TEIXEIRA DE CASTRO JUDGMENT OF 9 JUNE 1998 10 national courts to assess the evidence before them. The Court's task under the Convention is not to give a ruling as to whether statements of witnesses were properly admitted as evidence, but rather to ascertain whether the proceedings as a whole, including the way in which evidence was taken, were fair (see, inter alia, the Van Mechelen and Others v. the Netherlands judgment of 23 April 1997, Reports of Judgments and Decisions 1997-III, p. 711, § 50). 35. More particularly, the Convention does not preclude reliance, at the investigation stage of criminal proceedings and where the nature of the offence so warrants, on sources such as anonymous informants. However, the subsequent use of their statements by the court of trial to found a conviction is a different matter (see, mutatis mutandis, the Kostovski v. the Netherlands judgment of 20 November 1989, Series A no. 166, p. 21, § 44). 36. The use of undercover agents must be restricted and safeguards put in place even in cases concerning the fight against drug trafficking. While the rise in organised crime undoubtedly requires that appropriate measures be taken, the right to a fair administration of justice nevertheless holds such a prominent place (see the Delcourt v. Belgium judgment of 17 January 1970, Series A no. 11, p. 15, § 25) that it cannot be sacrificed for the sake of expedience. The general requirements of fairness embodied in Article 6 apply to proceedings concerning all types of criminal offence, from the most straightforward to the most complex. The public interest cannot justify the use of evidence obtained as a result of police incitement. 37. The Court notes, firstly, that the present dispute is distinguishable from the case of Lüdi v. Switzerland (see the judgment of 15 June 1992, Series A no. 238), in which the police officer concerned had been sworn in, the investigating judge had not been unaware of his mission and the Swiss authorities, informed by the German police, had opened a preliminary investigation. The police officers’ role had been confined to acting as an undercover agent. 38. In the instant case it is necessary to determine whether or not the two police officers’ activity went beyond that of undercover agents. The Court notes that the Government have not contended that the officers’ intervention took place as part of an anti-drug-trafficking operation ordered and supervised by a judge. It does not appear either that the competent authorities had good reason to suspect that Mr Teixeira de Castro was a drug trafficker; on the contrary, he had no criminal record and no preliminary investigation concerning him had been opened. Indeed, he was not known to the police officers, who only came into contact with him through the intermediary of V.S. and F.O. (see paragraph 10 above). Furthermore, the drugs were not at the applicant’s home; he obtained them from a third party who had in turn obtained them from another person (see paragraph 11 above). Nor does the Supreme Court’s judgment of 5 May 1994 indicate that, at the time of his arrest, the applicant had more drugs in his possession than the quantity the police officers had requested thereby going beyond what he had been incited to do by the police. There is no