Who is Sarah Downes from The Rag and Bone Shop and what is their importance?

Sarah Downes is Monument's assistant district attorney. She rides in the senator's limousine to pick Trent up for the Jason Dorrant interview, where she briefs Trent on the case during their ride from Vermont back to Monument. Sarah also informs Trent that Alicia's brother, Brad, confessed to the crime after Trent obtained the forced confession from Jason Dorrant.