Dirty cops versus dirtier cops. Backstabbers get blindsided. This is nothing new for L.A.P.D. procedurals. With “Street Kings” (formerly “The Nightwatchman”) Novelist James Ellroy (“L.A. Confidential”) writes a baroque intrigue, revised by Kurt Wimmer and Jamie Moss. As Captain Jack Wander, Forest Whitaker reprises part of his “Last King of Scotland” role. He’s moving up in the ranks. His undercover squad is notorious for hitting hard at low life. Fuck inquiries from Internal Affairs. His favorite is Detective Tom Ludlow, played by Keanu Reeves reprising personas from “A Scanner Darkly” and “Constantine.” Posing as a black-market arms dealer, Ludlow unleashes a blistering diss on Korean thugs. You “drive Jew,” he taunts. Says their eyes are shaped like “apostrophes.” It works. They beat the shit out of him and steal his car, which leads him to their lair. He slaughters the whole crew, rescues two kidnapped sex slaves from cages, then set-dresses the crime scene to make it look like self-defense. His superior covers up for this extra-legal crimestopper. As one officer puts it: “It doesn’t matter what happens. It’s how we write it up.” Ludlow, though, doesn’t have a clue that Wander is also a ruthless amasser of secrets and cash. When cop-killers frame Ludlow, he undertakes his own blue-on-blue investigation. South-Central native David Ayer (“Training Day”) sticks to gritty genre formula. The story recycles cliches like “Everything I touch dies,” but does sell existential cop-to-cop lines like “We’re all bad people.” The last-reel reveal, unfortunately, is weaker than the labyrinth leading into this heart of darkness. But “Street Kings” pays off as a rap sheet on a dirty do-gooder. With Hugh Laurie, Chris Evans, Jay Mohr, John Corbett, Cedric the Entertainer, Amaury Nolasco, Terry Crews, Naomie Harris, Martha Higareda, Common and The Game. 107m. Anamorphic 2.40 widescreen. (Bill Stamets)