Closed circle of suspects

The closed circle of suspects is a common element of detective fiction, and the subgenre that employs it can be referred to as the closed circle mystery. Less precisely, this subgenre – works with the closed circle literary device – is simply known as the "classic", "traditional" or "cozy" detective fiction.

It refers to a situation in which for a given crime (usually a murder), there is a quickly established, limited number of suspects, each with credible means, motive, and opportunity. In other words, it is known that the criminal is one of the people present at or nearby the scene, and the crime could not have been committed by some outsider. The detective has to solve the crime, figuring out the criminal from this pool of suspects, rather than searching for an entirely unknown perpetrator.