GIULIANI AND GAGGIO v. ITALY JUDGMENT 49 Article 2. Furthermore, in keeping with the importance of this provision in a democratic society, the Court must, in making its assessment, subject deprivations of life to the most careful scrutiny, particularly where deliberate lethal force is used, taking into consideration not only the actions of the agents of the State who actually administer the force but also all the surrounding circumstances, including such matters as the planning and control of the actions under examination (see McCann and Others, cited above, §§ 147-150, and Andronicou and Constantinou, cited above, § 171; see also Avşar v. Turkey, no. 25657/94, § 391, ECHR 2001-VII, and Musayev and Others v. Russia, nos. 57941/00, 58699/00 and 60403/00, § 142, 26 July 2007). 177. The circumstances in which deprivation of life may be justified must be strictly construed. The object and purpose of the Convention as an instrument for the protection of individual human beings also require that Article 2 be interpreted and applied so as to make its safeguards practical and effective (see Solomou and Others, cited above, § 63). In particular, the Court has held that the opening of fire should, whenever possible, be preceded by warning shots (see Kallis and Androulla Panayi v. Turkey, no. 45388/99, § 62, 27 October 2009; see also, in particular, paragraph 10 of the UN Principles, paragraph 154 above). 178. The use of force by agents of the State in pursuit of one of the aims delineated in paragraph 2 of Article 2 of the Convention may be justified under this provision where it is based on an honest belief which is perceived, for good reasons, to be valid at the time but which subsequently turns out to be mistaken. To hold otherwise would be to impose an unrealistic burden on the State and its law-enforcement personnel in the execution of their duty, perhaps to the detriment of their lives and those of others (see McCann and Others, cited above, § 200, and Andronicou and Constantinou, cited above, § 192). 179. When called upon to examine whether the use of lethal force was legitimate, the Court, detached from the events at issue, cannot substitute its own assessment of the situation for that of an officer who was required to react in the heat of the moment to avert an honestly perceived danger to his life (see Bubbins v. the United Kingdom, no. 50196/99, § 139, ECHR 2005-II). 180. The Court must also be cautious in taking on the role of a first-instance tribunal of fact, where this is not rendered unavoidable by the circumstances of a particular case (see, for example, McKerr v. the United Kingdom (dec.), no. 28883/95, 4 April 2000). As a general rule, where domestic proceedings have taken place, it is not the Court's task to substitute its own assessment of the facts for that of the domestic courts and it is for the latter to establish the facts on the basis of the evidence before them (see, among many other authorities, Edwards v. the United Kingdom, 16 December 1992, § 34, Series A no. 247-B, and Klaas v. Germany,