DRAGOJEVIĆ v. CROATIA JUDGMENT 19 6. Member states should ensure that competent authorities apply less intrusive investigation methods than special investigation techniques if such methods enable the offence to be detected, prevented or prosecuted with adequate effectiveness. 7. Member states should, in principle, take appropriate legislative measures to permit the production of evidence gained from the use of special investigation techniques before courts. Procedural rules governing the production and admissibility of such evidence shall safeguard the rights of the accused to a fair trial.” 63. Article 23 of the Council of Europe’s Criminal Law Convention on Corruption (ETS no. 173, 27 January 1999) provides that each party is to adopt such legislative and other measures as may be necessary, including those permitting the use of special investigative techniques, to enable it to facilitate the gathering of evidence in this sphere. The explanatory report on the Convention further specifies that “special investigative techniques” may include the use of undercover agents, wiretapping, interception of telecommunications and access to computer systems. Article 35 states that the Convention does not affect the rights and undertakings deriving from international multilateral conventions concerning special matters. 64. Article 4 of the Council of Europe’s Convention on Laundering, Search, Seizure and Confiscation of the Proceeds from Crime (ETS no. 141, 8 November 1990) provides that each party should consider adopting such legislative and other measures as may be necessary to enable it to use special investigative techniques facilitating the identification and tracing of proceeds and the gathering of evidence related thereto. 65. The use of special investigative techniques, such as controlled deliveries in the context of illicit trafficking in narcotic drugs, is also provided for in Article 73 of the Convention implementing the Schengen Agreement of 14 June 1985 on the gradual abolition of checks at the common borders, signed in Schengen on 19 June 1990. 66. The use of special investigative techniques, including electronic or other forms of surveillance and undercover operations, is also envisaged in Article 20 of the United Nations Convention against Transnational Organized Crime (A/RES/55/25) of 8 January 2001. THE LAW I. ALLEGED VIOLATION OF ARTICLE 8 OF THE CONVENTION 67. The applicant complained that the secret surveillance of his telephone conversations had been in violation of the guarantees of Article 8 of the Convention, which reads as follows: