Classic International Crime Fiction in the Public Domain

Plenty of older, classic crime stories, international and otherwise, are in the public domain and available free online. The University of Adelaide Library has Émile Gaboriau’s works for download or reading in English and the original French.

Project Gutenberg has thousands of free, public-domain books of all kinds online, including works by Gaboriau, Wilkie Collins, Poe, and many more.

(I'll try to update this if I come with more sites. Let me know if you find any. Thanks)