125. The Court reiterates that where an individual makes a credible assertion that he has suffered treatment infringing Article 3 at the hands of the police or other similar agents of the State, that provision, read in conjunction with the State’s general duty under Article 1 of the Convention to “secure to everyone within their jurisdiction the rights and freedoms defined in ... [the] Convention”, requires by implication that there should be an effective official investigation. Such investigation should be capable of leading to the identification and punishment of those responsible. Otherwise, the general legal prohibition of torture and inhuman and degrading treatment and punishment would, despite its fundamental importance, be ineffective in practice and it would be possible in some cases for agents of the State to abuse the rights of those within their control with virtual impunity (see, among other authorities, Labita v. Italy [GC], no. 26772/95, § 131, ECHR 2000‑IV).
126. The investigation into serious allegations of ill-treatment must be both prompt and thorough. The authorities must always make a serious attempt to find out what happened and should not rely on hasty or ill‑founded conclusions to close their investigation or as the basis of their decisions. They must take all reasonable steps available to them to secure the evidence concerning the incident, including, inter alia, eyewitness testimony and forensic evidence. Any deficiency in the investigation which undermines its ability to establish the cause of injuries or the identity of the persons responsible will risk falling foul of this standard (see, for example, Kopylov v. Russia, no. 3933/04, § 133, 29 July 2010). Thus, the mere fact that appropriate steps were not taken to reduce the risk of collusion between alleged perpetrators amounts to a significant shortcoming in the adequacy of the investigation (see, mutatis mutandis, Ramsahai and Others v. the Netherlands [GC], no. 52391/99, § 330, ECHR 2007‑II, and Turluyeva v. Russia, no. 63638/09, § 107, 20 June 2013). Furthermore, the investigation must be independent, impartial and subject to public scrutiny (see Mesut Deniz v. Turkey, no. 36716/07, § 52, 5 November 2013). It should result in a reasoned decision to reassure a concerned public that the rule of law had been respected (see, mutatis mutandis, Kelly and Others v. the United Kingdom, no. 30054/96, § 118, 4 May 2001).
127. It falls to the State to have recourse to a procedure which would enable it to take all measures necessary for it to comply with its positive obligation of effective investigation imposed by Article 3 (see, mutatis mutandis, Sashov and Others v. Bulgaria, no. 14383/03, §§ 64, 68 and 69, 7 January 2010; see also Vanfuli v. Russia, no. 24885/05, § 79, 3 November 2011; Nechto v. Russia, no. 24893/05, § 87, 24 January 2012; and Nitsov v. Russia, no. 35389/04, § 60, 3 May 2012).
