"In the EC the entire work of Sir Arthur Conan Doyle enjoys copyright protection until 31 December 2000. After that date, a number of characters created by the author will enjoy trademark protection."
There follows a paragraph on the Sonny Bono Copyright Extension Act in the US.
I am not sure how this applies to Holmes. Copyrights were extended after their expiry date, and it seems that this extension date is used as a take-off point for the Bono date of 95 years after publication- I dunno!

Andrea Plunkett controls the US copyrights to the Sherlock Holmes stories.
From the Sherlock Holmes Literary Estate:
Licensing:
In the UK and Europe:
Jonathan Clowes Ltd.
10 Iron Bridge House
Bridge Approach
London NW1 8BD

In the US and the rest of the world:
Mrs. Andrea Plunket
Administrator
The Sir Arthur Conan Doyle Literart Estate
408 Debruce Road
Livingston Manor
New York 12758

For legal queries regarding the copyrights and trademarks:
In the UK
Dr Caroline McCarthy
78 Beak Street
London W1F 9DB

In the US etc.
Mrs. Andrea Plunket
(address above)

Enquiry form provided.

http://www.sherlockholmesonline.org/LicensingInfo/index.htm