Siya Goyal, accused in the murder of her fiancé and realtor Ketan Agarwal, has agreed to undergo a polygraph test, commonly known as a lie detector test.
A polygraph test measures physiological responses such as blood pressure, pulse, respiration and perspiration while the subject answers questions pertaining to the incident.
An application was filed before the Vadgaon Maval Court seeking permission to conduct polygraph tests on Goyal and the co-accused, Chetan Chaudhary. The test requires the consent of the accused as well as the permission of the court.
Siya's lawyer confirmed that his client has agreed to undergo the test. Earlier in the day, the lawyer was quoted as saying, "The police moving this application for a polygraph test shows that they do not have concrete evidence in the case and are even fumbling for leads."
While the results of the test are not admissible as substantive evidence in the court, they may help investigators piece together the case and could also lead to the discovery of evidence that is admissible in court.
The test is considered important because there are no eyewitnesses or CCTV footage to corroborate the alleged murder. According to the police, the two accused had also destroyed evidence, which included extensive call records. Police believe that the lie detector test could help verify the statements of the accused and possibly generate fresh evidence.
Meanwhile, on Thursday morning, police took Siya to a location in Pune where she and Chaudhary had allegedly rehearsed pushing Agarwal off a cliff at Lohagad Fort.
The alleged rehearsal took place in May, and the probe is on to find out the exact date and other details, a police official said.
"We have also collected a substantial amount of technical and digital data, which is currently being analysed and cross-verified," he added.
What does the Indian Journal of Medical Research say about polygraphs?
According to the IJMR, the underlying theory is that a guilty person is more likely to experience heightened stress while lying about facts related to a crime. This "produces a hyper-arousal state" that can be interpreted by a trained examiner analysing the polygraph results.
The test measures physiological responses such as heart rate, blood pressure, respiratory rate, skin conductance and electromyography to identify signs of this hyper-arousal.
However, the scientific basis of the test remains contested. The IJMR states that "the measured changes in arousal state are not necessarily triggered by lying or deception."
Instead, similar physiological responses can result from nervousness, anxiety, fear, confusion, hypoglycaemia, psychosis, depression, the use of substances such as nicotine or stimulants, alcohol withdrawal, or other emotional states.
It also points out that the subject's physiological responses may be influenced by the manner in which questions are asked by investigating officers.
According to the IJMR, "it is not difficult to beat polygraph tests by a trained person," who may be able to control or suppress physiological responses through relaxation techniques, yoga or meditation.
As a result, "the reliability of the polygraph test has been repeatedly questioned in empirical studies."
