The year before Walter Scott saw blue lights behind him, police in North Charleston stopped nearly 200 people a day for traffic violations.

A year later, about 100 motorists are pulled over on an average day.

Call it “the Walter Scott effect.”

Since Scott was stopped on April 4, 2015, millions have seen the video. It shows a white policeman shooting as the 50-year-old black man ran away. It led to the officer's arrest on a murder charge.

As the months passed, the police made fewer stops. All told, more than 26,000 people were pulled over in the nine months after the shooting, compared with 54,000 in the same period the year before — a 51 percent drop.

A Post and Courier analysis revealed this significant shift recently at a police agency beleaguered by allegations of excessive force, traffic stop quotas that buoy statistics and tactics that burden minority communities. It's likely, North Charleston officials said, that the impact of Scott's death on patrol officers played a role.

But their explanation of the drop — shown in two years of data obtained through S.C. Freedom of Information Act requests — has confounded critics who have long sought lasting changes to a practice they thought unfairly targeted impoverished black residents. And if crime continues creeping back up, some activists expect the relentless stops to come back.

“You could call this a 'Walter Scott effect' locally,” said Charles Epp, a University of Kansas political science professor who studies the intersection of policing and race relations. “But it's important to remember that this sort of reduction reflects broader pressure from the community to reduce the number of police stops for minor violations. The shooting of Walter Scott crystallized that pressure.”

For years, the police said stops of small-time traffic violators were needed to root out larger problems in a city once notorious for violence. The newspaper's examination of the practice last year found that North Charleston was pulling people over every eight minutes — by far the highest rate of any South Carolina law agency. Civil rights activists spoke out against the “pretext” or “investigatory” stops.

To the city's mayor, police chief and attorneys, the shift in approach doesn't mean the old effort was misguided. The reason for the decline in stops is complex, they said. They listed three possibilities:

A new philosophy of community policing that started long before the shooting.

A deterrent effect of the cameras that officers now wear.

The video of Scott's death that might be leading officers to subconsciously hold back from enforcement.

“Police officers are concerned about stops and how they are received,” Mayor Keith Summey said. “They are concerned about their perception in the public.

“Quite honestly, it may have affected some officers to do what's right instead of protecting their own.”

But the wider leniency for motorists might not last. Summey expressed alarm at the 10 homicides recorded in the first three months of the year. If the pace continues, 2016 would be the city's deadliest year to date.

“We do have some reservations,” the mayor said.

Community advocates and other residents are struggling to interpret the new landscape. They see fewer people stopped along Dorchester or Remount roads.

They thought the video of Scott's shooting would be a catalyst for reform at the North Charleston Police Department. The footage resonated among them and many others who decried police-involved deaths of black men. But no new policies on traffic stops have come from it, officials said, because the practice was never written down in the first place.

Without tangible evidence of change, perennial critics are disappointed. Ed Bryant, president of the NAACP chapter in the city, said he and other community leaders fear that old times could return as quickly as they left.

“They got caught with their hand in the cookie jar,” he said of the police and other city officials. “The only thing they're doing now is taking their hand out of the cookie jar. And there's not one policy change to show for it.

“The things that need to be put into place to make sure Walter Scott doesn't happen again — I haven't seen them yet.”

Patrolman 1st Class Michael Slager singled out Scott's old Mercedes-Benz on Remount Road because the third brake light behind the back window wasn't working.

Scott had been stopped at least twice before on North Charleston streets — once for failing to yield to merging traffic, another time for turning left at a red light.

For patrol squads like Slager's, an incentive program for making stops was still in place when he stopped Scott last spring, his attorney, Andy Savage, said after speaking with Slager and other officers. Top performers were rewarded with cheap coupons or administrative benefits, such as getting desired vacation days or shift requests, Savage said. In a courtroom last year, the attorney first referred to a quota system after learning of supervisors who commanded squad members to make at least three stops a day, he said.

“(Slager) observed what he was told to observe,” Savage said. “That was their sense of community policing. You look for a violation. You stop a vehicle. You stick your head in the vehicle, look around, and if there's nothing to it, you let him go.”

Scott, though, stumbled over Slager's questions about whether he owned the car. With a warrant out for his arrest for failing to pay child support, Scott soon jumped out and ran. Slager caught up, fired his Taser and scuffled with Scott as bystander Feidin Santana started filming with his cellphone. Slager's lawyer said Scott grabbed the stun gun and beat the officer. Santana's video showed the Taser fall to the ground as Scott ran again. Slager pulled his pistol and fired eight shots, five of which hit him from behind.

Based largely on the cellphone footage, which surfaced three days later, the murder case paints Slager as an executioner. But at a trial set for Oct. 31, his attorney plans to point out a lack of immediate backup for Slager and the alleged quota system as some of the circumstances leading to the officer's situation that day.

