Part 3 71 3.1 Arrest and Detention of Suspects The protection of physical liberty and freedom from arbitrary arrest or detention are fundamental characteristics of democratic societies. Arbitrary arrest or detention is prohibited under international human rights law. It may also generate popular support for organizations suspected of terrorism, making the job of the police increasingly difficult. Indeed, arbitrary arrest or detention is often an overreaction by the state that terrorists seek to provoke. Any arrest or detention of a terrorism suspect must have a legal basis that is pre-existent to the commission of the offence. It must also be justified on specific grounds, either by an evidential threshold that he or she has committed a terrorist offence or is about to commit one, or for the purposes of deportation or extradition.68 In the former case, the arrest or detention would allow the police to gather evidence without the suspect’s interference in the process. The evidential threshold set by the ECtHR – reasonable suspicion – is helpful in this regard.69 The reasonable suspicion threshold is met when an objective observer would be satisfied that the person concerned may have committed the offence.70 This is more than just an honestly held belief that someone is guilty, but it is not as strong as being sufficient to prove beyond any doubt in a court that the suspect has committed a crime. The mere existence of previous convictions for terrorism-related offences cannot, for instance, constitute reasonable suspicion in the eyes of an objective observer and, therefore, cannot be considered as sufficient to arrest and detain a person. In case of arrest or detention on reasonable suspicion that the suspect has committed or is about to commit a terrorism-related offence, such arrest or detention should aim at bringing the detainee before a court. The prompt appearance of the terrorism suspect before a judge or a judicial authority to determine the lawfulness and necessity of the detention is a crucial safeguard against arbitrary arrest and detention. It should happen immediately 68 These two reasons are particularly relevant in the context of a counter-terrorism investigation. Additional legitimate reasons to deprive someone of his liberty can be found in Article 5 of the ECHR. 69 ECtHR judgments, op. cit., note 47. 70 ECtHR, Fox, Campbell and Hartley v. UK, Application Nos. 12244/86, 12245/86 and 12383/86, 30 August 1990, para. 32, <http://hudoc.echr.coe.int/sites/eng/pages/search. aspx?i=001–57721>.