In Cold Blood Narrator:

Truman Capote was never a guy to take the easy way out. That may be why In Cold Blood has two narrative styles but many narrators. Confused yet? Let us explain.

Third Person (Omniscient)

Much of the book has a third person omniscient narrator. This means that the narrator is all knowing and all seeing, like your mom or that friend of your roommate's that you can't stand. It also gives the narrator access to thoughts of all the characters. Capote generally reserves the right to take the wheel of narration, as it were, when there is a stunning descriptive moment to be served up to the reader. Look what he does with a simple look at the murder scene:

At the time not a soul in sleeping Holcomb heard them—four shotgun blasts that, all told, ended six human lives. But afterward the townspeople, theretofore sufficiently unfearful of each other to seldom trouble to lock their doors, found fantasy re-creating them over and over again—those somber explosions that stimulated fires of mistrust in the glare of which many old neighbors viewed each other strangely, and as strangers. (1.5)

Capote uses the third person omniscient narrator for much of the novel, but interestingly, not for the novel's most emotional scenes.

First Person (Central Narrator)

Although it is Capote's omniscient third person narrator who tells most of the novel's story, he turns over the novel's most compelling scenes—the story of the murder, the story of Susan Kidwell and Nancy Ewalt when they first find Nancy's body, the story of the execution of Perry and Dick—to characters within the story. What's that about?

It's Perry Smith who tells the story of the murder. After being arrested in Las Vegas, he's in a police car with Officers Dewey and Duntz when Dewey finally goads Perry into talking by telling him that Dick says that Perry had already killed an African-American transient a few years before. Perry introduces the story:

"[…] I thought, Why don't I walk off? [. . . ]I sure as Jesus don't want to go back in the house. And yet—How can I explain this? It was like I wasn't part of it. It was like I was reading a story. And I had to know what was going to happen. The end." (4.456)

It's then that the real story of the killing emerges (or at least, Perry's version of it).

Here's a tense moment, where the author, again, lets Perry narrate:

[. . .]Then [Dick] says to me [. . .] "I'm gonna bust that little girl." And I said, "Uh-huh. But you'll have to kill me first."[. . . .] Now that's something I despise. Anybody who can't control themselves sexually. I told him straight. "Leave her alone. Else you're gonna have a buzzsaw to fight."[. . .]So he says "Okay, honey. If that's the way you feel." The end of it was we never even taped her. (3.472)

Likewise, the story of the executions of Perry and Dick is told, not by the unseen narrator, but by a character in the story, in this case, Agent Alvin Dewey. Capote couldn't bear it and left The Corner before witnessing Perry's execution:

Dewey had watched them die, for he had been among the twenty-odd witnesses invited to the ceremony [. . .]As he was brought into the warehouse, Smith recognized his old foe, Dewey [. . .] he [. . .] grinned and winked at Dewey [. . .] Steps, noose, mask, [. . .] before the mask was adjusted, [Perry] spat his chewing gum into the chaplain's outstretched hand. Dewey shut his eyes; he kept them shut until he heard the thud-snap that announces a broken neck. (4.310-311)

Capote's trick of turning the more emotional scenes over to his characters has the value of lending those scenes an enormous sense of immediacy.