Timothy Marcia is a detective with the Open-Unsolved Unit of the Los Angeles Police Department's Robbery-Homicide Division, and the partner of Rick Jackson. He formerly worked as an investigator with the Hollywood Division homicide unit. In April 2004 he received a call from Harry Bosch in regards to cases Terry McCaleb had worked on for LAPD in the last few years. Marcia told Harry that the Chief had instituted a new program under which officers who had retired within the past three years could return to active duty without going back through the academy. Marcia told Bosch they especially need him in the Open-Unsolved unit because they had 7,000 unsolved cases.
By the Fall of 2011, he had been promoted to the position of "squad whip," where he "handled mostly supervisory and fill-in duties"; he also "mentored the young detectives and made sure the old ones didn't get lazy."
Detective Marcia is a real investigator with the LAPD Cold Case Homicide Unit, which he joined in 2001 after 15 years with the Department. The real Detective Marcia appeared in the short documentary Room 79 along with Michael Connelly and Rick Jackson.
Jackson and Marcia are both technical consultants for the series Bosch, and Marcia participated in the third and fourth episodes of the behind-the-scenes podcast series – "the Authenticity" and "the Inspiration" – along with Mitzi Roberts, Dorian Harris, and Pieter Jan Brugge.