In 2012, Philadelphia police officers shot 63 people and killed 15, more than any other department in the country except Chicago. Charles Ramsey, who’d been the police commissioner for five years, didn’t like those numbers. He thought the shootings were justified, but he wondered whether his officers could resort to deadly force less often. So he did something local police are typically loath to do, on cases big or small: He called in the feds.

Federal intervention proved crucial to lowering the police shooting count in Philadelphia and in departments around the country in recent years. Shootings have fallen by 20 percent in the largest local departments since 2010, a VICE News investigation published last week revealed, with big cities like Philadelphia driving that trend. Seven of the 10 departments that saw the biggest drops went through federal investigations and adopted new policies, either through so-called collaborative reform or by order of a judge under a consent decree.

Despite that track record, and despite the intense public scrutiny on police shootings thanks to activism from groups like Black Lives Matter, the Justice Department under Attorney General Jeff Sessions is taking a big step back from oversight. Reform advocates and policing experts worry that without the support of the federal government, police departments lacking the resources — or the will — to change their approach to shootings simply won’t. Hundreds of preventable police shootings could go unchecked.

“I think Attorney General Sessions is retreating from police reform altogether,” said Vanita Gupta, who ran the Justice Department’s Civil Rights Division under President Obama. “He is pitting civil rights and crime-fighting against each other. That’s to the detriment of police-community relations today.”

A spokesman for the Justice Department did not respond to multiple requests seeking comment.

Sessions’ reversal is especially striking when we consider just how effective federal reform efforts have been. Since 2013, when Ramsey’s DOJ-backed efforts began, police shootings in Philadelphia have fallen by more than half. Other departments that went through collaborative reform or consent decrees saw similar drops, 27 percent on average in the first year, growing to 35 percent in subsequent years.

Ramsey worked with the Justice Department’s Community Oriented Policing Services Office to review Philadelphia’s policies around use of force. They found problems in police shootings across the board — in training, in transparency, even in the crime-scene photography of these incidents — and decided to make significant changes. In all, Philadelphia adopted 99 reforms over the next four years designed to put officers in less danger and reduce the need for lethal force. Philadelphia cops shot 23 people last year, fewer per capita than smaller cities such as Denver and Indianapolis.

“It had a huge impact on the department,” Ramsey said of the federal reform effort.

Current Philadelphia Police Commissioner Richard Ross agreed. He said that an improved accountability procedure he’d tried to put in place 10 years earlier had failed until the collaborative reform process began.

Indeed, police chiefs, activists, and former Justice Department officials all credited federal intervention with helping to reduce the number of police shootings and pushing through reforms that might otherwise have failed.

In other cities that saw federal intervention in recent years, such as Chicago and Cleveland, the Justice Department made a variety of recommendations. These included new use-of-force policies; training for officers to deal with realistic scenarios; and a streamlined, independent process to review shootings when they occur. In Chicago, police shootings dropped by more than 40 percent the year the DOJ proposed a consent decree, and in Cleveland they fell by 75 percent.

Before a shooting ever begins, officers are guided by policies that govern how they can respond to deadly threats. Policies that discourage the use of lethal force tend to include language about the sanctity of life, the need to de-escalate dangerous situations, and the importance of exhausting every other option before firing a service weapon. Those policies act as a signal to officers and supervisors that extreme use of force will not be tolerated.

In some cases, the Justice Department simply recommended clarifying these policies to address specific scenarios. For example, Philadelphia explicitly banned officers from firing at or from a moving vehicle, in part because those bullets could hit bystanders.

In addition to updated policies, experts suggest shootings can be avoided with training courses that put officers through realistic scenarios and teach them about crisis intervention to talk down people in mental crisis. Philadelphia officers have found crisis-intervention training so useful that there's now a waiting list for the course, Ross said.

Accountability for shootings when they do happen can also serve as a deterrent to future incidents, experts said. An officer who knows he’ll have to go through a thorough review may be more careful about firing. In Philadelphia, the department streamlined investigations in order to deliver results more quickly.

“I think when they work together, all these things help,” Ross said. “Clearly they help with transparency and credibility in the community.”

Changing the approach to shootings can also have broader impacts. Several departments that tracked their reforms showed marked declines in use of force overall. This suggests that these policies can improve policing more generally, and not just in the handful of incidents each year that escalate into shootings.

“The systems that we would put in place to reduce shootings are the same systems that are necessary to reduce force in general,” said Ron Davis, who was the director of the COPS office until January and now works as a policing consultant.

When Sessions took office this year, the DOJ had 19 ongoing reform agreements with police departments, including Baltimore and Cleveland.

In March, Sessions ordered a review of all these agreements and announced his intention to scale back federal intervention. The Justice Department has stopped the COPS office from participating in any further voluntary reforms, and little progress has been made on existing agreements. Reports on DOJ investigations into the Milwaukee and North Charleston Police Departments have yet to be released, despite requests from local leaders.

“I think what this administration has taken away is a significant tool for helping to drive change and accountability for policing in this country,” Davis said.

Critics of consent decrees, including Sessions, argue that they hamstring police officers who need freedom to do their jobs. Too much scrutiny of cops, they say, has a chilling effect on policing and has already led to a rise in violent crime — a phenomenon some call the “Ferguson effect,” after the reaction to the 2014 police killing of Michael Brown near St. Louis.

“Look at the enforcement across the board: It’s on the decline,” said Tony Barksdale, a former deputy commissioner of operations in the Baltimore Police Department. “The term they use is de-policing, the Ferguson effect, whatever. I look at the statistics: When you have crime going up, when you have cases going unsolved, that means the criminals are winning.”

Murders did increase in Baltimore this year, after the department’s consent decree went into effect in January. But they fell in the wake of an earlier voluntary policing collaboration with the federal government in 2014. Overall, murders in cities whose police drew federal oversight went up by 18 percent in the years following reforms, in step with rising homicide rates nationally.

A long-term reduction in police shootings doesn’t have to depend on federal intervention; reform-minded police chiefs swap strategies, and smaller law enforcement agencies have copied specific language from Philadelphia’s use-of-force policy in their own reform efforts, for example.

It’ll be harder for these ideas to spread without Sessions’ support. “Now that the DOJ doesn’t do [collaborative reform], then how does the field do that?” Davis said. “Most cities, big and small, don’t have the resources.”

Still, Davis, Ramsey, and others are optimistic. They say departments around the country have already seen the value of reforms.

“It’s not dead by any stretch of the imagination,” Ramsey said. “Whether we have the Department of Justice behind us or not, we’ve got to move forward, and move ahead as a profession.”