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Pepper Spray: Research Insights on Effects and Effectiveness Have Curbed Its Appeal

Date Published
May 1, 2019

Sidebar to the article Conducted Energy Devices: Policies on Use Evolve to Reflect Research and Field Deployment Experience, by Paul A. Haskins, published in NIJ Journal issue no. 281

Conducted energy devices (CEDs) were the second technology to expand law enforcement’s “less-lethal weapon” repertoire over the past quarter century. The first technology was pepper spray, or oleoresin capsicum (OC), an organic extract of the cayenne pepper plant that can stop most subjects cold — by temporarily blinding them, creating a burning sensation in the eyes and skin, and often affecting breathing.

By the early 1990s, OC was spreading quickly as a preferred use-of-force option for many agencies and officers.[1] As of 2013, an estimated 94% of all police departments had authorized the use of pepper spray, including 100% of all forces in jurisdictions with populations of 500,000 or more.[2] Yet its actual use by law enforcement would wane over time with the surge in popularity of CEDs among officers. As noted in a 2008 NIJ report, by then the CED had already “become the less lethal weapon of choice for a growing number of law enforcement agencies.”[3]

Several factors help account for the more constrained deployment of pepper spray as a standard policing tool today, including:

  • A more advanced understanding of pepper spray’s effects on subjects and officers.
  • A belief that pepper spray is less reliable than a CED activation, with a real risk that the spray will contact the officer, other officers, or bystanders, exposing them to the same symptoms as the subject. Research also has shown that OC is generally less effective than CEDs in subduing subjects.
  • Court decisions since 2000 making it clear that overuse or improper use of pepper spray can constitute excessive force in violation of the subject’s constitutional rights.

Development of Science on OC Safety and Effectiveness

A March 1994 report of NIJ’s Technology Assessment program observed that at the time, OC was “gaining acceptance and popularity among law enforcement officers and police agencies as a safe and effective method of incapacitating violent or threatening subjects.” The report emphasized, however, that there was “a lack of objective data on OC, its risks, and its benefits.”[4]

With NIJ’s support in ensuing years, data on OC inhalation by experimental subjects were gathered and analyzed. Sponsored by NIJ and the Office of Community Oriented Policing Services, a research team at the University of California–San Diego found no evidence that, when inhaled by volunteer subjects, OC “resulted in any additional change in respiratory function in the restraint position.”[5] The resulting 2001 report, however, had two important caveats: (1) Because the study was motivated in part by concern over reports that a number of arrestees exposed to OC in custody had experienced breathing-related deaths, the research focused on the effects of inhaled OC on respiration, and not on its ocular or vision effects when sprayed in a subject’s eyes — subjects wore goggles. (2) The study measured only the effects of OC sprayed for one second, as recommended by the manufacturer.

The “safe and effective” guidance was reinforced two years later. A 2003 NIJ Research for Practice report, Effectiveness and Safety of Pepper Spray, discussed outcomes of two NIJ-supported research studies that examined (1) both officer and subject injuries in three North Carolina jurisdictions and (2) 63 incidents nationwide in which suspects were sprayed with OC while being arrested and later died in custody. The report noted that the North Carolina research found that injuries to officers and suspects declined after pepper spray was introduced, and the second study determined that pepper spray contributed to only two of the 63 deaths and that both of those deaths were asthma-related. The report concluded, “The results of all studies in this Research for Practice seem to confirm that pepper spray is a reasonably safe and effective tool for law enforcement officers when confronting uncooperative or combative subjects.”[6]

Over time, however, concerns over pepper spray’s negative effects would emerge. The comprehensive 2010 multimethod evaluation of use of force, prepared for NIJ, examined law enforcement’s experience with OC spray in multiple jurisdictions and noted the following anomaly: Although OC application was associated with a decrease in subject injuries compared with injuries from other use-of-force options, OC was found to significantly increase officers’ injury risk: “For officers, the use of OC spray increased the probability of injury by 21 to 39 percent (depending on the model). This finding was unexpected and suggests that cases involving the use of OC spray differ from those involving CEDs in ways that were not accounted for in the models.”[7]

Separate research on 10 years of pepper spray injuries, as reported to the national poison control system, also noted disproportionate injuries among officers. Research by a University of California–San Francisco team, published in 2014, concluded that although there was a “low 1 in 15 potential risk for more severe adverse health effects in persons exposed to pepper spray that warranted a medical evaluation … the risk was highest when used for training law enforcement personnel and involved severe ocular symptoms.”[8]

The ascendancy of CEDs over OC was bolstered by evidence that CEDs were significantly more effective than pepper spray in subduing subjects. A 2017 report of research on the effectiveness of CEDs relative to OC observed, “The overall effectiveness of Tasers in this study is striking. In the overwhelming proportion of incidents where a Taser was used, once a Taser was used that incident came to an end. The same cannot be said with OC spray.”[9] The research, a single-site study of a large police department — more than 2,000 sworn officers — examined supervisor reports of use-of-force incidents and assessed the use and effectiveness of OC spray and CEDs.

Limited OC effectiveness and concerns over its safety for officers help account for the decline in popularity of pepper spray as a standard policing tool, culminating in a decision by some departments to no longer issue OC. As the Tampa Bay Times reported in October 2016, by that time four sheriffs’ offices in Florida had stopped issuing OC.[10] Pinellas County Sheriff Bob Gualtieri, explaining his decision to drop OC, told the newspaper that his 1,500 sworn deputies rarely used it and many no longer carried it — pepper spray was deployed only 15 times in the county in 2015. “The feedback from the bottom up was that it was no problem to get rid of it,” Gualtieri reportedly said. “It’s probably a tool ... that has had its day.”

Courts Have Restricted Permissible Use of OC

Courts have stepped in when pepper spray use is deemed objectively unreasonable. An often-cited representative case is the Ninth Circuit Court of Appeals’ 2002 decision in Headwaters Forest Defense v. County of Humboldt,[11] in which environmental protestors used a “black bear” metal device to lock themselves together but offered no physical resistance when law enforcement attempted to remove them. It was alleged that the officers repeatedly used pepper spray against the protestors, spraying full bursts from inches away and applying OC directly to the eyes of some protestors with Q-tips, while refusing for a long period to provide water for the protestors to wash off the OC to relieve their pain.

The court noted the following facts: (1) the use of pepper spray was unnecessary to subdue, remove, or arrest the protestors; (2) the officers could safely and quickly remove the protestors, while in “black bears,” from protest sites; and (3) the officers could safely remove the “black bears” in a matter of minutes with electric grinders. The court held that “it would be clear to a reasonable officer that it was excessive to use pepper spray against the non-violent protestors under these circumstances.” Upon finding that excessive force was used, the court held that the officers were not entitled to partial immunity from liability as public officials.

About This Article

This article was published as part of NIJ Journal issue number 281, published May 2019, as a sidebar to the article Conducted Energy Devices: Policies on Use Evolve to Reflect Research and Field Deployment Experience, by Paul A. Haskins.

Date Published: May 1, 2019