I want to use information posted on Facebook as the basis for a TV script. Its someone I'm friends with. I also want to use the persons First name and details about their life. I have known this person for a long time and its potentially a great story, however because its about the persons train wreck of a life and the battle with personal & professional problems they will not like it.
Its far too early to offer the person a EP credit but i wonder how do I stand legally ? Does information shared on Facebook constitute public domain ?
Where in the U.S. are you located, sm70911, or, if not in the U.S., what country do you live in? Laws vary from state to state and laws vary in significant ways between countries.
You can use what you find publicly posted on the internet as the basis for a TV script. You can take the ideas you find and use them in your own creative way. However, you cannot base your script on someone else's life if the person upon whom you base your script is identified or identifiable, without risk of a lawsuit, unless you have that person's express permission (in writing) to do so.
The lawsuit could potentially be for invasion of privacy/misappropriation of a name or likeness, or the lawsuit could be for invasion of privacy/publication of private facts (if you are "friends" on Facebook but the friend has limited access to his/her page), or the lawsuit could be for invasion of privacy/false light (depending on how you present the story), or the lawsuit could be for defamation (depending on the contents of the script), or the lawsuit could be for all of the above and more.
Most publishers (and this includes broadcast publishers) will not accept unsolicited scripts, for one thing, and publishers almost always require liability releases from anyone who is identified or identifiable as a "character" in a story. If one person can recognize the real person behind your character, you open yourself up to a costly lawsuit.
Just because something is published online, it is not (necessarily) in the "public domain" (and it generally isn't). Most of what you see online is rights-protected material. Public domain has a specific meaning under the law (e.g., material first published before 1923).
I recommend you ask your friend for permission, have your friend sign a release, and, perhaps, offer this friend compensation for the use of his/her story. And, even with the release signed, you should have your script reviewed by a publishing law professional, to make sure you have not crossed any other legal lines with your writing.