OLR Research Report

January 19, 2012




By: Veronica Rose, Chief Analyst


As of spring 2010, more than 12,000 law enforcement agencies in the United States, including many in Connecticut, have acquired conducted energy devices (CEDs), and more than 260,000 have been issued to law enforcement officials nationwide, according to a National Institute of Justice (NIJ) study. CEDs, such as Tasers, induce involuntary muscle contractions, temporarily incapacitating a person hit by the device. Law enforcement officers value CEDs as a highly effective alternative to deadly force (e.g., firearms). But several highly publicized deaths (including some in Connecticut) involving their use on subjects by law enforcement officials have fueled controversy over their safety.

An NIJ-sponsored panel of medical and other experts, which evaluated the safety and effectiveness of CEDs, reported in May 2011 that the devices, when used in accordance with national guidelines, are safe and create less risk of injury to officers and suspects than other methods involving use of force. According to the report, exposure to CEDs is not risk free, but there is no conclusive medical evidence that indicates a high risk of injury or death from their direct effects.

The study urges law enforcement officials to use the devices with caution and avoid using multiple or prolonged activations to subdue an individual because most CED-related deaths have involved multiple and prolonged discharges. It also recommends that law enforcement personnel (1) maintain an ongoing dialogue with medical examiners or coroners and emergency physicians about the effects of all use-of-force applications, including those involving CEDs, and (2) evaluate procedures involving life preservation, injury prevention, and evidence collection.


According to CED manufacturers, CEDs (otherwise know as electronic defense weapons) are designed to incapacitate or inflict pain on an individual from a distance without causing death or serious physical injury. Law enforcement officials favor the devices as an alternative to lethal force, contending that they (1) facilitate arrests of combative or noncompliant individuals and (2) can help reduce injuries to officers and suspects. But some people have died after being hit by CEDs during a law enforcement encounter. While many of the dead were chemically intoxicated or had some underlying medical condition, such as heart disease or mental illness, some were healthy adults. These deaths have raised questions and concerns over the safety of the devices.

In May 2011, NIJ published a report that addressed “whether CEDs can contribute to or be the primary cause of death and, if so, by what mechanisms.” The study was conducted in cooperation with the College of American Pathologists, Centers for Disease Control and Prevention, and National Association of Medical Examiners, with support from an expert medical panel. The panel consisted of forensic pathologists, medical examiners and specialists in cardiology, emergency medicine, epidemiology, and toxicology.

This report summarizes the major findings of the study.



In formulating its findings, the medical panel conducted mortality reviews of CED-related deaths and reviewed the current state of medical research on the effects of CEDs, including approximately 175 articles on the physiological effects of CEDs. It considered nearly 300 cases in which a law enforcement officer deployed a CED on an individual who later died and focused on 22 of these. In the vast majority of these cases, the original investigations concluded that CED exposure was not the cause of death. Based on its review, the panel concluded that “there is no conclusive medical evidence within the state of current research that indicates a high risk of serious injury or death from the direct or indirect cardiovascular or metabolic effects of short-term CED exposure in healthy, normal, nonstressed, nonintoxicated persons” (NIJ Report, p. 4). It found that the risk of death in a CED-related use-of-force incident in the general population is less than 0.25 percent (one in 400). Thus, “from a medical perspective, law enforcement need not refrain from deploying CEDs to place uncooperative or combative subjects in custody, provided the devices are used in accordance with accepted national guidelines and appropriate use-of-force policy” (id at p. 4).

The panel recommended that law enforcement officials (1) apply CEDs for no longer than 15 seconds at a time; (2) limit the number of discharges to the fewest needed to control an individual; and (3) regardless of how long the CED exposure lasts, provide some form of medical screening and ongoing observation to the person. This includes medical screening at the scene and ongoing monitoring for abnormal physical and behavior changes, which should be assessed by medical personnel.

CED Injuries and Severity

Based on case reviews and published studies of injuries in people exposed to CED, the panel concluded that the risk of significant injury from CEDs is low (less than 1%). The panel viewed this level as acceptable when compared to the potential benefits of CED use, such as (1) reductions in serious injuries to suspects and law enforcement officers and (2) the greater risks associated with other lethal and less-lethal options.

