Classic literary characters such as Sherlock Holmes have faced intense copyright battles, but now, another character is being claimed: Buck Rogers. With a potential film in the works, the estate of one of the character’s writers is claiming that they have a claim on the property.
The Buck Rogers copyright does seem to have lapsed, but Buck Rogers is also a trademark which has no expiry date (provided it has been defended by the mark holder) owned by the Dille Family Trust.
So a movie can’t use the character unless either they license the names, or can prove to a court’s satisfaction that the mark holder hasn’t defended their property (the latter case is why the Conan Doyle estate is considered to have lost the rights to Sherlock Holmes). A similar state exists over Edgar Rice Burroughs’s work which is protected by a number of trademarks which are very well defended.