Crime films are films which focus on the lives of criminals. The stylistic approach to a crime film varies from realistic portrayals of real-life criminal figures, to the far-fetched evil doings of imaginary arch-villains. Criminal acts are almost always glorified in these movies.

Films dealing with crime and its detection are often based on plays rather than novels^{[citation needed]}. Agatha Christie's stage play Witness for the Prosecution (1953; based on her own short story, published in 1933) was adapted for the big screen by director Billy Wilder in 1957. The film starred Marlene Dietrich and Charles Laughton and is a classic example of a "courtroom drama". In a courtroom drama, a charge is brought against one of the main characters, who says that they are innocent. Another major part is played by the lawyer (in Britain a barrister) representing the defendant in court and battling with the public prosecutor. He or she may enlist the services of a private investigator to find out what really happened and who the real perpetrator is. However, in most cases it is not clear at all whether the accused is guilty of the crime or not—this is how suspense is created.