87. The Court reiterates that in order for an arrest on reasonable suspicion to be justified under Article 5 § 1 (c), it is not necessary for the police to have obtained sufficient evidence to bring charges, either at the point of arrest or while the applicant is in custody (see Brogan and Others v. the United Kingdom, 29 November 1988, § 53, Series A no. 145‑B). Nor is it necessary that the person detained should ultimately have been charged or taken before a court. The object of detention for questioning is to further a criminal investigation by confirming or discontinuing suspicions which provide the grounds for detention. Thus, facts which raise a suspicion need not be of the same level as those necessary to justify a conviction or even the bringing of a charge, which comes at the next stage of the process of criminal investigation (see Murray v. the United Kingdom, 28 October 1994, § 55, Series A no. 300‑A).
88. However, the requirement that the suspicion must be based on reasonable grounds forms an essential part of the safeguard against arbitrary arrest and detention. The fact that a suspicion is held in good faith is insufficient. The words “reasonable suspicion” mean the existence of facts or information which would satisfy an objective observer that the person concerned may have committed the offence. What may be regarded as “reasonable” will depend upon all the circumstances (see Fox, Campbell and Hartley v. the United Kingdom, 30 August 1990, § 32, Series A no. 182). The length of the deprivation of liberty may also be material to the level of suspicion required (see Murray, cited above, § 56).
89. When assessing the “reasonableness” of the suspicion, the Court must be enabled to ascertain whether the essence of the safeguard afforded by Article 5 § 1 (c) has been secured. Consequently, the respondent Government have to furnish at least some facts or information capable of satisfying the Court that the arrested person was reasonably suspected of having committed the alleged offence (see Fox, Campbell and Hartley, cited above, § 34 in fine).
90. The Court notes that the applicant in the present case complained of the lack of “reasonable” suspicion against him throughout the entire period of his detention, including both the initial period following his arrest and the subsequent periods when his remand in custody had been authorised and extended by court orders. In this connection, the Court reiterates that the persistence of reasonable suspicion that the person arrested has committed an offence is a prerequisite for the lawfulness of the continued detention (see, among many other authorities, Stögmüller v. Austria, 10 November 1969, p. 40, § 4, Series A no. 9, and McKay v. the United Kingdom [GC], no. 543/03, § 44, ECHR 2006‑X). Accordingly, while reasonable suspicion must exist at the time of the arrest and initial detention, it must also be shown, in cases of prolonged detention, that the suspicion persisted and remained “reasonable” throughout the detention.