A planned Netflix movie about Sherlock Holmes’s sister is the target of a lawsuit from the estate of Arthur Conan Doyle, the creator of the legendary detective. The estate has asserted both copyright and trademark claims.

The estate will have to walk a narrow path to prevail on its copyright claims. All but the last ten Sherlock Holmes stories have fallen into the public domain.  A 2014 Federal Circuit Court decision ruled that the attributes of the character had done so as well. The estate’s claim is that those ten stories still under copyright include “significant new character traits” that Netflix is using in its “Enola Holmes” spinoff. It cites as one example the “warm friendship” between Sherlock Holmes and Dr. Watson that it says was portrayed for the first time in the final Holmes stories.

The complaint also raises trademark claims. From the estate’s standpoint, a trademark has the benefit of never expiring as long as it remains in use. In order to prevail on this claim, the Conan Doyle estate will need to make the typical factual showings for trademark infringement: that the Holmes character signifies a source or origin of goods or services and that the Netflix movie would be likely to cause consumers to be confused as to its source or origin.

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