honesty, however. Instead, it relies on the polygraph operator’s analysis of the tested person’s responses. The effectiveness and accuracy of lie detector tests are subjects of ongoing debate. According to reports, the first such test is said have been conducted in the 19th century by the Italian criminologist Cesare Lombroso. He used a machine to measure changes in the blood pressure of criminal suspects during interrogation.

How is the test conducted?

This machine monitors various physiological responses, including heart rate variations such as breathing changes, sweating when questioned, blood pressure fluctuations, pulse rate and blood flow. Instruments such as cardio-cuffs or sensitive electrodes are attached to the person.  A numerical value is also assigned to each response to conclude whether the person is telling the truth, is deceiving, or is uncertain.

How can the test help Kolkata murder-rape case?

The polygraph test, or lie detector test, can play a crucial role in the investigation.  It can be used to verify the consistency of Roy's statements and alibis.  The test measures physiological responses such as changes in heart rate, blood pressure and respiration. In that case, variations from baseline levels when answering questions can indicate potential deception. If Roy's responses suggest he may be lying, the police can concentrate on other aspects of the case or pursue additional lines of questioning. While the results of a polygraph test are not always admissible in court, they can still provide valuable information for investigators and give them a direction.

Alongside the polygraph test, psychological evaluations are being conducted on Roy and other detainees.