Under RTI Act 2005 you can seek information as it is, in the concerned office. So frame your questions to get the copies of the information in such a manner, that they have to furnish information that will serve your purpose. You can also seek information about the file notings etc. Keep your questions simple, straight and to the point so that they do not get excuses to deny or delay the information. You may also ask for personally reading of the concerned files. Once you are able to narrow down to the information of your interest and purpose, you can get a copy of that information. If you want to take somebody else along with you to help physical inspection of files, you may also do the same since the information furnished under RTI is public information.
File a RTI application with the fees and when the SDM office give you the information then collect other relevant evidence and if you think that you are right then file a compqalint against SDM or any other official to higher authorities or file a Public Interest Litigation/feel free to contact any time me on 9953809956 or write me on firstname.lastname@example.org