Knowledge Gaps Nix Firm Conclusions About CEW Risks, Experts Say

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A blue ribbon panel of experts assigned to determine “what is known and not known about the physiological and health effects associated with CEW use” has presented five “key findings” in a recently issued report:

  1. “[W]hile fatal complications [from CEW deployment] are biologically plausible, they would be extremely rare.”
  2. When a sudden in-custody death does occur, “CEW exposure cannot [reliably] be confirmed or excluded as the primary cause,” due to the limited scientific evidence currently available.
  3. “[O]verarching challenges in funding, conducting, and interpreting CEW research” have created critical “knowledge gaps” about the health consequences of CEW deployment.
  4. Filling these gaps will require significant improvement in the reporting and study of CEW use and its health effects in real-world settings and circumstances.
  5. “Because the electrical characteristics of CEW devices are variable and evolving,” each CEW model must be tested “on its own merit” to assess its “ability to induce incapacitation and potential adverse health effects.” The 100+-page report, titled “The Health Effects of Conducted Energy Weapons,” was commissioned by the Council of Canadian Academies and the Canadian Academy of Health Sciences. It can be accessed in full, free of charge, by clicking here.

[Editor’s note: For a comment from a TASER spokesman on the report and its findings, see the end of this article.]


The expert panel was comprised of 14 members from the US and Canada, representing a wide range of disciplines, including cardiology, pathology, psychiatry, forensic and emergency medicine, biomedical engineering, criminology, and the law.

Among them was an instructor for the certification course in Force Science Analysis, Dr. Christine Hall, an ER physician in British Columbia and an internationally recognized authority on excited delirium and less-lethal use of force.

In Canada as in the US, CEW use has expanded exponentially in recent years, and some critics have attempted to brand TASERs and other electronic control devices as dangerous instruments in light of at least 33 Canadian deaths “proximate” to CEW deployment.

As part of a government initiative to investigate the facts about alleged risks, the expert panel was assembled to review existing research, scientific literature, and technical documents and determine “what is known and not known” about the threat to health from CEWs.

Here are the principal findings, itemized in an Executive Summary of the group’s conclusions and expanded on in the full report:


Apart from obvious superficial injuries produced by CEW probes, some animal studies suggest the potential for more serious consequences, including respiratory complications and the disruption of heart rhythm.

So far as humans are concerned, though, there is not currently enough scientific evidence “to confirm the presence and magnitude of any [such] risk,” the panel writes. Moreover, the extent to which “co-factors common to real-world CEW incidents [e.g., intoxication, exertion, restraint, body type, existing health problems] that may increase susceptibility to adverse effects has not been adequately tested.”

The “absence of high-quality evidence” makes it “difficult to state any firm conclusions” about the specific impact of CEWs on the human body’s cardiac, respiratory, or hormonal systems, the panel notes. But generally speaking, the group concludes that statistically CEW discharges “rarely pose serious medical risks” and that “while fatal complications are biologically plausible, they would be extremely rare.”


“Sudden in-custody death resulting from a use-of-force event typically involves a complicated scenario that includes multiple factors, all of which can potentially contribute” to the fatality, the report says. These may include “agitation, physical or chemical restraint, disorientation, stress or exertion, pre-existing health conditions, and the use of drugs or alcohol. This makes it difficult to isolate the contribution of any single factor.”

Some evidence shows the potential lethality of CEWs’ electrical characteristics, the panel states, but “no evidence of a clear causal relationship has been demonstrated” by any large-scale, real-world study. Thus, the experts–again because of scarce and inadequate evidence–could neither confirm or exclude “at this time” the possibility that CEWs can cause sudden death.

However, they speculate, “If a causal relationship does exist, the likelihood that a CEW will be the sole cause of a sudden in-custody death is low.”


The panel identified five “overarching gaps in health-related CEW knowledge”:

  • Establishing a cause-and-effect relationship between CEW deployment and adverse consequences is “difficult” because “in many cases there is simply not enough research to make any definitive conclusions.” Particularly lacking is information on the relative impact other factors may have on a subject’s wellbeing in a use-of-force encounter.
  • There are no timeline guidelines. How soon after a CEW deployment must an adverse health condition occur for a causal effect to be reasonably considered?
  • There is a “paucity of knowledge of the health effects associated with CEW use outside” of controlled laboratory settings and unrepresentative test subjects. Experimental CEW research on human volunteers “typically involves healthy, physically fit volunteers” instead of “potentially vulnerable populations” engaged under realistic street conditions.
  • Research is seriously “hindered by lack of standardization and inconsistent reporting and record-keeping practices related to use-of-force events.” With few central registries receiving input from law enforcement and medical personnel, the ability to conduct meaningful analyses and form evidence-based conclusions regarding CEWs becomes exceedingly difficult.
  • There needs to be more independent research by individuals and organizations “without financial or other ties to CEW manufacturers.” Now many studies are done by researchers who get funding or support from sources that would appear to have conflicts of interest. “[T]hese studies may be scientifically robust,” the panel notes, but suspicion of bias “limits their widespread acceptance.”


The panel suggests several “strategies” for filling today’s knowledge gaps. These include:

  • Creating a central repository for information about CEW deployment and other uses of force, with LEOs and medical personnel submitting data on standardized forms.
  • Educating health care professionals so they can “more routinely perform examinations relevant for evaluating CEW effects.”
  • Conducting future studies to compare sudden in-custody deaths both related and unrelated to CEW use, to better assess the risk of CEWs in relation to other interventions.
  • Prioritize future research to address the most urgent questions about CEW use. These include documenting whether “the electrical characteristics of CEWs cause cardiac arrhythmia and sudden in-custody death in humans when deployed in real-world operational settings…whether “certain groups or individuals with particular conditions [are] at increased risk for adverse outcomes related to CEWs”…and [w]hat CEW design and deployment features could minimize the risk of adverse health effects.”


In principle, the panel explains, a CEW delivers “short-duration electrical discharges [that are] highly effective in stimulating nerves, causing incapacitation and pain, but are much less effective in stimulating the heart muscle and thereby inducing potentially fatal disruptions of…rhythm and pumping ability.”

However, the panel points out, “[s]pecifications between CEW devices are variable…and the variations…are constantly evolving, so knowledge based on any particular model does not necessarily translate to other devices, and the characteristics of newer devices are unknown.”

Consequently, the researchers write, scientifically “evaluating the intended and unintended effects” of CEW use requires testing each model “on its own merit.”

While many issues regarding CEW use have yet to be resolved conclusively, the panel is hopeful that its report will inform both law enforcement and the public about the current status of the CEW’s ongoing evolution from a novelty to a standard piece of modern police equipment.

As research continues, “public perception and emotion, although important considerations, should not lead the debate” about this device, the panel stresses. Ultimately, “a range of scientific inquiry, risk assessment, and evidence must guide policy” and practice regarding its use.


A spokesman for TASER International, manufacturer of the most popular CEWs, told Force Science News: “The Canadian report states over and over that there needs to be more and more study. However, it is imperative to point out that TASER CEWs, the most researched force option, have been used on humans more than 3.4 million times, of which over 2,000,000 are field uses.

“Yet, as the report states, there is no conclusive proof of a cardiac death caused by the electrical effects of a CEW. This is important information for putting the report in context.”

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