Police Chief Eddie Driggers, the mayor and the city's attorneys denied knowing that statistical benchmarks ever existed.

“From my lips to these ears,” Driggers said, “there has never been any type of quota.”

When asked in a public records request for any documentation of the practice, city attorneys printed about 25,000 pages from North Charleston's computer system. Few were pertinent.

In one email, the leader of an off-duty detail in The Park at Rivers Edge neighborhood cited one officer's disappointing performance: two stops in 44 hours on the job and two foot patrols done over 20 hours of work. As a result, he halved the officer's shifts, which the policeman had worked for extra pay, from about 20 hours monthly to 10.

“There has never been, nor will there ever be a quota for enforcement,” the leader wrote. “However, the lack of productivity in multiple areas raises concerns.”

The officer responded, saying he couldn't help it because most motorists he saw “don't break the law.”

Statistics, though, help supervisors gauge their officers' effectiveness, city attorney Brady Hair noted. It's possible that some ask for a certain number of stops daily from their squads, he said.

“And I don't see that as a problem,” he said. “We don't want them eating doughnuts.”

If not for an official quota, what was behind the incessant traffic stops?

Rewind to the start of 2014 — one year into Driggers' tenure as chief. His oral address to officers at the time marked a rethinking of the department's vision, city leaders said.

Under his predecessor, Jon Zumalt, patrol officers' de facto motto had been “own your zone,” the effort that ignited critics' comparisons to a military occupation of high-crime neighborhoods. That became “know your zone” under Driggers, who pushed officers to build relationships with residents and take up a “focused deterrence” approach by targeting the hard-core criminals.

But neither he nor the mayor said they implored department personnel to stop fewer people.

“As far as any directive,” Driggers said, “I expect people to make quality, well-documented cases that keep criminals behind bars.”

As time wore on, according to the officials' telling, the revised mission seeped into traffic enforcement and eventually showed in the statistics.

Officers pulled over more than 6,100 people in January 2015, a typical monthly tally in recent years. By the next month, the number fell to 5,300, then to 5,000. But the monthly total had dipped that low before.

In April, when Scott was killed, it hit 3,900 — the lowest in the past two years. And the decline didn't let up. By December, fewer than 2,300 people were stopped.

Such a drastic change appeared confined to North Charleston, though other areas of the state saw modest decreases, the newspaper's analysis found.

In 2014, from April through December, South Carolina police agencies gave out a monthly average of 241 warning tickets, the only statistic on traffic stops statewide tracked by the Department of Public Safety. The average after the shooting was 225 per month — a 7 percent drop.

Police in Charleston stopped 13 percent fewer motorists during the span, data from that city showed.

While observers think North Charleston's significant dip hints at a top-down policy decision, that's not true, the mayor and other officials insisted. That's not to say that the video had nothing to do with it.

“There wasn't a policy to make those stops, so there's no policy to change,” Summey said. “Maybe it's an adjustment in concept and attitude.”

The footage sent ripples through City Hall, from the mayor to the officers on the streets.

Officials were bombarded with inquiries from journalists worldwide. They ignored some because the questions being asked were not based on facts, the city's attorneys said.

A barrage of criticism also came their way for a news release issued before the video emerged, saying Slager had fired at Scott “to stop the threat.” Spokesman Spencer Pryor recalled how department officials “got beat up” for the statement they had spent hours to craft based on the information they had at the time from Slager.

The officer, though, has maintained through his attorney that his actions were justified.

Hair and Derk Van Raalte, his partner at the law firm that represents the city, said everyone in the building learned lessons from the heightened scrutiny. For one, the attorneys for the first time started analyzing statistics on traffic stops and examined other long-held criticisms of the Police Department.

“We know that the Scott event and the subsequent media coverage has changed a lot of these (officers),” Hair added. “It's changed everybody, and perhaps it's changed for the better.”

But he attributed many of the complaints to “people on the edges screaming” while a silent majority remained satisfied with officers' work to drive down crime and strengthen ties with the community. One day during the Scott shooting's immediate aftermath, he remembered, the media focused on protesters marching outside while the City Council's chambers were “full of black North Charlestonians” celebrating the Powder Puff youth football teams that the police support.

The attention on North Charleston, though, likely had some “psychological ramifications” on patrol officers, Hair said.

After the shooting, leaders took another step to pin a camera on every uniform, spending $85,000 in state grant money and $115,000 from a city fund for 251 of the devices. The move put them a step ahead of a law enacted later to require body-worn cameras on every South Carolina law officer.

North Charleston and its insurer also paid a $6.5 million settlement to Scott's family.

All of that could have accumulated in officers' minds and deterred them from making certain stops, Hair said. Similar theories have become known nationally as the “Ferguson effect,” in which officers fear public backlash after controversial police-involved deaths like the shooting of 18-year-old Michael Brown in the Missouri city.

