Crime fiction that follows the realistic methods, bureaucracy, and teamwork of police investigations.
Police procedurals ground their mysteries in the actual mechanics of law enforcement: forensic evidence, interrogation techniques, interdepartmental politics, warrants, chain of custody, and the grinding teamwork of real investigations. The detective isn't a lone genius but part of a system, and the system itself, with all its flaws and frustrations, is central to the story.
Procedurals teach you to build tension from process. When the steps of an investigation become compelling, you've mastered a kind of storytelling that works in any genre: medical dramas, legal thrillers, even fantasy (the magical investigation). Understanding procedurals also keeps you from writing unrealistic investigations that pull readers out of the story.
Procedural investigation meets literary character study, showing how the subgenre can transcend its conventions.
The definitive modern procedural, showing how institutional systems shape (and fail) the investigation.
Write a scene where two detectives disagree about a piece of evidence. One thinks it's significant; the other thinks it's coincidence. Through their argument, reveal the evidence, advance the investigation, and show us who these people are. The procedure should reveal character.