Hi
In general, if documents pertaining to properties of relatives are seized during ACB raids, and the relatives are not mentioned either in the FIR or in the charge sheet, courts will ask ACB to handover the documents to the respective owners.
In general if the petitions are filed under sections 451 and 457 of Cr.P.C., and Sections 4 and 8 of the P.C Act, Courts will order release of documents if
a) Properties of your father in law are obtained by your father in law's own source of income and the same is demonstrated by providing income tax returns and other sources of money
and
b) your father in law is not a party to the said case
And/OR
c) If the IO also is in favour of granting no objection to release of documents.
Since a counter has been filed by IO, in all likelihood, there might be some resistance from IO to grant No objection for release of title deeds.
So your lawyer should make a prima facie case on
a) The property acquired through own sources of income by your father in law.
b) No offence registered against your father in law.
c) No co-relation(direct/in direct) between the alleged offence and your father in law, except that your father in law is a distant relative
So if your lawyer can argue on the above points, in all likelihood, on 11 may , your father will get the relief as prayed for by him.
Hope this information is useful.