What is the purpose of dialogue in In Cold Blood?

Capote’s attention to detail and his ability to reproduce dialogue verbatim gives the book a hyper-real quality, glossing his authorial sleight of hand and allowing the reader to feel as though he or she is experiencing the events firsthand, unfiltered by the author’s point of view. Nevertheless, Capote himself admitted that in spite of the book’s realistic pretensions, it is a highly subjectivized, opinionated account; authors of so-called non-fiction narratives simply control the meaning of the story “by the selection of what you choose to tell.”

Capote's invention of conversations between the Clutters enabled us to garner a closer look at the family as a unit and as individuals. The family is an integral part of the story, but we only know them through descriptions given by neighbors, friends, and family. The dialogue Capote creates give them personality and shows us what they were like.