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Back to Archives | Back to October 2010 Contents 

Police Use-of-Force Outcomes: Injuries and Control

By Geoffrey P. Alpert, PhD, University of South Carolina; and Michael R. Smith, JD, PhD, Georgia Southern University

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The findings reported in this article are part of a larger study funded by the National Institute of Justice. The findings within this report are those of the authors and do not necessarily represent the official positions of the National Institute of Justice or the U.S. Justice Department. Please direct all correspondence regarding this report to Geoffrey Alpert, Department of Criminology and Criminal Justice, University of South Carolina; call 803-777-6424; or e-mail

his study is concerned with injuries that may occur to police officers and citizens during use-of-force events. Previous research has shown that a very small percentage—just 1 percent or 2 percent—of police-citizen contacts involve the threat or application of physical force by the police, while arrests that result in force by police to control a suspect are estimated at 15 percent to 20 percent.1

While most uses of force are low level and involve officers’ hands, arms, and bodies to gain control of a suspect, some applications of force are more serious, including less-lethal devices such as pepper spray, batons, or conducted energy devices (CEDs), as well as the use of firearms.

Whenever force is used by the police or a suspect, there is a possibility of injury. Until recently, little was known about the frequency, causes, or correlates of force-related injuries. Over the past few decades, there have been advancements in training and technology with the goal of reducing the frequency and severity of injuries to the police and the public while maintaining safe and effective control over resisting suspects.

Technologies That Work

Oleoresin Capsicum (OC) spray, commonly known as pepper spray, was among the first of the “new” less-lethal weapons to achieve widespread adoption by police forces, while more recently, CEDs such as the Taser have gained popularity. CEDs have become well-known in recent years and industry estimates now place them in the hands of more than 12,000 police agencies. These two technologies were adopted, in part, with the hope of reducing injuries while maintaining control of combatant suspects. OC spray and CEDs have generated controversy and have been linked with in-custody deaths and allegations of overuse and even intentional abuse. Policy makers and law enforcement officials question whether CEDs are safe and effective and where, if at all, they should be placed on force continua that match appropriate police force options with levels of suspect resistance.

Overview of Methods

Several complementary research strategies were used to conduct the research reported in this article. First, a nationally representative survey of U.S. law enforcement agencies was conducted to provide a snapshot of how less-lethal force technologies, training, and policies are being used by state and local agencies. Second, agencysupplied use-of-force data sets from three agencies—Seattle, Washington; Miami-Dade, Florida; and Richland County, South Carolina—were analyzed separately in an effort to identify individual and situational predictors of injuries to officers and citizens during use-of-force events. Third, more than 24,000 use-of-force records from 12 police agencies were combined and analyzed using multilevel and fixed effects models to investigate the relationship between situational and policy-related factors and the likelihood of injury to police and citizens. Fourth, a longitudinal analysis was conducted that explored the effect on injury rates of the adoption of the Taser by the Austin, Texas, and Orlando, Florida, police departments. Finally, in-depth interviews were conducted with more than 250 officers and 25 citizens who were involved in use-of-force events in two midsize law enforcement agencies: one issued CEDs to its officers, and one did not. This article reviews what is known about the use of force and injuries, focusing on recent technological advancements, and presents findings and policy suggestions.

Literature on Police Use of Force and Injuries: A Brief Comment

Although the use of force by police has been studied for more than 40 years, research on injuries has been limited. The introduction of CEDs has raised additional questions concerning the safety of such weapons and their impact on injuries and in-custody deaths.2 In the 1990s, police found themselves in a similar position with respect to OC spray, as its use was spreading rapidly and concerns were being raised in relation to its misuse and safety.3 One interesting study, however, has looked at the use of OC spray, CEDs, and injuries in a broad perspective.4

Officer and Suspect Injury

In general, injuries to officers or suspects resulting from use-of-force incidents are infrequent relative to the overall number of police-citizen contacts. The analysis of injuries to officers in use-of-force encounters has provided mixed results with regard to frequency of occurrence, but estimates range from 10 percent to 38 percent.5 The 2002 National Survey of Contacts between the Police and the Public found that approximately 1.5 percent of citizens who had contact with the police reported that officers used or threatened to use force against them, with 14 percent of these respondents claiming they sustained an injury.6 A few studies moved beyond the general reporting on the frequency of suspect injuries to examine this likelihood relative to specific use-of-force tactics and weapons. For example, Meyer’s 1992 analysis of the Los Angeles Police Department use-of-force reports7 revealed that the use of a flashlight resulted in moderate or major suspect injuries in 80 percent of incidents in which it was employed. Punching suspects resulted in major or moderate injuries 64 percent of the time; the use of a baton, 61 percent of the time; and other bodily force, 46 percent of the time. Interestingly, officer use of older generation CEDs and chemical irritants resulted in no major or moderate injuries to suspects or officers.

