Agatha Christie published her first novel, The Mysterious Affair at Styles, in London in 1920, introducing detective Hercule Poirot. The novel hinged on minute physical and chemical evidence — specifically the timing and chemistry of a strychnine poisoning — as the basis for criminal investigation. Christie, who had worked as a hospital dispenser during World War One at Torquay, Devon, drew on her pharmacological expertise to construct evidence puzzles of extraordinary technical precision, establishing a new standard for toxicological evidence in crime fiction.

Christie went on to become the best-selling novelist of all time, and her work shaped global popular understanding of criminal evidence for over a century. Her plots trained millions of readers to think about physical evidence, timing, chemistry, and witness reliability as tools of detection. Her influence on later crime writers is incalculable, and her fictional evidence methods — always centring on a specific, often chemical, clue — set the template for the classic detective novel as a literature of evidence analysis.