Police corruption in New York, in Right to Remain Silent, an episode of This American Life from September. The show also includes another tale similar to the Twitter joke trial story.
Anti-police insurgency in Russia’s far east, The Primorsky Partisans, from BBC Radio 4’s Crossing Continents and broadcast in November. Also as an MP3.
Not radio: Axe Cop comics, via Mr Bowbrick.
Added: Buster Keaton in Cops, at Archive.org.