Million Dollar Buff - S4.E2

Police "buff" Jennings Thornton, a thorn in the side for Malloy and Reed, intervenes in a drunk driving case, runs down a shooter after a robbery (and nearly getting Reed killed), and is finally arrested himself for falsely arresting two teenage boys for stealing mag wheels that were actually legally bought. Another case involves a woman who stole an expensive ring from a store, leaving a cheap one in return; the suspect is later arrested during a parking lot dispute and the ring is found on her during a search