The Present Study: National Survey

More than five hundred state and local agencies provided information on less-lethal force generally, and on their deployment and policies regarding CEDs in particular.8 In most agencies, line-level personnel carry batons (straight and/or expandable) and handheld chemical agents. Just under half of the agencies deploy CEDs to at least some personnel. At least three-fourths of the agencies that deploy the expandable baton, the CED, or personal-issue chemical agents deploy these weapons to at least half of their uniformed line-level patrol officers, deputies, and supervisors.

A large majority of agencies report the use of a continuum or model in policy and/or training to convey to their personnel the appropriate circumstances for using the various types of force authorized. More than half of those agencies had a model they described as “linear.” A full one-third of responding agencies had recently changed or were in the process of changing their continuum or model.

Scenarios were used to assess agency policy regarding the circumstances in which various types of force could be used. Most agencies allowed only soft, emptyhand tactics or control against a subject who refuses, without physical force, to comply with commands; just under half of the agencies would allow officers to use chemical weapons in this circumstance. If this subject, however, tenses and pulls when the officer tries to cuff him, a majority of agencies would allow chemical agents; hard, empty-hand tactics, strikes, and punches; and/or CED use. Forty percent of the agencies did not allow for the use of CED in probe mode in this tensing or pulling circumstance, but three-fourths did allow for CED use if the suspect fled, and almost all allowed for CED use when the subject assumed a boxer’s stance. The baton was reportedly not allowed by a majority of agencies in the scenarios until the subject threatened the officer by assuming a boxer’s stance.

As conveyed above, most agencies do not allow the CED to be used against a subject who refuses, without physical force, to comply with commands. Six in ten, however, allow for the use of a CED against a subject who tenses and pulls when the officer tries to cuff him. CED deploying agencies generally place the CED at the same level as chemical agents in their force continuum or model. Agencies vary as to the placement of CEDs relative to strikes or punches; CEDs are generally lower than impact weapons on a continuum or model.

For only one circumstance—subject near flammable substances—do a majority of agencies prohibit CED use. For most of the special circumstances or vulnerable populations listed in the survey, the agencies either made no particular mention of it in policy or restricted the CED use to special circumstances. A majority of agencies has no restrictions on CED use on a subject threatening deadly force, fleeing on foot, appearing emotionally disturbed, and/or seeming to experience excited delirium.

Single Agency Analyses

The Miami-Dade, Florida, Police Department (MDPD); the Seattle, Washington, Police Department (SPD); and the Richland County, South Carolina, Sheriff’s Department (RCSD) provided use-of-force data for analysis. Importantly, the three sites differed in that RCSD deputies and SPD officers could use OC spray, while the MDPD officers did not have that option, although all three agencies had CEDs. The findings from the RCSD indicated that the use of OC spray on suspects was one of the most important variables linked to a reduction in suspect injury, while CED use was unrelated to suspect injury. The data from the MDPD, whose officers did not have access to OC spray as an intermediate weapon, showed that the use of CEDs was associated with reductions in injury to both officers and suspects. The results from the SPD fell somewhere in between and showed CED-related injury reductions to suspects, but not to officers. Moreover, unlike in the RCSD, the use of OC spray in the SPD neither increased nor decreased the odds of injury to officers or suspects.

Whereas CEDs and OC spray, which typically are deployed at a distance from resistive or combative suspects, were associated with injury reduction, the use of hands-on tactics that require officers to be in close physical proximity to suspects to effect arrests was associated with an increased risk of injury to both officers and suspects, although some variations on this finding existed among the three agencies. Although the authors do not advocate the blind or wholesale substitution of intermediate weapons for handson tactics, the RCSD analysis suggests that some deputies were more likely to be injured while using soft-hand controls to subdue actively aggressive suspects. To the degree to which OC spray and/or CEDs would be authorized and appropriate for use in such encounters, their deployment in place of soft, empty-hand controls may help prevent some injuries, albeit mostly minor ones.

