Holmes and Watson
Holmes and Watson in the popular BBC versionBBC

The TV world's favourite sociopathic detective has survived falling from a building, a deadly drug habit and the attentions of the fiendish Moriarty. Now he is to become truly immortal. And ubiquitous.

A court has ruled that Sherlock Holmes can be cloned by anyone who wants to do so and there's nothing the estate of his creator, Sir Arthur Conan Doyle, can do about it.

A judge in Chicago has deduced that although some of the plotlines created by Conan Doyle are still protected by copyright, the fictional detective himself is not. Los Angeles-based lawyer and author Leslie Klinger filed a lawsuit against the estate of Conan Doyle when the latter sought a fee in return for his using the fictional detective in his stories.

Klinger argued that although some of the Holmes plotlines are still protected by copyright, the characters are so widely known that writers should be able to use them freely and Judge Ruben Castillo agreed, ruling that only 10 Holmes stories can remain protected under US law.

In the United States, copyright exists for works of fiction for the life of the author plus 70 years, or 95 years after publication, whichever is earliest. Conan Doyle died in 1930 and continued publishing short stories until shortly before his death.

Castillo explained: "It is a bedrock principle of copyright that 'once work enters the public domain it cannot be appropriated as private intellectual property', and even the most creative of legal theories cannot trump this tenet."

The ruling may be bad news for the author's estate, who plan to appeal, but will be good news for fans of Sherlock, providing they are comfortable with some of the more off-the-wall ideas in the pipeline.

In China, where Benedict Cumberbatch's Holmes ("Curly Fu") is particularly popular, a replica of Victorian London is under construction outside Shanghai, ahead of a Sherlock movie masterminded by the head of the China Film Group Han Sanping. In the Chinese version Holmes – or "Peanut" – becomes a ladies' man, perhaps disappointing those who believe the two men are lovers.

Meanwhile in India a Punjabi version has been mooted, and several new Sherlock movies are planned in the US, where Robert Downey Jr has already starred in two popular films. There are even plans for a vampire movie linked with the Twilight franchise owned by the Summit studio.

All evidence that Sherlock will never lose his appeal – or, for the more cynical, that film studios are unable to come up with anything original.