9.11.2017 A & Ors v Secretary of State for the Home Department [2004] EWCA Civ 1123 (11 August 2004) facts with which they may interact. The question of whether the risk to national security is sufficient to justify the appellant's deportation cannot be answered by taking each allegation seriatim and deciding whether it has been established to some standard of proof. It is a question of evaluation and judgment, in which it is necessary to take into account not only the degree of probability of prejudice to national security but also the importance of the security interest at stake and the serious consequences of deportation for the deportee." 229. I will first address Mr Gill's submission that where past facts are relied on by the Secretary of State to establish a reasonable suspicion that an individual is a terrorist within s.21, then on an appeal to SIAC the Secretary of State must prove the facts alleged "to a high degree of probability or at least on balance of probabilities". The starting-point must be the language of the statute. It seems to me that the structure of s.21(1) repays close attention. Two states of mind are required of the Secretary of State if he is to issue a lawful certificate: a reasonable belief in a risk and a reasonable suspicion of a fact. Belief and suspicion are not the same, though both are less than knowledge. Belief is a state of mind by which the person in question thinks that X is the case. Suspicion is a state of mind by which the person in question thinks that X may be the case. Now, the risk to national security referred to in s.21(1)(a) is a matter of evaluation; the Secretary of State must reasonably believe that the risk is correctly evaluated. But when in s.21(1)(b) the statute confronts fact rather than evaluation, a lesser state of mind is required; the Secretary of State must reasonably suspect that A is a terrorist, that is, he must reasonably think that A may be a terrorist. This alignment of belief with evaluation and `suspicion with fact, which is plainly carried through to the appeal provision contained in s.25, must have been arrived at advisedly. No doubt it was driven by the nature of the subject-matter. The assessment of the question whether a person is a terrorist within the meaning of s.21(2) will most likely depend on intelligence – the pieces of an often incomplete jigsaw puzzle – rather than hard evidence. Accordingly it will be difficult or impossible to get any further than suspicion. 230. These considerations possess, in my judgment, two consequences for Mr Gill's argument. First, while it would have been hard enough to find a requirement of proof of facts had the statute said in s.21(1) (b) "believes that the person is a terrorist", it is certainly impossible to do so faced with a requirement of suspicion only. Mr Gill's submission is hopelessly foundered on the language of the Act. As for his reliance on Rehman, it is important to have in mind with respect that Rehman did not at all engage Part IV of ATCSA, which was not on the statute book at the time of the Secretary of State's decision or SIAC's judgment on appeal in that case. Their Lordships were dealing with the deportation provisions contained in the Immigration Act 1971 which have no analogue to ATCSA s.21. Moreover, while I of course acknowledge Lord Slynn's reference (paragraph 22) to the need to prove specific past acts relied on, the central place of evaluation in a security context received much emphasis from their Lordships. 231. The second impact upon Mr Gill's argument arising from these considerations of the choice of language in the Act is this. The nature of the subject-matter is such that it will as I have indicated very often, usually, be impossible to prove the past facts which make the case that A is a terrorist. Accordingly a requirement of proof will frustrate the policy and objects of the Act. Now, it will at once be obvious that the derogation issue and the scrutiny issue run together here. In dealing with the former I have already said that the legislature's choice of belief and suspicion as the test for certification and thus detention tends to support the view that the target of the Act's policy includes those who belong to loose, amorphous, unorganised groups. So it does; the choice is apt to strike the target. Proof would not be. Just as Mr Gill's submission misdescribes the Act's policy and objects, so it misdescribes the mechanisms provided for their achievement. 232. However in addressing the derogation issue I also said that the imperative of a solid justification, on the words of the statute, for any claimed power of executive detention on grounds only of suspicion and belief engages the scrutiny issue; and I have summarised Mr Gill's various formulations of the need for stringent tests before the material belief or suspicion should be held to be established. Should our abhorrence of executive detention drive the court to accept that in truth something more than belief and suspicion is required, despite the statute's language and its aptness to achieve the statute's objects? http://www.bailii.org/ew/cases/EWCA/Civ/2004/1123.html 58/113