As Michael Brown’s death at the hands of Ferguson police officer Darren Wilson showed, in the wake of police killings, ousters of top officials are easier to come by than criminal charges of involved cops. But even harder than either of those accountability mechanisms is the task of instituting lasting, systemic change for the police agencies in question.

The Department of Justice, tasked with policing the police, has tools at its disposal to investigate and demand reform from police departments. But, in a new report published by The Marshall Project today, a combination of limited capacity, vague benchmarks for reform, and fluctuating levels of political will from DOJ agency heads have impacted how successful the federal government’s been able to be when it comes to reforming police departments.

It’s a story of the limits of federal oversight to exact change within police departments, and multiple, even cyclical attempts to get things right. If you’ve ever wondered what happens after the DOJ finishes up its investigatory and reform work, this is the story for you:

Simone Weichselbaum reports:

In Cleveland, where Attorney General Eric Holder appeared in December to decry a longstanding pattern of “unreasonable and unnecessary use of force” by the police, he neglected to mention that the Justice Department had investigated the city’s police a decade before. Justice officials settled that earlier case after the city promised to revise its policing methods.

In Cleveland, which was plagued by discrimination and excessive-force complaints, the Justice Department concluded a four-year investigation in 2004 by reaching an out-of-court settlement with the city. The deal, which Justice officials monitored for a year, included a prohibition against officers from firing at fleeing vehicles unless someone’s life was in danger.

But by 2013, Justice Department investigators were back in the city. This time they came at the request of the mayor, to look into another rash of police shootings and other issues. Among the problems they reviewed was a high-speed car chase that began when officers mistook the car’s backfire for a gunshot, and ended with a barrage of 137 police bullets that killed both the unarmed driver and his passenger.

“Obviously the reforms that were attempted there didn’t take hold,” Kappelhoff, the Justice Department official, said.