obtaining rights for adapting a book
 

here is my dillema... i have found a story written as a historical fiction by an author in 1976. the story itself took place in the 1500's and is true. (and in one form or another has been told in brief passages throughout the ages) the author apparently self published it in 1975 or 1976 and it wasnt reprinted. she recently died in 2002 and i have been trying to track down any living relatives to obtain the rights to this story( or at least her version of it!). it appears that she didnt marry or have children. the printer has no lead or connection to the author anymore. the story hasn't been made into a movie that i have found yet.
if this all pans out as stated here, and after i have exercised all due diligence and come up with nothing, what are my choices? i dont want to put the effort into this adaptation and lose it all if someone comes to claim it after it has hit the movie screens! (assuming it ever gets picked up of course. still need to be prepared though!)
what would constitute due diligance in this type of scenario?

any thoughts????

thank you in advance for everyones help on this matter!

Unfortunately, I can not give you legal advice, as you are not my client. It is possible that, either copyright in the work is invalid (pre-Berne works had a different set of requirements for obtaining protection), or that the copyright has expired. With so much at stake, you need to spend a couple of buck on a lawyer who can not only provide you with a definitive answer, but will also furnish a non-infringement opinion letter that will safeguard you from intentional infringement liability in the event that you are sued.

good advice (once again!) thanks paul.