Final answer:
Stevenson spends a long time telling McMillian's story to establish historical context, background, and elicit empathy from readers.
Step-by-step explanation:
In Stevenson's narrative, he spends a significant amount of time telling McMillian's story because it helps to establish the historical context and background of the character. By providing details about McMillian's experiences and struggles, Stevenson allows readers to understand the challenges and injustices faced by individuals like McMillian within the criminal justice system. This also helps to humanize McMillian and elicit empathy from the readers towards his situation.