Final answer:
Donald Cullivan in 'In Cold Blood' offers a personal view of Perry Smith, contributing to a complex portrayal that prompts readers to consider the role of intellectual capacity in criminal culpability.
Step-by-step explanation:
The inclusion of Donald Cullivan in Truman Capote's 'In Cold Blood' is significant because it provides a personal perspective on Perry Smith, one of the murderers. Cullivan, a former army buddy of Perry's, visits him in prison and offers insight into Perry's character and background, creating a more nuanced portrayal of him. This inclusion challenges readers to consider deeper questions about morality and justice, such as whether intellectual capacity should impact one's culpability for criminal acts.