28 EL HASKI v. BELGIUM JUDGMENT ECHR 2003-VII) that the need to combat terrorism could not justify a restriction on the very essence of the rights of the defence. This had also been the approach adopted by the Spanish Supreme Court in its judgment of 20 July 2006, reversing the conviction of Hamed Abderrahaman Ahmed on the ground that, because of the disrespect for the fundamental rights of the Guantánamo detainees and for due process safeguards, any act carried out in the Guantánamo context had to be declared completely invalid and as such inexistent. They observed that, similarly, the 2009 report of the Eminent Jurists Panel on Terrorism, Counter-terrorism and Human Rights had expressed concern that, due to the international dimension of recent terrorism attacks, there had been cases where the prosecution had sought to rely on statements of the accused or witnesses obtained abroad under conditions that cast doubt on their reliability. They emphasised that the prevention of torture or other ill-treatment of detainees could only be effectively safeguarded if the judiciary responded urgently and effectively when any allegations concerning such ill-treatment were brought to their attention. C. The Court’s assessment ... 2. Merits (a) General principles 81. The Court reiterates that its duty, pursuant to Article 19 of the Convention, is to ensure the observance of the engagements undertaken by the Contracting States to the Convention. In particular, it is not its function to deal with errors of fact or of law allegedly committed by a national court unless and in so far as they may have infringed rights and freedoms protected by the Convention. While Article 6 guarantees the right to a fair hearing, it does not lay down any rules on the admissibility of evidence as such, which is primarily a matter for regulation under national law (see, among other authorities, Schenk v. Switzerland, 12 July 1988, §§ 45-46, Series A no. 140; Teixeira de Castro v. Portugal, 9 June 1998, § 34, Reports of Judgments and Decisions 1998-IV; Heglas v. the Czech Republic, no. 5935/02, § 84, 1 March 2007; and Gäfgen v. Germany [GC], no. 22978/05, § 162, ECHR 2010). 82. It is not, therefore, the role of the Court to determine, as a matter of principle, whether particular types of evidence – for example, evidence obtained unlawfully in terms of domestic law – may be admissible. The question which must be answered is whether the proceedings as a whole, including the way in which the evidence was obtained, were fair. This involves an examination of the unlawfulness in question and, where the