By Peter Mant K.C. and Nicola Kohn, 14th November 2025
This post picks up on concerns raised by some observers of the AG for Northern Ireland’s reference[1] case who “don’t think the judges have the requisite knowledge base to understand what’s at stake” (see When open justice undermines public confidence: Scrutinising the Supreme Court).
The Supreme Court hears cases from across the United Kingdom on a vast array of different topics. The former President, Baroness Hale, had a unique insight into mental health and capacity law because of her academic background and experience as a judge of the Family Division. It is, perhaps, unfortunate that none of the current Justices have experience of sitting in the Family Division in England.[2] However, what is inevitable is that, in many cases before the Supreme Court, the Justices will not have the same intimate subject-matter knowledge as specialist lawyers and other professionals interested in the outcome. It is the role of the advocates to explain the necessary background – and in this case some of the leading advocates in the field of mental capacity law were instructed to present the arguments.
What made this case particularly difficult was the absence of a factual matrix against which to test and present those arguments. The vast majority of cases before the Supreme Court are decided on facts determined by a first instance judge. In other contexts, the courts have emphasised the importance of developing the law “on the basis of actual facts found at trial not on hypothetical facts assumed (possibly wrongly) to be true”.[3]
References on a point of law are a product of devolution. Under the Northern Ireland Act 1998,[4] and equivalent Scottish and Welsh legislation,[5] the relevant Law Officer may refer a “devolution issue” which is not the subject of proceedings directly to the Supreme Court. However, even in this context, the Supreme Court has said that “it is desirable that legal questions be determined against the background of a clear factual matrix, rather than as theoretical or academic issues of law”. It recently declined to determine a Northern Irish reference where the same issue arose in pending proceedings.[6]
“Devolution issues” include questions of whether a proposed exercise of a function by a Northern Ireland department would be invalid because it would be incompatible with Convention rights.[7] The question referred to the Supreme Court by the Attorney General for Northern Ireland was whether proposed revisions to the DoLS Code of Practice in respect of consent would be incompatible with Article 5.
It is understandable that the Attorney General for Northern Ireland would want the Supreme Court to determine this question before implementing the proposed revisions. Those revisions (a) conflict with the unchallenged assumption in Cheshire West that a person who lacks mental capacity cannot consent to arrangements that objectively amount to a deprivation of liberty; and (b) remove from the procedural protections of Article 5 the very people who are affected by the revisions (thus inhibiting the practical ability of those people to bring an effective challenge to the new regime).
However, many of the hypothetical arguments and postulated facts raised at the hearing concerned not the issue of consent on which the Attorney General sought guidance, but the wider issue of whether Cheshire West was correctly decided viz. the “acid test”. [8] That question was raised late in the day by the Secretary of State for Health and Social Care who does not have standing to refer cases directly to the Supreme Court himself and who could, at least arguably, have pursued the issue by intervention in a substantive case before the Court of Protection.
It remains to be seen whether the Justices will take up the Secretary of State’s invitation to revise the “acid test”.
Peter Mant K.C. and Nicola Kohn, both of 39 Essex Chambers were instructed (with Sarah Westoby of Leigh Day) on behalf of the AIRE Centre to intervene in this case: permission to intervene was refused by the Supreme Court. Peter acted for the local authorities in Cheshire West.
[1] A Reference by the Attorney General for Northern Ireland of a devolution issue under paragraph 34 of Schedule 10 to the Northern Ireland Act 1998 UKSC/0042
[2] Save for Lord Stephens who sat in the Family Division in Northern Ireland from 2008 to 2014.
[3] Barrett v Enfield [2001] 2 AC 550
[4] Schedule 10, para 34
[5] Scotland Act 1998, Schedule 6, para 34; Government of Wales Act 2006, Schedule 9, para
[6] Attorney General for Northern Ireland’s Reference [2019] UKSC 1
[7] See section 24 and schedule 10, para 1
[8] The so-called “acid test” is found at para 54 of Cheshire West: a person is deprived of their liberty if they are “under complete supervision and control… and… [are] not free to leave the place where [they] live…”
Promoting Open Justice in the Court of Protection 