Multiagency Analysis

The authors used data from 12 agencies for their study; each of these agencies had appropriate use-of-force data and was able to export electronic files. Overall, CED use has been shown to reduce the probability of injuries to suspects across the 12 agencies in the combined analysis and in 2 out of the 3 agencies whose data were analyzed independently. Likewise, the relationship between OC spray and suspect injuries in the multiagency analysis is consistent with the injury-reduction finding at the RCSD. At the SPD, OC spray had no effect on suspect injuries, while the MDPD does not issue OC spray.

Longitudinal Analysis

The question to be addressed in this analysis is whether equipping officers with CEDs reduced injuries to officers or citizens, compared to injury levels before CEDs were put into use.

The Orlando, Florida, data comprise 4,222 use-of-force incidents aggregated to 108 months (1998–2006). The intervention (CED use) began February 1, 2003 (the 62nd month), with 21 CED deployments reported in the first month (there was a single prior CED use reported in August 2002). Thus, in Orlando, there were 61 preintervention observations and 47 postintervention observations. The Austin, Texas, data consist of 6,596 force incidents aggregated over 60 months (2002–2006), with preintervention and postintervention observations consisting of 30 months each.

In both cities, the adoption of the CED was associated with a statistically significant reduction in average monthly injuries to suspects. After the CED was adopted as a less-lethal alternative for patrol officers in Orlando, the rate of injury to suspects dropped by more than 50 percent compared to the rate of injury before the CED was put to use. In Austin, suspect injury rates were 30 percent lower after full-scale deployment of the CED than they were in the predeployment period. Reductions in officer injury rates were even greater in Orlando than for suspects; the average monthly rate of injury to officers dropped by 60 percent after the device was adopted. In Austin, injuries to officers also dropped, by 25 percent, after the device was deployed agency-wide.

Implications for Policy and Training

Based on the authors’ findings, the placement of OC spray and CEDs on a linear force continuum, which is used by more than half of the agencies surveyed, should be carefully considered. A typical resistance scenario involves an initial refusal by a suspect Implications for Policy and Training Based on the authors’ findings, the placement of OC spray and CEDs on a linear force continuum, which is used by more than half of the agencies surveyed, should be carefully considered. A typical resistance scenario involves an initial refusal by a suspect to comply with police commands, followed by the suspect pushing or pulling against an officer’s attempt to gain physical control and apply handcuffs. According to interviews with officers, many of these “wrestling matches” end up with the suspect and officer on the ground and the officer trying to use the ground for leverage. The authors’ analyses clearly show the increased risk for injury that such physical struggles carry with them. Furthermore, although suspects are injured more frequently than officers in use-of-force encounters, the increased risk for injury associated with soft, empty-hand control attempts is borne disproportionately by the police.

The authors’ findings consistently show a significant reduction in the risk of injury to suspects when CEDs or OC spray is used. This should not be surprising, as these weapons allow officers to control suspects from a distance without engaging in the hand-to-hand struggles that typically cause injuries. However, these weapons are not painless or risk-free. CED barbs often cause small punctures or superficial burns, and OC spray causes intense burning and irritation of the skin and mucous membranes. In very rare cases, people have died after being OC-sprayed or shocked with a CED, although no clear evidence exists that the weapons themselves caused the deaths.9 Also included in the risk-benefit calculus is the observation from the data that most injuries, either to officers or suspects, are minor and involve muscle strains, bruises, small cuts, or scrapes.

If injury reduction is the primary goal, then agencies that authorize OC spray and/or CEDs to overcome defensive resistance are clearly at an advantage based upon the results from the current study. Both of these less-lethal weapons help prevent or minimize physical struggles that cause injury, albeit relatively minor ones, to officers and citizens. Although both weapons cause pain, they reduce injuries, and based on the present state of the medical research, death or serious harm associated with their use is extremely rare. In that sense, CEDs and OC spray are relatively safe, and both are similarly effective at reducing the probability for injury. Both should be authorized as possible response alternatives to defensive (struggling to escape physical control) or higher levels of suspect resistance. However, the use of CEDs and OC spray must be closely observed and analyzed as overuse can be problematic.

