New Delhi, (The Telegraph): Salwinder Singh, the police officer who was allegedly abducted by the Pathankot airbase attackers, appears to have given several "deceptive answers" in a lie-detector test, according to a preliminary report.

An official of the National Investigation Agency (NIA), which is probing the attack, told The Telegraph: "According to the preliminary finding of the lie-detector test, he gave deceptive response to some of the questions. We are waiting for the final report from the analysts."

Singh underwent the polygraph test for two days, conducted by officials of the Central Forensic Science Laboratory (CFSL) in Delhi.

When this newspaper tried to contact Singh for his response, it was found that his phone had been switched off.

However, an official said Singh had informed the NIA that he was under medication when he took the test, following which the agency might subject him to another polygraph test.

The agency today searched Singh's houses in Gurdaspur and Amritsar and also the residences of his cook Madan Gopal and jeweller friend Rajesh Verma in Pathankot.

A search was also carried out at the home of a woman said to be known to the SP-rank Punjab police officer.

NIA director Sharad Kumar said: "The search got over tonight and the probe is going in the right direction. We are waiting for the final polygraph test report."

Singh, a Punjab police officer, had earlier said the terrorists had hijacked his vehicle with a blue beacon on the night of December 31, a day before the attack inside the airbase, and kidnapped the occupants: Singh, Verma and Gopal. Apparently, the officer and the cook - and later the jeweller - were thrown out of the vehicle that was found abandoned less than a kilometre from the air force station.

The investigators are also probing whether the drug mafia, which have struck deep roots in Punjab, helped the attackers.

NIA officials said the questions that elicited "deceptive answers" from Singh included the following:

♦ Why he planned to go to the shrine (around 150km from Pathankot) in the middle of the night on December 31 despite a security alert.

♦ Why he did not carry his revolver and take his gunman along.

♦ Why he took the cook and his friend along rather than the security guard.

♦ Why the blue beacon on the car was switched off.

♦ Whether he had planned a New Year's Eve party on that night and was waiting to meet someone when the terrorists surfaced.

♦ Why he went to Bangkok twice in the past one-and-a-half years.

A person taking the polygraph test is made to sit on a chair, and three physical reactions - the heart rate, blood pressure and sweat - are monitored using electrodes attached to the fingers, according to a CFSL official.

"We ask both neutral and critical questions and analyse the patterns to determine whether the person is truthfully answering questions or lying. This is done by analysing the person's respiratory rate, cardiovascular activity and sweat gland," the official said.

The test is conducted on the assumption that a suspect will show involuntary responses to critical questions.

However, the polygraph test is not always foolproof. "Fear, anxiety or worry can also trigger psychological responses in a person's body that could make him or her appear to be lying," another analyst said.

Criminal lawyer M.S. Khan said a polygraph test result was not substantive evidence and could not be used to prove guilt. "It is not an admissible piece of evidence in court as the test is not foolproof. But it can be used for corroboration of other evidence found against the accused," he said.

Photo credit: The Telegraph