A/HRC/32/39 2010, an Angolan deportee died of a heart attack after being restrained by three security guards.30 In both cases, the detainees reportedly shouted that they could not breathe. 84. The responsibility to plan an appropriate operational response to an emerging situation applies as clearly to private security providers as it does to State law enforcement. However, in the case of private security providers there exists an additional potential precautionary step, namely to call upon the State’s law enforcement personnel. In circumstances where private security providers resort to force having turned down an opportunity to defer to the State’s police, their full compliance with the requirements of precaution would be called into question. In circumstances where help from authorities was forthcoming, private security providers can no longer justify the use of force under the principle of self-defence or defence of others. 85. Unless directly contracted by the State to do so, which is itself problematic, the contractual responsibility of private security providers in the context of assemblies is not to facilitate the right to freedom of peaceful assembly, but rather to protect the property or personnel of the contracting party. The protection of the rights and safety of the public more broadly remains the duty and function of the State. Private security providers should defer to properly trained and equipped specialist law enforcement units wherever possible. E. Operational conduct of private security providers 86. The two standards generally applied at the instant of an operation or exchange of force are necessity and proportionality. In the present section, the Special Rapporteur considers whether there are particularities to the application of those standards to the use of force by private security providers. 87. Necessity is a factual cause and effect assessment that evaluates whether force should be used at all, and if so, how much force is actually unavoidable in order to achieve the desired outcome. The requirement of necessity raises the question of whether the threat could not be averted by resort to less harmful means and, thus, implies a graduated approach to the use of force. Therefore, any use of force can be regarded as necessary only when it constitutes the least harmful means available at the time that can be expected to achieve the desired outcome. 88. The proportionality requirement relates to the question of whether the benefit expected to result from the use of force, that is, neutralizing a threat, justifies the harm likely to be caused by it. While establishing necessity requires a factual cause-and-effect assessment, demanding that the least harmful means be used to achieve a desired effect, proportionality entails a value judgment that balances harm and benefit, demanding that the harm that might result from the use of force is proportionate and justifiable in relation to the expected benefit. 89. As far as the right to life is concerned, the proportionality requirement demands that the use of firearms is permissible only if the purpose is to protect another life from a threat, and is sometimes called the “protect life principle”. The use of lethal or potentially lethal force to protect property or assert State authority does not meet the proportionality requirement. 90. Given that they are cumulative requirements, proportionality can place a ceiling on the level of force that may be considered necessary, and vice versa. For example, it may be 30 14 See BBC News, “Jimmy Mubenga: Deportee shouted ʽyou’re killing me’”, 4 November 2014. Available from www.bbc.com/news/uk-england-london-29902375.