I am writing about a woman. She is a US homicide detective. Is “detective” a job description or a title? That controls whether to capitalize or not, correct? For instance, when she’s introduced to someone, do I write, “This is Detective Kit Mangini?” When reference is made to her within the body of a sentence, ., “We received the letter, detective, that’s why we’re here”, is detective capitalized in that instance? Also, in the previous sentence, specific to that sentence alone, is the comma properly placed outside the quote marks before the word is?