For civil practitioners, the White Book is an (inordinately expensive) but often indispensable addition to their suite of materials. It is also frequently cited by the courts. It is unfortunate, therefore, that the 2023 edition does not quite get it right in relation to litigation capacity (separately, there is much bigger issue, for which the White Book editors can bear no responsibility, as to whether Part 21 gets it right at all in terms of the approach to take to litigation capacity).
In particular, the following paragraph (2.1.03) of the White Book contains an error I hope can be corrected in future editions:
In legal proceedings the burden of proof is on the person who asserts that capacity is lacking. If there is any doubt as to whether a person lacks capacity, this is to be decided on the balance of probabilities; see s.2(4) of the 2005 Act. The presumption of capacity will only be displaced on the basis of proper evidence. That evidence must be current and must deal first with the “diagnostic test” of impairment or disturbance of the functioning of the mind or brain, then secondly the “functional test” of whether the impairment renders the person unable to make the relevant decisions in litigation. It must deal with all the factors in s.3 of the Mental Capacity Act including whether there are any practical steps which could be taken to assist the claimant in making decisions in relation to the litigation. See Fox v Wiggins  EWHC 2713 (QB) and King v Wright Roofing Co Ltd  EWHC 2129 (QB).
The error, in the sentence in bold, is to follow the ‘old’ ordering as set out in the Mental Capacity Act Code of Practice. However, in A Local Authority v JB  UKSC 52, the Supreme Court made clear that the test need to be applied in the reverse order. Following the Court of Appeal in York City Council v C  EWCA Civ 478 (sometimes also called PC v NC), Lord Stephens identified that section 2(1) – the core determinative provision – requires the court (and hence anyone else, outside court) to address two questions. First, is the person unable to make the decision for themselves? As Lord Stephens noted:
67. […] The focus is on the capacity to make a specific decision so that the determination of capacity under Part 1 of the MCA 2005 is decision-specific as the Court of Appeal stated in this case at para 91. The only statutory test is in relation to the ability to decide. In the context of sexual relations, the other vocabulary that has developed around the MCA, of “person-specific”, “act-specific”, “situation-specific” and “issue-specific”, should not be permitted to detract from that statutory test, though it may helpfully be used to identify a particular feature of the matter in respect of which a decision is to be made in an individual case.
68. As the assessment of capacity is decision-specific, the court is required to identify the correct formulation of “the matter” in respect of which it must evaluate whether P is unable to make a decision for himself: see York City Council v C at paras 19, 35 and 40.
69. The correct formulation of “the matter” then leads to a requirement to identify “the information relevant to the decision” under section 3(1)(a) which includes information about the reasonably foreseeable consequences of deciding one way or another or of failing to make the decision: see section 3(4).
If the court concludes that P cannot make the decision, then the second question is whether there is a “clear causative nexus between P’s inability to make a decision for himself in relation to the matter and an impairment of, or a disturbance in the functioning of, P’s mind or brain.” Lord Stephens was clear (at paragraph 78) that the two questions in s.2(1) were to be approached in the sequence set out above, i.e. starting with the functional aspect. Whilst the Supreme Court was considering the MCA in the context of its application by the Court of Protection, Lord Stephens’ observations apply with equal force to its application by the civil courts, because CPR r.21.1(2)(c) expressly provides that references to a person lacking capacity are references to a person lacking capacity for those purposes applying the MCA 2005 (see also Saulle v Nouvet  EWHC 2902 (QB).) Helpfully, the recently revised certificate as to capacity to conduct proceedings has the test the right way around.
Separately, it is unfortunate that in the same highlighted sentence, the White Book uses the term ‘diagnostic’ element. Although in common currency, it is misleading. As we put it in our guidance note on capacity:
As a judge has put it, a formal diagnosis “may constitute powerful evidence informing the answer to the second cardinal element of the single test of capacity, namely whether any inability of [P] to make a decision in relation to the matter in issue is because of an impairment of, or a disturbance, in the functioning of the mind or brain” [see North Bristol NHS Trust v R  EWCOP 5 at paragraph 48]. However, it is entirely legitimate to reach such a conclusion in the absence either of a formal diagnosis or without being able to formulate precisely the underlying condition or conditions. To this extent, therefore, the term “diagnostic” test which is often used here is misleading.
Using the term ‘diagnostic element’ also suggests that medical evidence is required, but this is incorrect. The White Book (in the same paragraph, 21.0.3) notes that Hinduja v Hinduja  EWHC 1533 (Ch) as an example of a case where medical evidence is not necessary, this is perhaps rather to understate the position. Falk J (as she then was) undertook a first principles analysis of the position, identifying that medical evidence is simply not required by the Rules.
37. There is no requirement in the [Civil Procedure Rules] to provide medical evidence. The absence of any such requirement was commented on by Chadwick LJ in Masterman-Lister at . There is no reference to medical evidence in CPR 21.6. The only reference to medical evidence is in paragraph 2.2 of PD 21, which applies where CPR 21.5(3) is being relied on. That requires the grounds of belief of lack of capacity to be stated and, “if” that belief is based on medical opinion, for “any relevant document” to be attached. So the Practice Direction provides that medical evidence of lack of capacity must be attached only if (a) it is the basis of the belief, and (b) exists in documentary form. It does not require a document to be created for the purpose.
50. In summary, medical evidence is not required under the rules […]
Whilst Practice Direction 21 has now been removed, the reference to medical opinion (or, now, ‘expert opinion’) is to be found in CPR r.21.6, and is on the same basis. There may well be situations in which the court will consider that it cannot make a determination that the party lacks capacity to conduct the proceedings absent medical evidence. However, I would suggest that it is important that representatives and judges approach matters from the correct starting position (not least because it also opens the door to taking the same approach as is now taken in the Court of Protection, namely that where expertise is, in fact, required, that expertise can be obtained from an appropriately qualified professional such as a social worker who is able to speak to the individual’s capacity.