Allegations of the use of excessive force by police departments in America continue to generate media headlines, more than two decades after the 1992 Los Angeles riots brought the issue to mass public attention and prompted law enforcement reforms. In Ferguson, Mo., a St. Louis suburb, the fatal shooting of teenager Michael Brown by a police officer in August 2014 has triggered unrest and protests. In New York, the July death of Eric Garner because of the apparent use of a “chokehold” by an officer has also sparked outrage. This follows other recent incidents and controversies, including an April 2014 finding by the U.S. Department of Justice, following a two-year investigation, that the Albuquerque, N.M., police department “engages in a pattern or practice of use of excessive force, including deadly force, in violation of the Fourth Amendment.”

Surveys in recent years with minority groups — Latinos and African-Americans, in particular — suggest that confidence in law enforcement is relatively low, and large portions of these communities believe police are likely to use excessive force on suspects. A 2014 Pew Research Center survey confirms stark racial divisions in response to the Ferguson police shooting, as well, while Gallup provides insights on historical patterns of distrust. According to a Pew/USA Today poll conducted in August 2014, Americans of all races collectively “give relatively low marks to police departments around the country for holding officers accountable for misconduct, using the appropriate amount of force, and treating racial and ethnic groups equally.”

Still, from a police perspective, law enforcement in the United States continues to be dangerous work — America has a relatively higher homicide rate compared to other developed nations, and has many more guns per capita. Citizens seldom learn of the countless incidents where officers choose to hold fire and display restraint under extreme stress. Some research has shown that even well-trained officers are not consistently able to fire their weapon in time before a suspect holding a gun can raise it and fire first; this makes split-second judgments, even under “ideal” circumstances, exceptionally difficult. But as the FBI points out, police departments and officers sometimes do not handle the aftermath of incidents well in terms of transparency and clarity, even when force was reasonably applied, fueling public confusion and anger.

How common are such incidents, both lethal and non-lethal, in the United States? Has there been progress in America? Without a doubt, training for police has become more standardized and professionalized in recent decades. A 2008 paper in the Northwestern University Law Review provides useful background on the evolving legal and policy history relating to the use of force by police and the “reasonableness” standard by which officers are judged. Related jurisprudence is still being defined, most recently in the 2007 Scott v. Harris decision by the U.S. Supreme Court. But inadequate data and reporting — and the challenge of uniformly defining excessive versus justified force — make objective understanding of trends difficult.

For perhaps the best overall summary of police use-of-force issues, see “A Multi-method Evaluation of Police Use of Force Outcomes: Final Report to the National Institute of Justice,” a 2010 study conducted by some of the nation’s leading criminal justice scholars.

Published federal statistics

The Justice Department releases statistics on this and related issues, though these datasets are only periodically updated: It found that in 2008, among people who had contact with police, “an estimated 1.4% had force used or threatened against them during their most recent contact, which was not statistically different from the percentages in 2002 (1.5%) and 2005 (1.6%).” In terms of the volume of citizen complaints, the Justice Department also found that there were 26,556 complaints lodged in 2002; this translates to “33 complaints per agency and 6.6 complaints per 100 full-time sworn officers.” However, “overall rates were higher among large municipal police departments, with 45 complaints per agency, and 9.5 complaints per 100 full-time sworn officers.” In 2011, about 62.9 million people had contact with the police.

In terms of the use of lethal force, aggregate statistics on incidents of all types are difficult to obtain from official sources. Some journalists are trying to rectify this; and some data journalists question what few official national statistics are available. The Sunlight Foundation explains some of the data problems, while also highlighting databases maintained by the Centers for Disease Control (CDC). The available data, which does not paint a complete national picture, nevertheless raise serious questions, Sunlight notes:

[A]ccording to the CDC, in Oklahoma the rate at which black people are killed per capita by law enforcement is greater than anywhere else in the country. That statistic is taken from data collected for the years 1999-2011. During that same time period, Oklahoma’s rate for all people killed by law enforcement, including all races, is second only to New Mexico. However, Oklahoma, the District of Columbia, Nevada and Oregon are all tied for the rate at which people are killed. (The CDC treats the District of Columbia as a state when collecting and displaying statistics.) In Missouri, where Mike Brown lived and died, black people are killed by law enforcement twice as frequently as white people. Nationwide, the rate at which black people are killed by law enforcement is 3 times higher than that of white people.

The FBI publishes statistics on “justifiable homicide” by law enforcement officers: The data show that there have been about 400 such incidents nationwide each year. But news investigations suggest that the rates of deadly force usage are far from uniform. For example, Los Angeles saw an increase in such incidents in 2011, while Massachusetts saw more officers firing their weapon over the period 2009-2013.

