Last Witness by Jilliane Hoffman

Nothing makes cops madder than the death of one of their own. When a spate of excessively violent cop killings befalls the Miami area, Special Agent Dominick Falconetti (himself a former cop), and his fiancee, C. J. Townsend, an assistant DA, team up to try to find the killer. Dominick's specialty is getting different factions to cooperate on a special task force, but in this case, all the participants--from federal, county, and city jurisdictions--are too busy marking their territories to do much crime fighting. The revelation that the victims were all "bad" cops of one kind or another doesn't do much to stop the infighting, despite mutual agreement that the slaughter needs to end. Meanwhile, C. J. fears a secret of her own (relating to the events in Hoffman's first novel Retribution, 2003) may relate to the murderer's motive. Not for the faint of heart, this chilling account combines all the ingredients of the high-concept thriller: violence, action, romance, political intrigue, and even a touch of humor.