In In Cold Blood, detectives Nye and Church have a more "roundabout strategy" when it comes to interrogating Hickock. In the first interrogation, they never mention murder or give Hickock any idea as to why he is really being questioned. Nye and Church ask him all sorts of other questions, but nothing related to the murder. They do this purposefully to make him on edge and increasingly distressed, hoping Hickock will crack more easily.
Then, Nye takes a more pleading approach, trying to reason with Hickock for a confession. He presents the evidence of a boot print and tells Hickock that the prints are from his boots and that they have Perry's boot prints as well. This strategy could make Hickock believe that they already know it's him who's guilty and that there's no use in trying to deny it anymore.
But Nye goes further and breaks down the exact charges that Hickock will face because of his involvement in the killings of the Clutters. Nye delivers these counts matter-of-factly, like it's already a foregone conclusion that Hickock will be convicted. It also helps illustrate the severity of the crimes committed and that Hickock's name will be attached to it. Nye attempts to list the counts one by one, but he's cut off. Hickock cannot handle the idea of himself going down for the murders when he never actually pulled the trigger, so he confesses right then and there that, while he was involved, it was Perry who had done all the killing.
Altogether, the strategies employed by Nye and Church break Hickock down psychologically and appeal to his sense of dignity and responsibility.