Libel is where you write something that is damaging to another person. If your writing is professionally damaging to that person, the scope for redress is even greater.
Libel is a publisher’s nightmare as it can lead to bankruptcy and the end of a career for you as a writer. Caution is the watchword when handling contentious issues which may put you at loggerheads if you have something you passionately believe in.
The main defence to libel is in writing the truth. What constitutes the “truth” may be a very difficult thing to prove once you are in a court of law and you are required to back up your claims. From bitter personal experience of courts in the UK and the US, though fortunately not for libel, I have learned to appreciate that there is a huge difference between what I know and what I can prove.
Libel is something that can affect both the non-fiction and fiction writer. Writing a denigrating piece that places a product in a bad light can be considered libellous, so product or service comparisons must be made with care. Using a fictional name for a character in a novel that you are basing upon a real life individual will not protect you from a libel suit if that person is identifiable from your writing.
It is necessary to demonstrate that you have been malicious or reckless when demonstrating libel. This is why you see disclaimers along the lines of “All characters are fictional and any relation to persons living or dead is unintentional.” but you still must take reasonable steps to ensure that you are not using someone’s name who actually exists. If you were to write about a politician or business person who is corrupt, you should Google that name and ensure no politician exists out there that has the name of your fictional character.
You cannot libel the dead so essentially you can write what you want about them. It would lead you open to criticism about making allegations against someone wh is unable to defend themselves or indeed, you may indirectly libel living relatives of the deceased. Best not to get involved in either case.
If you inadvertently libel someone, the best course of action is to consult a lawyer and your publisher. Issuing an apology and a retraction tend to do the trick but libel in the UK is serious and it can be horribly expensive so take care.