The phenomenon is thought to bring about drastic declines in arrests and upticks in crime, though some statistics didn't support the concept in the wake of Brown's killing. Experts call it “de-policing,” said Samuel Walker, a criminal justice professor at the University of Nebraska at Omaha.

“Another perspective ... is that perhaps all that aggressive enforcement was unnecessary and counter-productive,” Walker said. “The heavy-handed enforcement creates a sense of oppression, particularly among African-Americans. Minor offenses, meanwhile, do not represent any great threat to public safety.”

Officers often make stops on these violations to investigate whether motorists might be up to more serious crimes. The so-called “pretext” tickets include unlit brake lights, which Slager noticed on Scott's car.

Some of the most dramatic reductions in North Charleston appeared in these offenses. Citations for defective brake lights and broken windshields went down 60 percent, from 382 during the last nine months of 2014 to just 154 in the nine months after the Scott shooting, according to Municipal Court data obtained through a public-records inquiry. Officers also wrote 79 percent fewer tickets for unlawful window tinting and 52 percent fewer for improperly operating lights.

If the pace lasts through June, the city's revenue from ticketing will fall $500,000 short of the $1.5 million it had budgeted.

Early data for 2016 indicate that the trend is holding. The Police Department cited motorists 2,048 times in January, halving its total of 4,144 in the same month last year.

But the loss, city officials said, is only a blip in the bustling city's $125 million budget.

While the changes could halt further damage to residents' pocketbooks, more must be done to mend past wounds, said Epp, the Kansas professor who co-authored “Pulled Over,” a book about police stops and their effects.

For one, he said, the department could devise a system for tracking the race of people ticketed. It does so now only for warnings, an official said in declining a request for the information.

The Charleston Police Department, for example, keeps racial data on all stops and released them to the newspaper. The records showed a greater burden on white people: Last year, about 48 percent of all black motorists stopped in Charleston actually got tickets while 59 percent of all white drivers were cited.

Also, Epp said, North Charleston should consider adopting a formal policy discouraging officers from making investigatory stops and take other steps to reach out and repair past damage in the community.

“That will take work and time,” he said.

But to the city's attorneys, the policing efforts never got a “fair shake” in the news media and among their longtime critics in the first place. Officers' disproportionate stops of black motorists is a natural “byproduct” of focusing patrols on high-crime areas where most residents are minorities, the lawyers said, pointing to maps showing how those demographics and crime overlap.

“It circles back around to whether (strict enforcement) is a good idea or a bad idea,” Hair said. “At one point, we get criticized for stopping too many people, and then when you stop stopping people the crime goes up.”

Reports of property crimes and violence during the nine months after Scott's death were up more than 17 percent over the same period in 2014. But it's only a short time span with a host of likely factors at play, and the police chief said the spike mirrored national trends.

Still, the mayor said he's concerned about a possible correlation between higher crime and the lower number of stops.

“We have to sit back and see what the end results are, and that will determine where we go,” Summey said. “You have to look at the numbers.”

Civil rights activists vowed to oppose any move to revive the stops, even if it's meant to fight a crime resurgence.

James Johnson, president of South Carolina chapters of the civil rights group National Action Network, said he never bought the crime-fighting benefit anyway, even as the city pointed to nose-diving crime statistics in past years as proof. North Charleston has fallen off rankings that once called it the seventh-most dangerous place in the country.

Johnson and the NAACP still want a federal civil rights investigation into the police force's old practices. Their plea dates back to the years before Scott's death. The U.S. Department of Justice didn't answer it then and hasn't yet after the shooting.

“If the numbers came out saying the stops were still going on after Walter Scott, the whole world would be against the city,” Johnson said. “It's not like they wanted to do this. They had to do it.”

A segment of the North Charleston community always will be critical of the Police Department, Summey said.

But if Scott's death can happen in this new age, activists asked, has anything really changed? City officials and community members alike expect it to take years for perceptions to shift.

Residents of the Chicora-Cherokee community off Spruill Avenue have seen sustained police activity over the years, along with some of the most entrenched problems with crime, poverty and mistrust of the authorities. The neighborhood president there, Anjene Davis, spoke in favor of reform after Scott's death.

Like other residents, he has noticed fewer of the blue lights that flashed behind Scott's car a year ago. In the long term, though, it doesn't solve the problem. At least, not yet.

“It is a welcome change to feel as though our area isn't a trap for being pulled over,” he said. “But it's going to take longer. It's going to take more intense conversation and deliberate action for those people who felt disenfranchised to feel appreciated and respected by their law enforcement.”

Tony Bartelme and Glenn Smith contributed to this report. Reach Andrew Knapp at 843-937-5414 or twitter.com/offlede.