Character mistake: Sergeant Gormley is promoted to Lieutenant in the previous episode. In this episode he is referred to as Sergeant Gormley by Commissioner Reagan and Deputy Commissioner Garrett Moore at least twice.
Character mistake: In this episode, Garrett says that "Nom de Guere" means pen name. It means war name. Nom de Plume means pen name and Garrett is supposed to be an expert in his field.
Answer: It's a common cop show plot device. If the police on the show always acted in the most logical way (i.e. not alerting a suspect to their presence) the show wouldn't have the opportunity for an exciting foot chase.