It's Elementary, My Dear! Sherlock Holmes in public domain, reported by Leslie S. Klinger.
From Leslie S. Klinger's post: On Monday, December 23, 2013, the United States District Court for the
Northern District of Illinois ruled on our motion for summary judgment
against the Conan Doyle Estate in the case brought in my name last
February. The case challenged the Estate’s contention that Laurie R.
King and I needed to license the right for creators to pen new stories
about the literary figures of Sherlock Holmes and Doctor Watson. The
Court’s ruling states, in brief, that creators are free to use the
characters of Holmes and Watson without licensing them from the Conan
Doyle Estate. The Court cautioned that new stories about the pair can’t
use elements that appear exclusively in the ten post-1922 stories by
Conan Doyle (those that remain in copyright). However, elements from the
fifty pre-1923 stories are in the public domain.