is the GPA a registered or an unregistered document. i assume that because it is fake, it is an unregistered document. issue notice to the attorney, issue a public notice in the newspaper, in the place,. where the property is situated, wrt to cancellation of GPA, AND ALSO wrt the fraud sale, and alert the public that they should not engage in any type of transaction with those persons.
Now, you have taken the 1st step of filing a criminal complaint, Issue a notice to the person who claims himself as attorney, cancelling the GPa. or if the GPA is registered, how can it be registered without the party being present before the sub-registrar, to be questioned.
File a civil suit to set aside the sale made by the POA holder, as not binding on your client, along with IA FOR INJUNCTION, giving all the facts about the forgery.
Also issue a letter from your client, to the concerned subregistrar, with his photograph, stating your objection to any further registration, along with your phone number, along with your complaint to the police station, and FIR., and the public notice issued in the newspaper.
Proceed with the case, proving facts may take its own time. You need to wait for justice.