There are many possibilities. We'd need to know more context (the whole milieu described in the film). It might refer, for example, to betrayal of the police by taxi-drivers; or the spreading of jaundice in police stations, or something done by cowardly people... ;-)
Yes, in today's US context it's unlikely anything other than cowardice, particularly the cowards who don't keep up the tradition of cops blindly supporting other cops in all situations.
Yes, in today's US context it's unlikely anything other than cowardice, particularly the cowards who don't keep up the tradition of cops blindly supporting other cops in all situations.
Yes, that makes sense. According to IMDB the film is based on an Internal Affairs investigation (IAD is the police department that investigates police corruption).