ĐORĐEVIĆ v. CROATIA JUDGMENT 41 administered by private individuals (see, mutatis mutandis, H.L.R. v. France, 29 April 1997, § 40, Reports 1997-III). These measures should provide effective protection, in particular, of children and other vulnerable persons, and include reasonable steps to prevent ill-treatment of which the authorities had or ought to have had knowledge (see, mutatis mutandis, Osman v. the United Kingdom, 28 October 1998, § 116, Reports 1998-VIII, and E. and Others v. the United Kingdom, no. 33218/96, § 88, 26 November 2002). 139. Bearing in mind the difficulties in policing modern societies, the unpredictability of human conduct and the operational choices which must be made in terms of priorities and resources, the scope of this positive obligation must, however, be interpreted in a way which does not impose an impossible or disproportionate burden on the authorities. Not every claimed risk of ill-treatment, therefore, can entail for the authorities a Convention requirement to take operational measures to prevent that risk from materialising. For a positive obligation to arise, it must be established that the authorities knew or ought to have known at the time of the existence of a real and immediate risk of ill-treatment of an identified individual from the criminal acts of a third party and that they failed to take measures within the scope of their powers which, judged reasonably, might have been expected to avoid that risk. Another relevant consideration is the need to ensure that the police exercise their powers to control and prevent crime in a manner which fully respects the due process and other guarantees which legitimately place restraints on the scope of their action to investigate crime and bring offenders to justice, including the guarantees contained in Article 8 of the Convention (see Mubilanzila Mayeka and Kaniki Mitunga v. Belgium, no. 13178/03, § 53, ECHR 2006-XI; Members of the Gldani Congregation of Jehovah’s Witnesses and Others v. Georgia, no. 71156/01, § 96, 3 May 2007; and Milanović, cited above, § 84; see also, mutatis mutandis, Osman, cited above, § 116). 140. The Court will therefore examine whether the respondent State, in dealing with the first applicant’s case, has been in breach of its positive obligations under Article 3 of the Convention. (ii) Application of these principles to the present case 141. The Court notes at the outset that acts of violence in contravention of Article 3 of the Convention would normally require recourse to the application of criminal-law measures against the perpetrators (see Beganović v. Croatia, no. 46423/06, § 71, 25 June 2009, as regards Article 3, and Sandra Janković, cited above, § 47, as regards Article 8). 142. However, in the present case most of the alleged perpetrators were children below 14 years of age, against whom, under the national system, it is not possible to apply any criminal-law sanctions. Furthermore, in the specific circumstances in issue, it might be that none of the acts complained