to protect life’.189 Some of the most common situations in which police killings occur are during attempts to arrest suspected criminals;190 and to control a riot or crowd.191 4. Law enforcement officials must only use force when ‘strictly necessary and to the extent required for the performance of their duty’. 192 The circumstances in which it may be appropriate to use firearms include:       Self defence; Defence of others against the imminent threat of death or serious injury;193 To prevent a serious crime; To arrest a person presenting such a danger and resisting authority. Failure to attempt arrests, even in hostile territory, inevitably gives rise to suspicions that a State lacks evidence to place such persons on trial and therefore prefers to dispose of them arbitrarily;194 To prevent his or her escape; When less extreme means are insufficient.195 5. As to what is ‘necessary’, the use of firearms should be ‘only when less extreme means are insufficient to achieve these objectives’.196 Therefore using other means such as negotiation should be attempted first197 and if this proves ineffective then it may be permissible to escalate the level of force including through restraint.198 6. If the use of firearms is necessary, a ‘clear warning should be given with sufficient time for the warning to be observed’.199 Lethal use of force should only be carried out when ‘strictly unavoidable’.200 7. Force should also be proportionate, namely ‘proportionate to the seriousness of the offence and the legitimate objectives to be achieved’.201 189 Report on Police Oversight Mechanisms, A/HRC/14/24/Add.8, para 8. E/CN.4/2006/53/Add.4, para 42. 191 A/HRC/11/2/Add.6, para 72. 192 Code of Conduct for Law Enforcement Officials, Article 3. 193 Communication 45/1979 Suárez de Guerrero v. Colombia, 31 March 1982, para 13.3. 194 The UN Human Rights Committee has not allowed Israel’s justification of its policy and practice of assassinations on grounds of self-defence. Israel has claimed that it is not possible to arrest and try suspects, particularly where they are in areas controlled by the Palestinian Authority. See the Report of the Special Rapporteur on the situation of human rights in the Palestinian territories occupied by Israel since 1967 (E/CN.4/2004/6). 195 Basic Principles, Principle 9. Human Rights Committee, Communication 821/1998, Chongwe v. Zambia, 25 October 2000 para 5.2, See also Communication 859/1999, Jiménez Vaca v. Colombia, 25 March 2002, para 7.3. 196 Special Rapporteur on extrajudicial, Summary or arbitrary executions, A/61/311, 2006, para 41. 197 Basic Principles, Principle 4. 198 Code of Conduct, Article 3. 199 Basic Principles, Principle 10. 200 Basic Principles, Principle 9. 201 Basic Principles, Principle 5. 190 52