The purpose of the study was to produce scientifically valid results to inform law enforcement agency (LEA) executives' decisions regarding the use of Conducted Energy Devices (CEDs). The goal of the study was to produce practical information that can help law enforcement executives make good decisions about whether to deploy CEDs, and if a decision is made to deploy them, to help the agencies develop CED policy and procedural guidelines that provide increased safety for officers and citizens. In order to accomplish this goal, the objective was to conduct an evaluation comparing LEAs that have deployed CEDs to a matched group of LEAs that have not deployed CEDs in terms of officer and suspect safety during use-of-force incidents.
The study used a quasi-experimental design to compare Law Enforcement Agencies (LEAs) with Conducted Energy Device (CED) deployment to a set of matched LEAs that did not deploy CEDs on a variety of outcomes. The matching design used by this study involved matching seven CED deploying sites and six non-CED deploying sites based on violent crime levels, police activity, agency size, and population size of jurisdiction. The inclusion of 13 departments allowed the study not only to assess incident-level factors, but also some important departmental/organizational-level factors that could affect outcomes. The study included data collected for at least four years on all incidents of use of force for all of the participating departments. For the LEAs that deployed CEDs, data were collected for at least two years before CED deployment and two years of data after CED deployment. For the LEAs that did not deploy CEDs, data were collected for at least four years over a similar period. While the focus of the study was on the use of CEDs, data were collected on all use-of-force incidents (not just CED cases), in order to examine the range of weapons and unarmed tactics that the police employ in exerting force to arrest suspects. The researchers collected data in one of two ways, either a two-person research team was sent to the participating LEA to conduct onsite archival review and coding of use of force documents or they used electronic use of force data maintained by the participating LEA. Among the agencies with electronic data, some had good relationships with the Police Executive Research Forum, and opted to give the researchers their entire use of force dataset, rather than only four years of data. Using the raw data on each incident (Part 1), the principal investigators created computed/derived variables about selected incidents for use in hierarchical linear modeling analyses (Part 3). Additionally, aggregate data about each of the 13 sites were collected (Part 2); the research team worked with each site to collect crime and demographic data for each participating city. The sources of these data were the FBI's Uniform Crime Report (UCR) system and the United States Census 2000.
The principal investigators selected 18 police departments nationwide using a selection process designed to ensure comparability across the departments and to ensure that each department could provide the necessary outcome data. The goal was to have at least 12 departments in the study, and 13 were obtained. The selection criteria included: (1) being able to provide data on all incidents of use of force (including data such as type of force used and injury outcomes to both officer and suspects), (2) having a written policy identifying Conducted Energy Device (CED) and other less-lethal weapon placement on the force continuum, (3) a willingness to share data with the Police Executive Research Forum (PERF) for this study, and (4) having at least 100 sworn officers (larger law enforcement agencies were sought for participation in the study in order to obtain sufficient numbers of use-of-force incidents for a robust analysis). To ensure that appropriate groups could be compared to each other and that the time-series (pre- and post-test) component of the study could take place, the final criterion (5) was that the departments in the study needed to have all of the necessary data available for at least 4 years (2 years pre-CED deployment and 2 years post-CED deployment or 4 years of a comparable time period for the non-CED deploying sites). The selection of cities was based on a matching analysis using a PERF nationally representative survey on use of force, conducted in 2006-2007, which surveyed a stratified random sample of 950 Law Enforcement Agencies and received responses from just under 60 percent of the sample. The final sample includes all 17,965 use of force incidents for which data was gathered (Part 1) at 13 sites (Part 2). Part 3 includes a subsample of the incidents in Part 1, consisting of the 14,866 incidents that occurred at the 13 sites over 4 years selected by the principal investigators for analysis (2 years pre-CED deployment and 2 years post-CED deployment or 4 years of a comparable time period for the non-CED sites).
All law enforcement agencies in the United States that had at least 100 sworn officers according to the 2005 National Directory of Law Enforcement Agencies database.
law enforcement agency
United States Census 2000
law enforcement agency use-of-force documents and electronic use-of-force data
FBI Uniform Crime Report system
administrative records data
coded on-site observation
Part 1 has 774 variables describing each use of force incident. These include basic information about the incident (date, time, and type of call) as well as information about up to seven officers and up to seven suspects involved in each incident. These fall into a few categories:
- Background variables concerning the officers and suspects which include: physical descriptions, demographics, years of experience (officers only), and criminal history (suspects only).
- Variables describing behavior of the officers and suspects during the incident including: weapons available (officers and suspects), weapons used and specifically any use of Conducted Energy Devices (officers only), behavior during the incident (suspects only), and whether the suspect was impaired by alcohol/drugs or psychologically impaired, during the incident.
- Variables regarding injuries, for each of the officers, suspects, and for up to seven bystanders. These include: whether there was an injury, the cause and type of the injury, the severity of injury (including fatalities), and the level of medical attention required.
- There are also a number of computed variables, derived from the collected data, these primarily aggregate across multiple variables. These include aggregations across variables about a single individual (for example, the most severe suspect behavior, aggregating over the questions about different types of suspect behavior) and aggregations across individuals (for example: whether suspects were shot, aggregating over the seven suspects).
Part 2 has 24 variables, including 9 variables about demographic statistics (based on statistics from the 2000 United States Census) and 14 variables about crime statistics for each site (based on statistics from the FBI's Uniform Crime Report system).
Part 3 has 39 variables describing each use of force incident at the 13 sites. These include characteristics of the agency involved, the time period of the incident, suspect demographics and behaviors, injuries and deaths of officers and suspects involved in the incident, and weapons used in the incident. Unlike the variables in Part 1, variables in Part 3 do not concern individual officers and suspects, but are primarily derived variables concerning all officers and suspects involved in the incident.
Of the 18 law enforcement agencies that were selected for participation, 13 were included in the study, for a response rate of 72 percent.