They don't, so the absolute best case outcome of "asking a police officer for immunity" is "nothing happens". The worst case outcome is that police officer tes

They don't, so the absolute best case outcome of "asking a police officer for immunity" is "nothing happens". The worst case outcome is that police officer testifying to a jury that you agreed to answer questions about a crime once you had immunity. This is a terrible plan that ends terribly for you. Smart people think they'll be able to logic and reason themselves out of the crosshairs of the criminal justice system. But they're playing a game they don't know how to play and the odds are stacked for the house.