Dear Rich: I want to write a screenplay about a real life person. This person is deceased and has been the subject of several non-fiction books as well as magazine and news articles. My screenplay would not be directly based on a particular work but would be an original conception using incidents from the subject's life. The real name would be used, though. I was wondering if I could write my screenplay on spec and what, if any, copyright or life right issues I may have to deal with? Write on! A deceased person has no privacy rights and can't be defamed, so you're free to write what you want. However, the same would not be true about those still living. For living folks, you can avoid defamation claims by dealing in the facts, which are free for all to use. Also, you should avoid copying more than the facts from any published nonfiction works about the person. By the way, we explored life rights from another angle in a previous entry.
If the person is deceased and real names are not used ... In that case, you've shielded yourself from most potential liability -- as did Harold Robbins when he wrote The Carpetbaggers, based on the life of Howard Hughes (though some sources unconvincingly claimed it was based on Bill Lear, designer of the Lear Jet).