A first-person narrator in The Brothers Karamazov? That the narrator in fact steps in to say "I" may surprise you. It's easy to get lost in all the details of the book, but you might have noticed that the narrator pops in from time to time, generally getting into all kinds of seemingly meaningless digressions and apologizing for being such a terrible narrator. We never get his name; all we know for certain is that he is a local of the town, Skotoprigonyevsk, where everything takes place.
Through this narrator, Dostoevsky is able to have the best of both worlds. The narrator has just enough familiarity with everybody in the novel to be able to speak with the chumminess of a really good gossip. But he is also just vague enough that we don't pay any attention to him for much of the novel, when the drama of the Karamazovs takes center stage.
This unique narrative voice has drawn a lot of critical attention. Perhaps the most influential literary theorist on Dostoevsky is Mikhail Bakhtin, who argued that the peculiar invisibility of Dostoevsky's narrator enables the novel to relay a number of different voices: the narrator gives everybody a chance to speak for themselves. And given how much of the novel is taken up by dialogue – rather than the monologue of a single narrator or character – it might also be no surprise that Bakhtin calls Dostoevsky the master of a "polyphonic" ("multi-voiced") style in his Problems of Dostoevsky's Poetics.
Dostoevsky also embeds some hints about his narrative technique within the novel. Check out how both the prosecutor Ippolit Kirillovich and the defense lawyer Fetyukovich contrast their version of events with that of a novelist. The narrator himself steps in to give his opinion on both Kirillovich's and Fetyukovich's speeches. Kirillovich, he says, uses "a strictly historical method of accounting, which is a favorite resort of all nervous orators" (12.9.1). Basically, Kirillovich lacks imagination, which prevents him from grasping the way the world works and the real story behind Fyodor's murder. He tells everything – inaccurately – in chronological order.
Fetyukovich, on the other hand, speaks "somehow scatteredly at the beginning, as if without any system, snatching up facts at random, but in the end it all fell together" (12.10.1).
It seems to us that Dostoevsky is giving us a big, big hint here about how he thinks a narrator ought to tell a story. Reality is complicated, truth is complicated – so stories have to be complicated. Like the defense lawyer, our narrator seems to present events in a scattered away (for instance, he neglects to narrator Fyodor's murder...hello!) but that's because reality is scattered and hard to interpret.
Both the defense lawyer and the narrator sometimes have difficulty with the correct way of putting things, which helps make them more relatable to the reader. After all, haven't you ever found yourself tongue-tied in the face of a shocking or inexplicable situation? We witness the narrator's attempts to make sense of an astonishing torrent of events and piece together scattered shreds of reality, which we, then, must attempt to make sense of ourselves.