The mystery surrounding the Aarushi-Hemraj murder case is getting deeper with the Central Bureau of Investigation sparing no effort to crack the case.

Coverage: Aarushi Murder Case

On Sunday, the CBI subjected both Dr Rajesh and Nupur Talwar (parents of Aarushi) to a polygraph test in order to ascertain whether the statements given by the duo are corroborating or not.

The CBI, during the test conducted in New Delhi, tried to ascertain whether the statements given by both Krishna and Nupur Talwar regarding Dr Talwar's evidence are true or not.

CBI sources told rediff.com that, if need be, they may subject Dr Talwar to a narco analysis test. He may have to be brought down to Bangalore in case they decide to go ahead with the test.

Krishna's narco test adds new twists to Aarushi case

The CBI, at present, is probing on the two killer angle following the statement given by Krishna, a compounder in Dr Talwar's clinic, during his narco analysis test in Bangalore that there were two persons involved in the crime.

In this regard the CBI had picked up a person by name Rajkumar, a domestic help at the residence of Anita Durani, who the Noida police had alleged was having an affair with Dr Talwar.

Sources say the suspicion at present is on Krishna and Rajkumar, who may have killed both Aarushi and Hemraj. It is, however, felt that the duo may have committed the crime on the instructions of few other persons.

Aarushi murder may not have been honour killing

The CBI is now trying to ascertain whether Dr Talwar was the one who hatched the conspiracy.

Krishna has been remanded in police custody till June 17. He will subject to further questioning and the CBI claims that if the need be a second scientific test may be conducted on him. The CBI has already filed a case under Sections 302 (murder) 120-B (criminal conspiracy) and 201 (causing disappearance of evidence) of the Indian Penal Code.

The CBI wants to ensure that the tests conducted on all the accused are fool proof. A lie detector test on Krishna, which was first conducted at New Delhi, had failed completely. This time, they have utilized the services of Dr Malini, the forensic sciences expert from Bangalore to conduct the tests on all the accused persons at New Delhi.

Dr Malini, who has conducted over 200 scientific tests, is in New Delhi where she is assisting the CBI in conducting the scientific tests.