Who is Rupert from The Pelican Brief and what is their importance?

Rupert is a bushy-haired character, first seen wearing a ball cap and Saints jacket, and claiming to be a sergeant in the New Orleans Police Department (NOPD), Rupert remains on the periphery of the novel. He drags a badly injured Darby Shaw to an unmarked car, and deposits her in the passenger's seat, where a partner in jeans and cowboy boots promises help after she answers a few questions.