Is the narrative technique in Chapters 48-52 of Oliver Twist different from that in the rest of the novel?
In terms of structure, the narrative technique Dickens uses in Chapters 48-52 is in keeping with that previously established in Oliver Twist. He varies between chapters with heavy narration and chapters having light narration and much dialogue. He switches point of view as suits his needs as in an early chapter, Chapter 2, in which the point of view switches from indirect dialogue between workhouse Board members to direct dialogue between Mrs. Mann and Mr. Bumble (what a name...) to Bumble and Oliver, ending with Oliver and the workhouse authorities: "That boy will be hung!" Dickens also moves in and out in terms of narratorial distance by sometimes simply relaying events and at other commenting directly on the story:
Poor Oliver! He little thought, as he lay sleeping in happy unconsciousness of all around him, that the board had that very day arrived at a decision which would exercise the most material influence over all his future fortunes. But they had. And this was it: (Chapter 2)
All these structural techniques are also apparent in Chapters 48-52. For instance, Chapter 48 has heavy narration while 49 is almost exclusively dialogue. Narratorial distance changes between chapters as in Chapter 48 in which the distance is close and includes very direct narratorial comment (much in the vein of Hawthorne's manner of narratorial comment): "The sun- the bright sun, that brings back, not light alone, but new life, and hope, and freshness to man... ."
By contrast, the narrator is more distant in Chapter 51 and relays information without heavy comment: "They had not talked much upon the way; for Oliver was in a flutter of agitation and uncertainty which deprived him of the power of collecting his thoughts.... ." Further, as in earlier chapters, Dickens switches point of view to suit his needs. For example, the point of view is that of Sikes in Chapter 48 and that of Oliver in Chapter 51.
There are changes in other aspects of narratorial technique, most notable that of tone. Earlier chapters have amusement and irony in the narrator's tone, but in Chapters 48-52 that amusemnet and irony is largely eliminated and in its place is a tone of foreboding, as in 48, and doom, as in 50, and anticipation, as in 52.