28 ANGUELOVA v. BULGARIA JUDGMENT example, mutatis mutandis, İlhan v. Turkey [GC], no. 22277/93, § 63, ECHR 2000-VII). 138. For an investigation into alleged unlawful killing by State agents to be effective, it may generally be regarded as necessary for the persons responsible for and carrying out the investigation to be independent from those implicated in the events (see, for example, Güleç v. Turkey, judgment of 27 July 1998, Reports 1998-IV, p. 1733, §§ 81-82, and Oğur v. Turkey [GC], no. 21594/93, §§ 91-92, ECHR 1999-III). This means not only a lack of hierarchical or institutional connection but also a practical independence (see, for example, Ergi v. Turkey, judgment of 28 July 1998, Reports 1998IV, pp. 1778-79, §§ 83-84, where the public prosecutor investigating the death of a girl during an alleged clash showed a lack of independence through his heavy reliance on the information provided by the gendarmes implicated in the incident). 139. The investigation must also be effective in the sense that it is capable of leading to the identification and punishment of those responsible. This is not an obligation of result, but of means. The authorities must have taken the reasonable steps available to them to secure the evidence concerning the incident, including, inter alia, eyewitness testimony, forensic evidence and, where appropriate, an autopsy which provides a complete and accurate record of injury and an objective analysis of clinical findings, including the cause of death (see, for example, concerning autopsies, Salman, cited above, § 106; concerning witnesses, Tanrıkulu v. Turkey [GC], no. 23763/94, § 109, ECHR 1999-IV; concerning forensic evidence, Gül v. Turkey, no. 22676/93, § 89, 14 December 2000). Any deficiency in the investigation which undermines its ability to establish the cause of death or the person responsible will risk falling foul of this standard. 140. There must be a sufficient element of public scrutiny of the investigation or its results to secure accountability in practice as well as in theory, maintain public confidence in the authorities' adherence to the rule of law and prevent any appearance of collusion in or tolerance of unlawful acts. The degree of public scrutiny required may well vary from case to case. In all cases, however, the next of kin of the victim must be involved in the procedure to the extent necessary to safeguard his or her legitimate interests (see Güleç, cited above, p. 1733, § 82, where the father of the victim was not informed of the decisions not to prosecute; Oğur, cited above, § 92, where the family of the victim had no access to the investigation and court documents; and Gül, cited above, § 93; for a full summary of the relevant case-law see McKerr v. the United Kingdom, no. 28883/95, §§ 111-15, ECHR 2001-III).