"The legal case of Klinger v. Conan Doyle Estate that settled the claim actually rested on an interesting issue, whether a copyright claim can persist on a character even if the works depicting that character have fallen out of copyright. The defense of the Doyle estate went something like this: sure, Arthur Conan Doyle's stories are now at least 90 years old, but other stories about Sherlock Holmes are still under copyright, therefore Sherlock Holmes is still under copyright.
Judge Richard Posner didn't buy the argument, and he ruled that Sherlock Holmes, the character, is now in the public domain."