Sherlock Holmes' status as a copyrighted character is easily as complicated as any of the cases he's had to solve. Created over 125 years ago, Holmes would remain a fixture in author Arthur Conan Doyle's work until the late 1920s. In the UK, that means that all Sherlock Holmes stories are in the public domain, where they can be used and adapted by other authors. But under American law, ten stories remain copyrighted, and Conan Doyle's estate has argued that this is enough to keep Holmes and Watson under their jurisdiction. Earlier this week, though, a lawsuit changed that, as Judge Ruben Castillo found that the two characters were no longer protected by copyright in the US.

Castillo was responding to a case against the Conan Doyle estate by lawyer and Holmes scholar Leslie Klinger, who has edited collections of newly written Sherlock Holmes stories. When one author included a character from a copyrighted story in an anthology, the estate insisted that the publisher license not only that character but Holmes and Watson as well, suggesting it would work with retailers to pull the book off shelves. Klinger went to court to defend the anthology, and Castillo determined that any characters and story elements from before 1923 — the cutoff date for the copyrighted stories — were fair game for other authors. The ten later stories, Castillo wrote in his opinion, built on the characters of Holmes and Watson, but only the incremental changes they introduced could be protected by copyright.

Effectively, this means that anybody can write about Sherlock Holmes, but they might have to leave out some details that were added in later stories: one couldn't mention, for example, Watson's past as an athlete or Holmes' retirement from his detective agency. Ruben also denied part of Klinger's request, saying that the anthology included examples of things that clearly weren't in the public domain, like characters written later in the series. But he flatly denied the Conan Doyle estate's major argument: that Holmes and Watson were such well-rounded, three-dimensional characters that they continued to develop throughout the series. Klinger "suggests that Holmes and Watson can be dismantled into partial versions of themselves," wrote the estate in an earlier defense. "But a complex literary personality can no more be unraveled without disintegration than a human personality."

Ruben said that, from a legal perspective, that's exactly what can be done, especially because judging literary quality is difficult to do in court. "Conan Doyle fails to offer a bright line rule or workable legal standard for determining when characters are sufficiently developed to warrant copyright protection through an entire series," he wrote. Of course, the legal situation up until now hasn't necessarily dampened the supply of Holmes adaptations. In addition to countless film, television, and video game versions of individual stories, there are two modern-day reworkings on the air: the American Elementary and Steven Moffat and Mark Gatiss' Sherlock, which in turn has a large community of fan fiction writers. The final ten Holmes stories, meanwhile, won't be in the American public domain until the 2020s.