NYPD Blue's extra persons

NYPD Blue is addictive and Court TV is playing the episodes in sequence from the beginning. All I know about police detectives I’ve learned from TV or books so I’ve been wondering if the 5-6 detectives who we see as the main characters would be all a Lt. had to supervise? How large a group would Lt. Fancy be supervising in real life?

Also when the main characters go out to check on a suspect’s story, the suspect might be left in the coffee room and the detectives ask some extra person (without a speaking part) to go in and sit with the suspect while the detectives are gone. Who are these extra people? They seem to be just walking by when they get asked to stay with the suspect.

TIA,
Jois

I think the extra people are from anti-crime. They’re plainclothes cops that aren’t detectives.

–Cliffy