It might vary a bit by country. In the U.S., anything written prior to 1930 is now public domain.
Dorothy Sayers, Lord Peter Wimsey series:
* Whose Body? (1923)
* Clouds of Witness (1926)
* Unnatural Death (1927)
* The Unpleasantness at the Bellona Club (1928)
* Lord Peter Views the Body (1928) (short stories)
S.S. Van Dine, Philo Vance series:
* The Benson Murder Case (1926)
* The Canary Murder Case (1927)
* The Greene Murder Case (1928)
* The Bishop Murder Case (1929)
1 Comment
It might vary a bit by country. In the U.S., anything written prior to 1930 is now public domain.
Dorothy Sayers, Lord Peter Wimsey series:
* Whose Body? (1923)
* Clouds of Witness (1926)
* Unnatural Death (1927)
* The Unpleasantness at the Bellona Club (1928)
* Lord Peter Views the Body (1928) (short stories)
S.S. Van Dine, Philo Vance series:
* The Benson Murder Case (1926)
* The Canary Murder Case (1927)
* The Greene Murder Case (1928)
* The Bishop Murder Case (1929)
Ellery Queen:
* The Roman Hat Mystery (1929)
[https://mysteriesahoy.com/public-domain-mystery-fiction/](https://mysteriesahoy.com/public-domain-mystery-fiction/)