In the New York Times, Christine Hauser writes a very good article about "desk duty" in the NYPD.
"An officer... spent more than 18 months watching surveillance video while authorities investigated an accusation that he had struck a suspect. [He] was eventually cleared of the charge."
In Baltimore they call getting mired in the department discipline process "jackpotting" because it's seen as random and doesn't necessarily have any relation to actually doing anything wrong.
One of the biggest complaints and fears of police officers is seemingly arbitrary discipline and the amount of time it takes to clear innocent officers from bogus charges.