The test was conducted at the Forensic Science Laboratory (FSL) in Gandhinagar.
"Narayan Sai was taken to the FSL where he willingly underwent voice spectrography test," said DCP (Crime), Surat, Shobha Bhutada.
The spectrographic voice identification test entails recording of sample voice of the concerned person (accused) and matching it with the voice which is already recorded or taped. The wavelengths and frequency of both the voices are studied thoroughly and analysed.
Sai, accused of repeatedly raping a young woman inmate of Surat ashram between 2002 and 2005, is in police remand till January 1 for allegedly hatching a conspiracy to offer bribe to policemen and even judicial officers to make the case less stringent. Six persons, including a police sub-inspector, were arrested earlier this month, in this connection.
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Two sisters from Surat had lodged separate complaints against Sai and Asaram, accusing them of rape and illegal confinement, among other charges.
Sai was booked under various IPC sections of rape, unnatural sex, molestation, wrongful confinement, unlawful assembly, rioting and criminal intimidation on the complaint of the younger sister.
Asaram (72) is currently lodged in a Rajasthan jail in connection with alleged sexual assault of a minor girl at his ashram in Jodhpur.