48 investigations into allegations of the use of excessive force.

38 investigations into allegations of discriminatory policing.

29 investigations into allegations of unlawful stops, searches or seizures.

Justice Department intervention is the only tool to force reform in America’s 18,000 law enforcement agencies nationwide. It was granted under a federal law, passed in the wake of a notorious incident of police violence: the 1991 case of Rodney King, a black man who was beaten by Los Angeles police after being stopped for speeding.

For the past year and half, FRONTLINE has been investigating how the DOJ process works, whether it works and how it’s changing. We’ve compiled a database of every investigation the Justice Department has conducted of police departments over the last two decades with a glimpse inside the stories behind the inquiry and what we know about their outcome.

Read the story:

Inside 20 Years of Federal Police Probes

Explore the interactive:

Fixing the Force

Watch the film (starting 6/28):

Policing the Police