- Anvilicious: Both the book and film have sections toward their endings that make it very clear how much Capote hated capital punishment.
- Award Snub: Truman Capote was highly annoyed that the 1967 film version wasn't nominated for the Best Picture Oscar, and yet the musical dud Doctor Dolittle was.
"Anything allowing a Dolittle to happen is so rooked up it doesn't mean anything."
- Broken Aesop: Many people find Capote's use of Hickock and Smith's executions as ammunition against the death penalty to be this. Though they didn't have the best of lives, many find their crime against the Clutters to be so heinous that they find the punishment more than fitting. Even Roger Ebert, a well-known critic of capital punishment, admitted that the film's anti-death penalty stance doesn't work because "the Clutters died for stupid, senseless reasons" and that most viewers would think that the killers did deserve to die.
- Harsher in Hindsight: Robert Blake, who played Perry Smith in the 1967 film, became a real life murder suspect in 2001.
- Ho Yay: The book has several instances of Hickock calling Smith "honey", and Smith remarks that he has "many thoughts of Dick" during their incarceration at Las Vegas. Given how Truman Capote was a well-known homosexual author and there were allegations that his relationship with the two killers exceeded "simply platonic", one has to wonder how much of this was unintentional.
- Older Than They Think:
- Although this piece of work is often credited as the first Non-Fiction novel, in fact In Cold Blood appeared nine years later than Operation Massacre, from the Argentinian journalist and writer Rodolfo Walsh. The late was published in 1957, and was well-known at the moment.
- Also Un millón de muertos (One Million Dead), from the spanish writer José María Gironella Pous, is from 1964, two years prior to Capote's work.