Judgment Approved by the court for handing down. “93. ... foreseeability in the special context of secret measures of surveillance, such as the interception of communications, cannot mean that an individual should be able to foresee when the authorities are likely to intercept his communications so that he can adapt his conduct accordingly (see, inter alia, Leander v. Sweden, judgment of 26 August 1987, Series A no. 116], p. 23, § 51). However, especially where a power vested in the executive is exercised in secret, the risks of arbitrariness are evident (see, inter alia, Malone, cited above, p. 32, § 67; Huvig, cited above, pp. 54-55, § 29; and Rotaru). It is therefore essential to have clear, detailed rules on interception of telephone conversations, especially as the technology available for use is continually becoming more sophisticated (see Kopp v. Switzerland, judgment of 25 March 1998, Reports 1998-II, pp. 542-43, § 72, and Valenzuela Contreras v. Spain, judgment of 30 July 1998, Reports 1998-V, pp. 1924-25, § 46). The domestic law must be sufficiently clear in its terms to give citizens an adequate indication as to the circumstances in which and the conditions on which public authorities are empowered to resort to any such measures (see Malone, ibid.; Kopp, cited above, p. 541, § 64; Huvig, cited above, pp. 54-55, § 29; and Valenzuela Contreras, ibid.). 94. Moreover, since the implementation in practice of measures of secret surveillance of communications is not open to scrutiny by the individuals concerned or the public at large, it would be contrary to the rule of law for the legal discretion granted to the executive or to a judge to be expressed in terms of an unfettered power. Consequently, the law must indicate the scope of any such discretion conferred on the competent authorities and the manner of its exercise with sufficient clarity to give the individual adequate protection against arbitrary interference (see, among other authorities, Malone, cited above, pp. 32-33, § 68; Leander, cited above, p. 23, § 51; and Huvig, cited above, pp. 54-55, § 29). 95. In its case-law on secret measures of surveillance, the Court has developed the following minimum safeguards that should be set out in statute law in order to avoid abuses of power: the nature of the offences which may give rise to an interception order; a definition of the categories of people liable to have their telephones tapped; a limit on the duration of telephone tapping; the procedure to be followed for examining, using and storing the data obtained; the precautions to be taken when communicating the data to other parties; and the circumstances in which recordings may or must be erased Davis & Ors v SSHD