White Lightning - The Erin O'Reilly Mysteries, #20

You can't stop what you can't seeDetective Erin O'Reilly is used to people trying to kill her. She's carefully established a false identity as a killer for the Mob, while secretly working to bring it down from within. She thinks she knows where the danger is. But now a fiendishly clever assassin is stalking the streets, targeting New York's judges. His weapons are lethal traps, designed to kill without warning and look like freak accidents.
With one judge dead and another's life on the line, Erin and the rest of the Major Crimes squad race against time to track down a faceless, implacable murderer. To make matters worse, the mob war started by slick Mafioso Vinnie "The Oil Man" isn't over yet. Nobody holds onto a vendetta like the Mafia, and the blood hasn't stopped flowing. It's an electrifying case for Erin and her trusty K-9 Rolf as old enemies surface and loyalties clash, setting the stage for a shocking showdown in Manhattan's halls of justice.