22 ANGUELOVA v. BULGARIA JUDGMENT United Kingdom, judgment of 27 September 1995, Series A no. 324, pp. 4546, §§ 146-47; Salman v. Turkey [GC], no. 21986/93, § 97, ECHR 2000VII; and Velikova v. Bulgaria, no. 41488/98, ECHR 2000-VI). 110. In the light of the importance of the protection afforded by Article 2, the Court must subject complaints about deprivations of life to the most careful scrutiny, taking into consideration all relevant circumstances. Persons in custody are in a vulnerable position and the authorities are under an obligation to account for their treatment. Consequently, where an individual is taken into police custody in good health but later dies, it is incumbent on the State to provide a plausible explanation of the events leading to his death (see, mutatis mutandis, Selmouni v. France [GC], no. 25803/94, § 87, ECHR 1999-V, and Salman and Velikova, cited above). 111. In assessing evidence, the Court adopts the standard of proof “beyond reasonable doubt” (see Ireland v. the United Kingdom, judgment of 18 January 1978, Series A no. 25, pp. 64-65, § 161). However, such proof may follow from the co-existence of sufficiently strong, clear and concordant inferences or of similar unrebutted presumptions of fact. Where the events in issue lie wholly, or in large part, within the exclusive knowledge of the authorities, as in the case of persons within their control in custody, strong presumptions of fact will arise in respect of injuries and death occurring during that detention. Indeed, the burden of proof may be regarded as resting on the authorities to provide a satisfactory and convincing explanation (see Salman, cited above, § 100).