Knox's Decalogue

Knox's Decalogue is series of rules codified in Ronald Knox's 1929 essay The Ten Commandments of Detective Fiction. In, the Decalogue is used as a tool and weapon for solving murder mysteries. The Decalogue is predominantly used by Dlanor A. Knox.

Knox's First
It is forbidden for the culprit to be anyone not mentioned in the early part of the story.

Knox's Second
It is forbidden for supernatural agencies to be employed as a detective technique.

Knox's Third
It is forbidden for hidden passages to exist.

Knox's Fourth
It is forbidden for unknown drugs or hard to understand scientific devices to be used.

Knox's Fifth
(not included)

Knox's Sixth
It is forbidden for accident or intuition to be employed as a detective technique.

Knox's Seventh
It is forbidden for the detective to be the culprit.

Knox's Eighth
It is forbidden for the case to be resolved with clues that are not presented.

Knox's Ninth
It is permitted for observers to let their own conclusions and interpretations be heard.

Knox's Tenth
It is forbidden for a character to disguise themselves without any clues.

Additional TIPS Information
The debate over the interpretation of these laws continues to this very day, and it has become the source of countless unfair controversies. While fundamentalists call any infringement upon these commandments heresy, revisionists point out that many canonized geniuses have violated these rules.

Trivia

 * Knox's Fifth is omitted from the Umineko version of the Decalogue. In the original text, Knox's Fifth is "No Chinaman must figure in the story," a rule responding to the then-contemporary trend of using foreign characters as villains.