A procedural mystery has as its key factor a blow-by-blow, thoroughly researched and specifically described analysis of how the crime is solved, by whatever means is the specialty of the main character. It may be authentically-researched detective legwork (as in a police procedural, such as in the novels of Joseph Wambaugh) or a scientific investigation of the evidence (such as in Patricia Cornwell’s books featuring the medical examiner Kay Scarpetta or Kathy Reichs’ series with forensic anthropologist Temperance Brennan).
In the 1940s the police procedural evolved as a new style of dectective fiction. Unlike the heroes of Christie, Chandler, and Spillane, the police detective was subject to error and was constrained by rules and regulations. As Gary Huasladen says in Places for Dead Bodies, “not all the clients were insatiable bombshells, and invariably there was life outside the job.” The detective in the police procedural does the things police officers do to catch a criminal. Writers include Ed McBain, P. D. James, and Bartholomew Gill