Ferguson, Missouri. Cleveland, Ohio. Staten Island, New York. Eutawville, South Carolina.

In each place, individuals - all unarmed except for a child carrying a pellet gun - died at the hands of police officers. All of the dead were black. The officers involved, white.

To many Americans, it feels like a national tidal wave. Yet no firm statistics can say whether this spate of officer-involved deaths is a growing trend or simply a series of coincidences generating a deafening buzz in news reports and social media.

"We have a huge scandal in that we don't have an accurate count of the number of people who die in police custody," said Samuel Walker, emeritus professor of criminal justice at the University of Nebraska at Omaha and a leading scholar on policing and civil liberties. "That's outrageous."

There are some raw numbers, but they are of limited value.

The FBI's Uniform Crime Reports, for instance, track justifiable police homicides - there were 1,688 between 2010 and 2013 - but the statistics rely on voluntary reporting by local law enforcement agencies and are incomplete. Circumstances of the deaths, and other information such as age and race, also are not required.

The Wall Street Journal, detailing its own examination of officer-involved deaths at 105 of the nation's 110 largest police departments, reported last week that federal data failed to include or mislabeled hundreds of fatal police encounters.

Put simply: It's hard to know for certain what is happening on the ground.

"We want a comprehensive picture . . . so people can be aware of what really goes on, and not the claptrap put out by people with agendas," says David Klinger, a professor of criminology at the University of Missouri-St. Louis who has studied use of deadly force and hopes to get funding for a pilot project that could provide better national statistics.

To those who have taken to the streets to protest, that lack of context is almost beside the point.

"These are communities that have been living for generations under the yoke of what has felt like an occupying force," says Phillip Atiba Goff, co-founder of UCLA's Center for Policing Equity. "And regardless of what any of the stats are ever going to say, if we don't address the reality of that experience, then we're shooting ourselves in the foot in our attempts to make good on our promise of democratic principles."

String of cases

The high-profile cases have erupted one after the other.

On July 17, Eric Garner, 43, died after officers tried to arrest him on suspicion of selling untaxed cigarettes on a New York City street. Cellphone video captured the scene as one officer wrapped his arm around Garner's neck, and Garner repeatedly pleaded, "I can't breathe."

Tensions escalated on Aug. 9, when Officer Darren Wilson fatally shot Michael Brown, an unarmed, 18-year-old, in the St. Louis suburb of Ferguson.

On Nov. 22, a Cleveland officer shot and killed Tamir Rice, 12, after responding to reports of an armed man at a city park. Rice had been holding a pellet gun.

Two days later, officials announced that a grand jury had declined to return an indictment in the Brown case. Fires from the resulting protests in Ferguson had barely stopped smoldering when word came there would be no charges against the officer in New York City. Again, angry protesters marched.

One officer charged

Then a grand jury in Orangeburg County, S.C., returned a murder indictment Wednesday against a former small-town police chief in the May 2011 shooting death of an unarmed black man.

Richard Combs, who was the sole officer for the town of Eutawville, had been charged with official misconduct for shooting Bernard Bailey, who had come to the town hall to argue about a ticket his daughter had received. Combs' attorney questioned prosecutor David Pascoe's motives in seeking the murder charge.

"He's trying to make it racial, because his timing is perfect," John O'Leary said. "He's got all the national issues going on, so they want to drag him [Combs] in and say, 'Look what a great community we are here, because we're going to put a police officer who was doing his job in jail for 30 years.' That's wrong."

Walker, coauthor of the book The Color of Justice: Race, Ethnicity, and Crime in America, says much of the anger out there comes from years of conflict between black neighborhoods and law enforcement. "Within the African American community, there has been an experience of disrespect, offensive language, mistreatment in terms of stops and so on," he says. "And there's a sense that the police are out to get them."

It's not just the killings that have minority communities "fed up," says Inimai Chettiar of the New York University law school's Brennan Center for Justice.

"African American communities are tired of being over-policed, over-prosecuted, sent to prison, having men taken away from their communities, having families broken," says Chettiar, director of the center's Justice Program. "I think there's much more than just an instinctual sense that there is something amiss in these communities. I think people are tired of 'tough on crime.' "

Whether such incidents are on the rise, says Walker, "we're certainly more aware."

Goff has begun work on creating a policing database, with funding from the Department of Justice, the National Science Foundation, and private groups.

Chettiar is hopeful that recent events will create the "political and public will" to begin gathering and analyzing the facts. "In addition to personal stories," she says, "statistics help people change their minds."