The possible overuse of CEDs has several dimensions. First, CEDs can be used too often, that is, at inappropriately low levels of suspect resistance. This problem can be managed with policies, training, monitoring, and accountability systems that provide clear guidance and consequences to officers regarding when and under what conditions CEDS should be used and when they should not be used. In addition to setting the resistance threshold appropriately, good CED policies and training should require that officers evaluate the totality of the circumstances before using a CED, which would include the age, size, gender, apparent physical capabilities, and health concerns (for example, for obviously pregnant women) of suspects. Further, CED policies and training should prohibit the use of CEDs in the presence of flammable liquids or in circumstances where falling would pose unreasonable risks to the suspect (for example, in elevated areas or adjacent to traffic). Finally, policies and training should address the use of CEDs against persons who are restrained in handcuffs or are otherwise controlled and should either prohibit such uses outright or limit them to clearly defined, aggravated circumstances.

In addition to being used too often, CEDs can be used too much. Reported deaths in association with CEDs often involve multiple activations of a device or multiple cycles from a single device. In addition to having a very low rate of serious injury in epidemiological studies, controlled medical trials have shown CEDs to be safe on healthy adult volunteers for exposures of up to 15 seconds.10

Thus, CED policies should require officers to assess continued resistance after each standard cycle. Following the deployment of a CED, the suspect should be carefully observed by officers for signs of distress and should be medically evaluated at the earliest opportunity. ■


1Use of Force by Police: Overview of National and Local Data (Washington, D.C.: National Institute of Justice and Bureau of Justice Statistics, 1999), iii, (accessed September 2, 2010).
2American Civil Liberties Union, “Unregulated Use of Taser Stun Guns Threatens Lives, ACLU of Northern California Study Finds,” press release, October 6, 2005, (accessed September 2, 2010); Amnesty International, Canada: Inappropriate and Excessive Use of Tasers (London: Amnesty International, May 23, 2007), (accessed August 27, 2010).
3American Civil Liberties Union, Pepper Spray Update: More Fatalities, More Questions, June 1995, (accessed August 27, 2010).
4Michael R. Smith et al, “The Impact of Conducted Energy Devices and Other Types of Force and Resistance on Officer and Suspect Injuries,” Policing: An International Journal of Police Strategies & Management 30, no. 3 (2007): 423–446.
5Michael R. Smith and Mathew Petrocelli, “The Effectiveness of Force Used by Police in Making Arrests,” Police Practice and Research 3, no. 3 (2002): 201–215; Geoffrey P. Alpert and Roger G. Dunham, Understanding Police Use of Force: Officers, Suspects, and Reciprocity (New York: Cambridge University Press, 2004).
6Matthew R. Dunrose et al, “Contacts between Police and the Public, 2005,” special report (Washington, D.C.: Bureau of Justice Statistics, April 2007), (accessed September 2, 2010).
7Greg Meyer, “Nonlethal Weapons vs. Conventional Police Tactics: Assessing Injuries and Liabilities,” Police Chief 59, no. 8 (August 1992): 10–17.
8Michael R. Smith et al., “A Multi-Method Evaluation of Police Use of Force Outcomes: Final Report to the National Institute of Justice,” NIJ 231176 (July 2010), (accessed September 2, 2010).
9National Institute of Justice, Study of Deaths Following Electro Muscular Disruption: Interim Report, NCJ 222981, June 2008, (accessed August 27, 2010); Charles S. Petty, Deaths in Police Confrontations when Oleoresin Capsicum Is Used: Final Report (Washington, D.C.: National Institute of Justice, 2004), (accessed September 2, 2010).
10Smith et al., “A Multi-Method Evaluation of Police Use of Force Outcomes: Final Report to the National Institute of Justice”; Mark Kroll and Jeffrey Ho, ed., Taser Conducted Electrical Weapons: Physiology, Pathology, and Law (New York: Springer, 2009).

Please cite as:

Geoffrey P. Alpert and Michael R. Smith, "Police Use-of-Force Outcomes: Injuries and Control," The Police Chief 77 (October 2010): 108–115, (insert access date).



From The Police Chief, vol. 77, no. 10, October 2010. Copyright held by the International Association of Chiefs of Police, 515 North Washington Street, Alexandria, VA 22314 USA.

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