Crime films, in the broadest sense, is a film genre inspired by and analogous to the crime fiction literary genre. Films of this genre generally involve various aspects of crime and its detection. Stylistically, the genre may overlap and combine with many other genres, such as drama or gangster film, but also include comedy, and, in turn, is divided into many sub-genres, such as mystery, suspense or noir.
Screenwriter and scholar Eric R. Williams identified crime film as one of eleven super-genres in his Screenwriters Taxonomy, claiming that all feature-length narrative films can be classified by these super-genres. The other ten super-genres are action, fantasy, horror, romance, science fiction, slice of life, sports, thriller, war and western. Williams identifies drama in a broader category called "film type", mystery and suspense as "macro-genres", and film noir as a "screenwriter's pathway" explaining that these categories are additive rather than exclusionary. Chinatown would be an example of a film that is a drama (film type) crime film (super-genre) that is also a noir (pathway) mystery (macro-genre).
Crime films are often based on real events or are adaptations of plays or novels, or a remake or adoption of a previous film. Some plots are original and entirely fictional. For example, the 1957 film version of Witness for the Prosecution is an adaptation of a 1953 stage play of that name, which is in turn based on Agatha Christie's short story, originally published in 1933. The film version was remade in 1982, and there have been other adaptations. However, each of these media has its own advantages and limitations, which in the case of cinema is the time constraint.
Witness for the Prosecution is a classic example of a courtroom drama. In a courtroom drama, a charge is brought against one of the main characters, who claims to be innocent. Another major part is played by the lawyer (in England a barrister) representing the defendant in court and battling with the public prosecutor.