In a 10-month-long dispute between the Conan Doyle Estate and writer/editor Leslie Klinger, the trial court ruled 50 of the Sherlock Holmes stories, all published prior to 1923, are in the public domain. Ten stories published after 1923 are protected by copyright in the US.
The court held elements introduced in the Sherlock Holmes stories published after 1923, such as Watson having a second wife, remain under copyright in the United States.
The UK copyright for all the Sherlock Holmes stories expired in 1980. According to UK law, the term of copyright protection is the life of the author plus 50 years. Mr. Doyle died in 1930.
Even though the works were originally published in England, they still receive copyright protection in other countries. The protection in the US, is based solely on US law. So why is 1923 the magic year in the US, the short answer is with implementation of the Copyright Term Extension Act it was determined that works published prior to 1923 are in the public domain. “Because of legislation passed in 1998, no new works will fall into the public domain until 2019, when works published in 1923 will expire. In 2020, works published in 1924 will expire, and so on.”