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A number of recent incidents have reinforced renewed concern regarding states' use of so-called riot control agents (RCAs)⎯particularly tear gases and pepper spray⎯against civilians. The legitimacy of RCAs as a means to maintain and restore public order is based on two assumptions: first, that they do no long-term harm to their targets, and second, that they are used responsibly and appropriately. Yet the actions of security forces against civilian protesters from California to Cairo, Ramallah to Homs in recent months have added to a growing body of evidence that these so-called non-lethal weapons are not as safe as they seem and are not always employed as they should be.
Among the most recent cases, on 10 December, Mustafa Tamimi, a Palestinian man, died of injuries sustained the day before, allegedly from being hit in the face by a tear gas canister fired at close range by Israeli security forces during a regular weekly protest in Ramallah. In Cairo's Tahrir Square in November, police also fired tear gas at protesters at close range, resulting in several more such 'kinetically induced' injuries, according to media reports. November also saw a disturbing video of police using pepper spray against a peaceful sit-down protest at the University of California, Davis⎯an offshoot of the Occupy movement⎯making the rounds of the Internet.
In Tahrir Square, as in California, the protest was largely peaceful. In such cases, RCAs appear to being used not to control riots but to deter or remove people from a given location, or even to punish them for protesting. Such applications of riot-control agents, while by no means unprecedented, do not bode well at a time when non-violent public protest⎯against dictatorships, against the banking sector, against government-imposed austerity measures⎯seems to be a growing phenomenon around the world.
The limits of non-lethality
The 1992 Chemical Weapons Convention (CWC) defines a riot control agent as 'Any chemical not listed in a Schedule, which can produce rapidly in humans sensory irritation or disabling physical effects which disappear within a short time following termination of exposure.' (Scheduled chemicals are those subject to verification requirements under the CWC.)
The non-lethal nature of riot-control agents, and the rapid dissipation of their effects on humans, depend on their being used according to some fairly well recognized guidelines to prevent not only kinetically induced injuries but also high concentrations or prolonged exposure. Packed in a shell and fired at enemy forces, 'non-lethal' riot-control agents become banned chemical weapons.
The most commonly used riot control agents are chloroacetophenone (CN), ortho-chlorobenzylidene-malononitrile (CS), dibenz (b,f)-1,4-oxazepine (CR) and oleoresin capsicum (OC, or pepper spray). They are known as efficacious peripheral sensory irritants, creating irritating or noxious sensations due to their action on the sensory nervous system of the eyes, the respiratory tract and the skin. When RCAs are correctly used, these acute effects⎯however painful and distressing⎯wear off quickly in the vast majority of cases.
However, documented cases show that RCAs can have serious or irreversible effects ranging from cornea damage to chronic contact dermatitis or contact allergies to bronchoconstriction and respiratory arrest. The last two effects have been contributory factors in some fatalities.
Whereas it is widely claimed that RCAs have sufficiently high safety ratios (i.e. the difference between effective and lethal dosages are sufficiently far apart to minimize risk), the reality is often different for at least three reasons. First, in order to deprive targets of the chance to react with defensive or offensive action, security forces may be tempted to use RCAs in higher concentrations. Second, security forces may⎯inadvertently or negligently⎯greatly increase the risks from RCAs by using them in confined spaces, by exposing the same people to RCAs several times in a short period, or restraining targets⎯particularly hog-tying them⎯after exposure without decontaminating them.
Third, as for any other pharmaceutical agent, sensitivity to RCAs varies considerably within a population. The physically vulnerable⎯children and infants, the elderly, asthmatics, people with sickle cell traits and those with pre-existing heart or respiratory disease⎯are at higher risk of permanent injury and even death following exposure to even much lower than the recommended doses. Also, people who are extremely agitated, mentally ill, or under the influence of drugs or alcohol may be less reactive to RCAs and as a consequence receive greater or more prolonged exposure than is safe.
There is more to learn
States deciding whether and when to authorize the employment of riot control agents against civilians should have a full understanding of the potential health risks they pose. The toxic effects of any RCAs used should be properly studied by appropriate health authorities or independent bodies in a transparent manner. Technical guidelines for selecting and using RCAs should be further developed. Security forces should also receive appropriate training to minimize the risks of chronic health effects or death⎯and be held accountable if they deliberately or negligently put citizens at excessive risk.
Forensic pathology has a crucial role to play in all this. First, it can help in understanding the toxic effects of RCAs on the body, both acute and chronic. Second, based on a growing body of scientific evidence, it can help to demonstrate in court that RCAs⎯and, especially, inappropriate use of RCAs⎯are responsible for chronic health problems or fatalities.
However, in order to achieve a better understanding of the potentially lethal effects of RCAs, autopsy guidelines for forensic pathologists should be further developed, validated and applied in cases of suspected RCA-linked deaths. The existing international guidelines⎯the Minnesota Protocol (Model Protocol for a Legal Investigation of Extra-legal, Arbitrary and Summary Executions), developed by the United Nations in 1991⎯can be used in such cases, but a new and specific protocol would be more appropriate.
In order to prevent further deaths, injuries and long-term health problems, political and legal decision makers, as well as members of the public wishing to exercise their right to peaceful protest, should be informed by the best possible technical understanding of the known or suspected adverse effects of RCAs.
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