1) I agree with others, between the two pov shots you switch back and forth between the fear and nervous anticipation of being accused and the smug arrogance of the accuser
2) He uses it to build tension by putting the viewer in the position of the subject, with the fear etc that they are experiencing. By doing that the viewer has a more personal and vested interest in the story
3) The montages. The succession of clips to quickly tell the background story.