In a startling relevation, Krishna, the compounder at Dr Rajesh Talwar's clinic who underwent a narco-analysis test in Bangalore on Thursday, said a second person was involved in the murders of the latter's daughter Aarushi and the servant Hemraj, but he was not forthcoming when questioned as to who it was.

It is believed that Aarushi and Hemraj's murders were committed by two persons and a khukri was used the teenager.

Krishna, who was subject to a narco-analysis test at the Bowring Hospital, Bengaluru, on Thursday at the instance of the Central Bureau of Investigation, also gave a clean chit to Aarushi.

The CBI is now probing the double murder, which took place over a month ago at Noida in Haryana.

CBI sources said Krishna, during the test, negatived both the theories, one that Aarushi was of a bad character, and two, she was involved in an illicit relationship with Hemraj. He also said in his narco test that Aarushi was innocent and it would be wrong to impute any slur to her character.

According to sources, it was also said that Talwar, Aarushi's father, may be innocent. The local police has accused him of the murders. However, CBI sources were not forthcoming on any further information regarding this aspect. Krishna also spoke about how, where and when the murder occurred.

CBI sources said that the investigation conducted by the UP police was shoddy and there were various aspects that were wrong. There is a lot of damage control exercise that needs to be done in this case, they added.

The CBI said they may have to conduct a second narco-analysis test on Krishna in order to get more information regarding the conspiracy and also the motive behind the murders.

While the CBI team has left Bengaluru for New Delhi, Krishna continues to remain in the city as he will be subject to more tests.

The brain mapping on Krishna is likely to take place on Friday where the same set of questions will be asked.

The procedure, which is three-fold, involves polygraph, narco-analysis and brain mapping tests in which similar questions are asked. The investigating agencies will then corroborate the statements following further investigation.

The news regarding Krishna being asked 350 questions is wrong, according to sources. Experts say that a person will have to remain in trance during the tests for nearly four hours in order to answer so many questions.

Remaining in this state for such a long period of time could prove fatal to the person and there is every chance of him slipping into coma.

Sources said a maximum of 50 to 70 questions were asked. All the questions asked to Krishna revolved round the role played by Talwar, Aarushi's character, the number of persons involved in the murder and also regarding the weapon.