Section 68 of The Bharatiya Sakshya Adhiniyam :Proof where no attesting witness found.
Proof where no attesting witness found. The Bharatiya Sakshya Adhiniyam 2023
If no such attesting witness can be found, it must be proved that the attestation of one attesting witness at least is in his handwriting, and that the signature of the person executing the document is in the handwriting of that person