R (on the application of BF (Eritrea)) v Secretary of State for the Home Department

The Supreme Court allowed the Secretary of State's appeal and held that the policy guidance known as criterion C governing initial age assessments by immigration officers was lawful. The court applied the principle from Gillick that a policy must not direct addressees to act contrary to their legal duties and concluded that criterion C did not do so. The court treated the statutory distinction between children and adults (notably section 55 of the Borders, Citizenship and Immigration Act 2009 and the amendments to Schedule 2 of the Immigration Act 1971 introducing paragraph 18B) as a legitimate rule to be applied by immigration officers on the basis of the available evidence. It rejected the Court of Appeal's test that policy is unlawful if it creates a real risk of more than a minimal number of children being detained or could be improved to avoid that risk, finding that neither Gillick nor UNISON supported imposing on the Secretary of State a duty to eliminate all risk of misclassification. The court emphasised the built‑in safeguards in the guidance (benefit of the doubt, requirement of senior second opinion and review on receipt of new evidence) and that errors by officers are to be addressed by individual remedies rather than by requiring the Secretary of State to displace the statutory rule.

Background and facts:

• The respondent BF, an Eritrean national, entered the United Kingdom on 11 March 2014 and claimed asylum as an unaccompanied child claiming a birth date of 15 February 1998. Immigration officers initially assessed him, applying Home Office policy criterion C, as significantly over 18, and he was treated as an adult and detained on several occasions while removal to Italy was pursued under the Dublin III Regulation (Regulation (EU) No 604/2013). Later Merton-compliant age assessments were conducted, with differing results; a later independent assessment supported BF's claimed age and BF pursued related proceedings for wrongful detention.

Procedural posture:

• BF sought judicial review to quash criterion C of the Home Office guidance on the grounds that it permitted or risked unlawful treatment of children by enabling detaining persons who were in fact children. The Upper Tribunal (Judge Storey) dismissed the claim on 31 July 2017. The Court of Appeal ([2019] EWCA Civ 872) allowed BF's appeal and held criterion C unlawful (with majority disagreement on the post‑2014 versions). The Secretary of State appealed to the Supreme Court. The Equality and Human Rights Commission intervened.

Nature of the application and issues:

• BF sought quashing of criterion C in the Home Office guidance which allowed immigration officers, in the absence of documentary evidence, to assess a claimant as an adult where their physical appearance and demeanour "very strongly suggests" they are significantly over 18. The principal issues were (i) what legal test governs review of policy guidance (including the relevance of Gillick and UNISON), and (ii) whether criterion C, in context, was unlawful because it created a real risk that children would be treated and detained as adults.

Court's reasoning and subsidiary findings:

• The court set out that the principal obligation on a policy‑maker is the narrow Gillick obligation not to direct addressees to act unlawfully and that this does not impose a broader common law duty to craft policy so as to eliminate all realistic risks of subordinate error. The court accepted as common ground the legal effect of Ali (that age is a matter of precedent fact and detention of a person who is in fact a child as an adult will be unlawful even if officers reasonably believed them to be an adult) but held that this does not require the Secretary of State to reformulate the statutory rule itself.
• The Supreme Court rejected the Court of Appeal's test that policy is unlawful if it creates a real risk of more than a minimal number of children being unlawfully detained or could be improved to avoid that risk. It held UNISON inapposite because that line of authority addresses impediments to court access, not the present policy context. The court also rejected submissions that section 55 or Convention rights required the Secretary of State to prescribe a much wider margin of error (for example, treating only those who appear 23 or 25 or older as adults).
• The court concluded that criterion C, as formulated and read with the broader guidance (including benefit of the doubt, requirement for a countersigning senior officer and review on new evidence), did not instruct officers to act contrary to their legal duties and was therefore lawful. The Secretary of State had complied with the section 55 duty and the policy contained safeguards designed to minimise risk of unlawful detention of children.

Wider context:

• The court noted the practical difficulty and unreliability of assessing age by appearance and demeanour and that Merton assessments by local authorities are the more reliable method, but emphasised that initial decisions by immigration officers must be taken on available evidence and are subject to subsequent review and challenge.

Appeal allowed. The Supreme Court held that the relevant policy guidance, in particular criterion C, was lawful. The court concluded that the correct legal test was the Gillick principle (the policy must not direct recipients to act contrary to their legal duties) and that neither UNISON nor the Court of Appeal’s "real risk" test required the Secretary of State to specify a wider margin of error (such as treating only those who appear 23/25 or older as adults). The guidance, read with safeguards (benefit of the doubt, second senior officer assessment, review on new evidence), did not direct officers to act unlawfully and complied with the section 55 duty.

Permission to seek judicial review was granted in October 2016. The Upper Tribunal (Judge Storey) dismissed BF's challenge (judgment 31 July 2017). The Court of Appeal allowed BF's appeal ([2019] EWCA Civ 872). The Secretary of State appealed to the Supreme Court, which allowed the appeal ([2021] UKSC 38).