Significant injuries associated with CED use documented in the studies reviewed by the panel included (1) puncture wounds from CED darts and (2) secondary injuries. Secondary injuries can result from the use of CEDs (1) on individuals on tall structures or steep slopes because they could fall; (2) near flammable material, which could ignite from a CED spark; and (3) in water, where submersion could lead to drowning. CED use also presents a risk of interfering with implantable cardiac devices, such as pacemakers, although no bad outcomes have been reported.

Other Concerns

Heart Rhythms. Based on a review of pertinent research, the panel concluded that (1) there is currently no medical evidence that CEDs, when deployed reasonably, pose a significant risk for induced cardiac dysrhythmia (abnormal or irregular heartbeat) and (2) current research does not support a substantially increased risk of cardiac arrhythmias from CED exposure, even if the darts strike the front of the chest. These considerations make CEDs more favorable than other weapons in subduing combative or noncompliant suspects.

Respiration. The panel concluded that further study is needed on the effects of CEDs on respiration.

Stress. All aspects of an altercation, physical struggle, and physical restraint generate stress that may heighten the risk of sudden death in individuals who have a pre-existing cardiac condition or certain other diseases. Largely based on a review of prospective studies on human volunteers, the panel concluded that CED exposure may contribute to stress. But, in general, the stress from a CED discharge is comparable to stress from otherwise being physically restrained or subdued, and “medical research suggests that CED deployment during restraint or subdual is not a contributor to stress of a magnitude that separates from the other stress-inducing components of restraint or subdual” (id at p. 19).

Excited Delirium. “Excited delirium is one of several terms that describe a syndrome that is broadly characterized by agitation, excitability, paranoia, aggression, great strength and unresponsiveness to pain, and that may be caused by several underlying conditions, frequently associated with combativeness and elevated body temperature” (id at p. 21).

The panel concluded that “while studies in young, healthy drug –free volunteers suggest that CED deployment has inconsequential metabolic and stress-related effects, no human studies have been performed in situations modeling [excited delirium]” (id at p. 22). It therefore cautions that police officers, in deciding whether to use a CED, should be aware of behaviors related to excited delirium.

Safety Margins for CED Use. The panel concluded that most fatalities linked to CED use are in people who have other risk factors for sudden death. According to the panel:

The literature suggests a substantial safety margin with respect to the use of CEDs when they are used according to manufacturer's instructions. However, plausible mechanisms of injury do exist which make it impossible to exclude direct lethality in every case. The safety margins of CED use in normal healthy adults may not be applicable in small children, those with diseased hearts, the elderly, pregnant women and other potentially at-risk individuals. The effects of CED exposure in these populations are not clearly understood and more data are needed. All evidence suggests that the use of CEDs carries with it a risk as low as or lower than most alternatives (id at p. 24).

Prolonged Exposure to CED Application. The panel cautioned “that the medical risks of repeated or continuous exposure beyond the durations studied in humans are currently unknown, and the role of CEDs in causing death is unclear in these cases” (id at p. 27). But “most deaths associated with CED use involved multiple or prolonged discharges” (id).

If a death follows a CED deployment, the investigation needs to include consideration of information that may not be gathered in a routine death investigation or other in-custody death investigations. The report includes information that can be useful in establishing facts and which should be considered during the investigation of a CED-related death (id at 36).

Medical Care After CED Exposure. Medical personnel provide appropriate care to people hit by a CED discharge. According to the panel, “medical screening at the scene of the incident, the proper removal of dart(s), and the ongoing monitoring of individuals in custody for abnormal physical and behavior changes are crucial procedures. Suspects with implanted cardiac devices should receive outpatient follow-up as necessary” (id at p. 34).

For More Information

Read the final report, Study of Deaths Following Electro Muscular Disruption (pdf, 74 pages).

Read the NIJ Research in Brief, Police Use of Force, Tasers and Other Less-Lethal Weapons (pdf, 28 pages).

Read Police Use of Force: The Impact of Less-Lethal Weapons and Tactics in the NIJ Journal.

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