did the arresting officer honestly suspect that the person arrested was guilty of the offence;
if so, were there reasonable grounds for that suspicion;
if so, was the discretionary power of arrest exercised lawfully in accordance with public law principles;
see Castorina v Chief Constable of Surrey13. It should be noted that the third of these issues, when raised, involves the Court considering public law doctrines, such as whether the decision to arrest was unreasonable in the Wednesbury sense or whether the decision was made for an improper purpose14.
9.The tort can be relied upon in relation to any detention of a person by a public authority (or private individual), save for detention pursuant to a Court order, unless the order is made without jurisdiction15. Claims may arise, for example, from detention by immigration authorities or in purported pursuance of powers under the Mental Health Act 1983 9”MHA”), in addition to detention in police custody.
10.In D v Home Office16 the defendant sought to strike out and / or obtain summary judgment in relation to County Court claims seeking a declaration that the Home Office had acted incompatibly with the claimants’ rights under articles 2, 3, 5 and 8 ECHR and damages pursuant to the HRA and for false imprisonment. The claimants were asylum seekers who were detained in purported pursuance of immigration officers’ powers under schedule 2 of the Immigration Act 1971. The claimants alleged that their various periods of detention were unlawful because the decisions to detain were: unreasonable and / or disproportionate and / or failed to follow applicable internal policy and / or failed to safeguard or protect the interests of the children of the family as required by the UN Convention on the Rights of the
13 (1988) 138 NLJ Rep 180 CA. The arrest may also be unlawful if the person arrested is not told that he is under arrest and the grounds of the same, either at the time of arrest or as soon as practicable thereafter, see section 28 PACE.
14 For example see Plange v Chief Constable of Humberside (1992) The Times 23 March. The Court’s approach in this regard has not changed as a result of the HRA, save that in considering whether the discretion was exercised lawfully, the Court will bear in mind the importance of the right to liberty protected by ECHR article 5: Cumming v Chief Constable of Northumbria  EWCA Civ 1844.
15 For details of the principles regarding detention pursuant to judicial acts see Clerk & Lindsell on Torts (19th ed) paras 15-41 – 15-48.
16  1 WLR 1003 CA.