In what ways do the alternating naratives between past and present in Jodi Picoult's novel Nineteen Minutes enhance the story?

Jodi Picoult's novel are known for innovative twists and unusual
deliveries. Nineteen Minutes is no exception. The issue here is the bouncing
back and forth from past to present. This accomplishes a couple of
things.

The first thing this accomplishes is it keeps the reader on
his or her toes. Sometimes, spending the entire story in the present tense, readers have a
tendency to become complacent in the reading of the novel. We know what to expect, and our
attention can relax. Jumping back and forth, keeps the reader's mind
involved.

The second thing this does is establishes a means of
successfully fulfilling her goal with the novel. From very early on in the novel, we know the
fatalistic outcome. We also know that the protagonist's daughter is going to be swept up in this
fatalistic outcome. Switching back and forth creates a more sympathetic audience for the
conclusion as we can almost understand the progression of the tragedy.