ELCI AND OTHERS v. TURKEY JUDGMENT 108 B. The Court's assessment 667. The Court recalls that Article 5 § 1 of the Convention requires that any deprivation of liberty must be both “lawful” and comply with “a procedure prescribed by law”. By the use of these terms the Convention refers back essentially to national law and lays down the obligation to conform to the substantive and procedural rules thereof. However, it requires in addition that any deprivation of liberty should be consistent with the purpose of Article 5, namely to protect individuals from arbitrariness (see, in particular, the Winterwerp v. the Netherlands judgment of 24 October 1979, Series A no. 33, pp. 17-18 and 19-20, §§ 39 and 45, and the van der Leer v. the Netherlands judgment of 21 February 1990, Series A no. 170, p. 12, § 22). 668. The Court further recalls that the requirement in paragraph 1 (c) of Article 5 that there should exist a “reasonable suspicion” against the person who is deprived of his liberty presupposes the existence of facts or information which would satisfy an objective observer that the person concerned may have committed the offence in question. What may be regarded as “reasonable” will however depend on all the circumstances (See the Fox, Campbell and Hartley v. the United Kingdom judgment of 30 August 1990, Series A no.182, p. 16, § 32). 669. The Court would emphasise the central role of the legal profession in the administration of justice and the maintenance of the rule of law. The freedom of lawyers to practise their profession without undue hindrance is an essential component of a democratic society and a necessary prerequisite for the effective enforcement of the provisions of the Convention, in particular the guarantees of fair trial and the right to personal security. Persecution or harassment of members of the legal profession thus strikes at the very heart of the Convention system. For this reason, allegations of such persecution in whatever form, but particularly large scale arrests and detention of lawyers and searching of lawyers' offices, will be subject to especially strict scrutiny by the Court. 670. The Government claim that in the present case each of the applicants was lawfully detained on reasonable suspicion of having committed criminal offences under Articles 168 and 169 of the Turkish Criminal Code. 671. As to the reasonableness of the suspicion against the applicants, the Court observes that Abdülhakim Güven, a PKK confessor, denounced to the gendarmerie all the applicants, with the exception of Arif Altinkalem, for assisting the PKK, in particular by acting as couriers between their imprisoned clients and other PKK members (paragraphs 424-434 above). As a result, between 15 November and 7 December 1993, the applicants were taken into custody by the police or gendarmes and detained at the Diyarbakır provincial gendarmerie command for periods varying from 7 to