Who is Joel Bremmer from The Concrete Blonde and what is their importance?

A reporter for the Times, Bremmer is thirty five, with brown and thinning hair. He is overweight and wears a beard to cover the fact that his hair is thinning. The result makes him look older than his years. Bremmer wrote the book about the Dollmaker killer, largely using his sources at the police department and public records for its information. Worried about his reputation, he is less than pleased when things begin to go against Harry Bosch in court as it reflects badly on him. Still, he honorably refuses to reveal the source that is setting Harry up.