Filming for "For I Have Sinned" took place both inside and outside the cathedral. The exterior is featured in establishing shots, and a brief scene of dialogue between Nick Knight and Father Rochefort; but it appears most prominently in the scene before Nick enters the church, leaving his partner, Schanke on watch outside in his car. The traditional church furniture and notable stained glass can be seen in these scenes, and lend much to the atmosphere of the episode.