The show is known for its controversial portrayal of corrupt police officers and was originally advertised as "Rampart" in reference to the true life Rampart Division police scandal, which the show's Strike Team is loosely based upon.

The series focuses on the tension between a group of corrupt but effective cops and a captain torn between bringing them down and advancing his own political ambitions. The Shield stars Michael Chiklis (The Commish) as rogue cop "Det. Vic Mackey," leader of the elite Strike Team unit, who is effective at eliminating crime but who operates under his own set of rules. Benito Martinez (Outbreak & Her Costly Affair) plays "Captain David Aceveda," the young precinct head who doesn't like Mackey's tactics and wants to bust him off the force. And the Emmy-nominated CCH Pounder (ER & Boycott), plays "Det. Claudette Wyms," a veteran detective who understands Mackey and knows how to play both sides of the fence.