Academic estimates

A 2008 study from Matthew J. Hickman of Seattle University, Alex R. Piquero of the University of Maryland and Joel H. Garner of the Joint Centers for Justice Studies reviewed some of the best studies and data sources available to come up with a more precise national estimate for incidents of non-lethal force. They note that among 36 different studies published since the 1980s, the rates of force asserted vary wildly, from a high of more than 30% to rates in the low single digits. The researchers analyze Police-Public Contact Survey (PPCS) data and Bureau of Justice Statistics Survey of Inmates in Local Jails (SILJ) data and conclude that an estimated 1.7% of all contacts result in police threats or use of force, while 20% of arrests do.

Researchers continue to refine analytical procedures in order to make more accurate estimates based on police reports and other data.

Characteristics of suspects

Research has definitively established that “racial profiling” by law enforcement exists — that persons of color are more likely to be stopped by police. But while the cases of Rodney King in 1991 and Amadou Diallo in 1999 heightened the country’s awareness of race and policing, research has not uniformly corroborated the contention that minorities are more likely, on average, to be subject to acts of police force than are whites. A 2010 paper published in the Southwestern Journal of Criminal Justice reviewed more than a decade’s worth of peer-reviewed studies and found that while many studies established a correlation between minority status and police use of force, many other studies did not — and some showed mixed results.

Of note in this research literature is a 2003 paper, “Neighborhood Context and Police Use of Force,” that suggests police are more likely to employ force in higher-crime neighborhoods generally, complicating any easy interpretation of race as the decisive factor in explaining police forcefulness. The researchers, William Terrill of Northeastern University and Michael D. Reisig of Michigan State University, found that “officers are significantly more likely to use higher levels of force when encountering criminal suspects in high crime areas and neighborhoods with high levels of concentrated disadvantage independent of suspect behavior and other statistical controls.” Terrill and Reisig explore several hypothetical explanations and ultimately conclude:

Embedded within each of these potential explanations is the influence of key sociodemographic variables such as race, class, gender, and age. As the results show, when these factors are considered at the encounter level, they are significant. However, the race (i.e., minority) effect is mediated by neighborhood context. Perhaps officers do not simply label minority suspects according to what Skolnick (1994) termed “symbolic assailants,” as much as they label distressed socioeconomic neighborhoods as potential sources of conflict.

In studying the Seattle and Miami police departments, the authors of the 2010 National Institute of Justice report also conclude that “non-white suspects were less likely to be injured than white suspects … where suspect race was available as a variable for analysis. Although we cannot speculate as to the cause of this finding, or whether it is merely spurious, it is encouraging that minority suspects were not more likely to be injured than whites.”

Use of Tasers and other weapons

A 2011 report from the National Institute of Justice, “Police Use of Force, Tasers and Other Less-Lethal Weapons,” examines the effectiveness and health outcomes of incidents involving CEDs (conducted energy devices), the most common of which is the Taser. The report finds that: (1) Injury rates vary widely when officers use force in general, ranging from 17% to 64% for citizens and 10% to 20% for officers; (2) Use of Tasers and other CEDs can reduce the statistical rate of injury to suspects and officers who might otherwise be involved in more direct, physical conflict — an analysis of 12 agencies and more than 24,000 use-of-force cases “showed the odds of suspect injury decreased by almost 60% when a CED was used”; and (3) A review of fatal Taser incidents found that many involved multiple uses of the device against the suspect in question.

Other recent research has documented trends in the use of non-lethal force by officers in recent years, concluding that CED use has indeed been on the rise, while the use of hands and batons has declined.

Further reading: The coverage of such incidents by mass media has been studied by researchers, some of whom have concluded that the press has often distorted and helped justify questionable uses of force. A 2012 study in the Criminal Justice Policy Review analyzed the patterns of behavior of one large police department — more than 1,000 officers — and found that a “small proportion of officers are responsible for a large proportion of force incidents, and that officers who frequently use force differ in important and significant ways from officers who use force less often (or not at all).” Other research also finds that officers with more experience and education may be less likely to use force, while a review of case studies suggests that specific training programs and accountability structures can lower the use of violence by police departments. Finally, survey data continue to confirm the existence of undercurrents of racism and bias in America, despite demonstrable social progress; a 2014 Stanford study shows how awareness of higher levels of black incarceration can prompt greater support among whites for tougher policing and prison programs.

Keywords: crime, local reporting, racism, violence, police enforcement

Writer: John Wihbey | August 11, 2014