90 Resource book on the use of force and firearms in law enforcement It should only be used in situations of serious public disorder where there is the potential for violence that may cause loss of life, serious injury or widespread destruction. Considerations for its deployment should include media impact and availability of well-trained officers. It is essential that the capabilities of the equipment are fully understood prior to deployment and a tactical adviser specifically trained in the use of this equipment should be available. The use of a water cannon should be accompanied by the employment of law enforcement officers on foot.192 In order to meet the requirements of necessity and proportionality, the deployment of water cannons should be carefully planned and managed with rigorous command and control at a more senior level. Risks and how to mitigate these A water cannon should not be used indiscriminately against a crowd.193 In using a water cannon, it is important that law enforcement officials pay attention to the pressure that is being used, as when the pressure is too high it can knock people over, hit them on the head, or cause objects or debris to hit them, and may result in serious injuries. Water cannons should not be used against anyone who is unable to move, for example protesters who have locked themselves on a fence, older persons, injured persons or persons with disabilities, children and individuals at elevated height. There are also issues where law enforcement officials modify the water used in a water cannon.194 For example, in some countries, law enforcement officials use hot water cannons to prevent the water from freezing, as in cold climates where frozen water may lead to unintended injury or exposure. Law enforcement officers in some countries mix the water with chemicals. Although not expressly forbidden under international law, this is not recommended, as water mixed with chemicals bears a much greater risk of causing harm including physical pain, with effects that may last longer than those caused by tear gas. In some countries the water is coloured so it marks those who have been sprayed. However, there is no policing purpose for which such marking would be useful, in particular as it would have little value (if any) as evidence in a criminal trial. Electroshock weapons Description and use Electroshock weapons195 come in various forms, and new types are constantly being developed, including electroshock stun guns, shields, belts and batons. The use of electroshock weapons has grown exponentially, with currently more than half of all countries in the world using some type of electroshock weapon.196 See College of Policing, Tactical Options, 2014. The United Nations Special Rapporteur on the rights to freedom of peaceful assembly and of association has emphasized that water cannons should never be applied indiscriminately, never be used against peaceful protestors and never in such a way that the use itself result in an escalation of tensions. OHCHR, “South Korea: United Nations rights expert calls for independent investigation into lethal use of water cannon,” 28 September 2016, available from http://www.ohchr.org/EN/NewsEvents/Pages/DisplayNews.aspx?NewsID=20603&LangID=E 194  In some countries water from nearby, polluted rivers is used, with a high risk of spreading disease. This should be avoided. 195  Other terms can be used, including conducted energy weapon (CEW), electrical-discharge weapon (EDW), electronic control device (ECD), and the brand name “Taser” (often used as a catch-all term). 196  Ibid. 192  193