Capacity to engage in sexual relations: the relevance of the partner’s consent

26 November 2021 by

A Local Authority (Respondent) v JB (by his Litigation Friend, the Official Solicitor) (Appellant) – UKSC 2020/0133 Court of Appeal (Civil Division)

The Supreme Court has upheld the Court of Appeal’s decision that to have capacity to engage in sexual relations, a person needs to be able to understand that their sexual partner must have the capacity to consent to the sexual activity and must, in fact, consent before and during the sexual activity.

The appellant, JB, is a 37 year-old single man with a complex diagnosis of autistic spectrum disorder combined with impaired cognition. He has a complex diagnosis of autistic spectrum disorder (Asperger’s syndrome) combined with impaired cognition as a result of suffering significant brain damage from epilepsy.

JB has expressed a strong desire to have a girlfriend and engage in sexual relations. Part of JB’s diagnosis of Asperger’s syndrome caused him to be

…obsessionally fixated on a particular woman, sending inappropriate sexual messages, inappropriate touching, and targeting the vulnerable

His previous behaviour towards women has led the respondent local authority to conclude that he cannot safely have unsupervised contact with them. JB had argued in the Court of that he had capacity to consent to sexual relations in circumstances where the expert evidence had found that JB understood the mechanics of sexual acts and the risks of pregnancy and sexually transmitted disease but that his ‘understanding of consent’ was lacking.

The outcome for JB, if he was found to lack capacity to make decisions in respect of sexual relations, would be that he would be deprived of all sexual relations and that no other person could consent on his behalf (S27(1)(b) Mental Capacity Act 2005(MCA).

JB was successful at first instance in the Court of Protection, but the Court of Appeal reversed the decision and found in favour of the Local Authority. On further appeal to the Supreme Court the court agreed with the Court of Appeal the result being that JB did, in fact, lack capacity.

Proceedings in the Court of Protection

In the Court of Protection, the judge held that the consent of others was not relevant to the question of whether JB had the capacity to consent to sexual relations and granted a declaration that JB has the capacity to consent to sexual relations. The Local Authority were concerned, however, that if JB did not understand that the other person needed to be capable of consenting to sexual relations then there was a risk of sexual offences being committed by JB and harm would be caused to third parties.

The Local Authority appealed to the Court of Appeal.

Court of Appeal

Permission to appeal was granted and the full appeal was heard on 3 March 2020 by Sir Andrew McFarlane, President of the Court of Protection, Singh LJ and Baker LJ with judgment handed down on 11 June 2020.

The Court of Appeal recast the decision as being a decision to ‘engage in’ sexual relations rather than a decision to ‘consent to’ sexual relations. Baker LJ held (at para 94) that:

When the ‘decision’ is expressed in those terms, it becomes clear that the ‘information relevant to the decision’ inevitably includes the fact that any person with whom P engages in sexual activity must be able to consent to such activity and does in fact consent to it. Sexual relations between human beings are mutually consensual. It is one of the many features that makes us unique. A person who does not understand that sexual relations must only take place when, and only for as long as, the other person is consenting is unable to understand a fundamental part of the information relevant to the decision whether or not to engage in such relations.”

JB appealed to the Supreme Court.

Supreme Court

In considering the evidence before the Court of Appeal the Supreme Court noted the unchallenged evidence of Dr Thrift who undertook a psychological assessment of JB and concluded that: ‘JB’s marked deficits in social understanding and communication relating to his ASDS and his associated rigidity of thinking are lifelong conditions which are unlikely to change’ and that ‘JB had no insight into the need to change his behaviours’.

In answer to questions posed by Dr Thrift about a person being able to withdraw consent JB replied:

That’s a tricky one … If the person gives consent then she’s already given consent and you have to go through with it to the end. Once you’re half way through she can’t say ‘I don’t give you consent’ ‘cos you’re already doing what you need to do. She cannot change her mind if you are already doing it. Cos it’s her fault in the first place for saying yes. She can’t say yes and then say no. Already said yes and you’ve got your chance.

And that:

if a woman gets drunk at a party and has sex with a man there, is she fair game for anyone else? I’d say she was fair game yes. Especially if she’s done it with one person. Yes if she drinks enough she’s bound to do it with the second one too.

As to the legal question of is the other person’s ability to give and maintain consent throughout ‘information relevant to the decision to “engage in” or “consent to” sexual relations under S3(1)(a) MCA Lord Stephens, giving the leading judgment, held that:

I consider, and the Court of Appeal in this case held at para 48, that the court must identify the information relevant to the decision “within the specific factual context of the case”: see also York City Council v C at para 39. In this way if the matter for decision relates to sexual relations, but does not relate to a particular partner, time or place, so that it is non-specific, as in this case, because JB wishes to “engage in” or “consent to” sexual relations with any woman, then the non-specificity of the matter will inform the information which is relevant to the decision.


Where the matter relates to sexual relations, it will ordinarily be formulated in a non-specific way because, in accordance with ordinary human experience, it will involve a forward-looking evaluation directed to the nature of the activity rather than to the identity of the sexual partner. Moreover, “[to] require the issue of capacity to be considered in respect of every person with whom P contemplated sexual relations would not only be impracticable but would also constitute a great intrusion into P’s private life” (emphasis added)

In relation to the specific circumstances of JB’s case, Lord Stephens held:

The information relevant to the decision includes information about the “reasonably foreseeable consequences” of a decision, or of failing to make a decision: section 3(4). These consequences are not limited to the “reasonably foreseeable consequences” for P (JB), but can extend to consequences for others. This again illustrates that the information relevant to the decision must be identified within the factual context of each case. In this case there are reasonably foreseeable consequences for JB of a decision to engage in sexual relations, such as imprisonment for sexual assault or rape if the other person does not consent. There are also reasonably foreseeable harmful consequences to persons whom JB might sexually assault or rape.

Supreme Court Grounds of Appeal

The first ground of appeal was that the Court of Appeal was wrong to recast “the matter” as JB “engaging in” rather than “consenting to” sexual relations. The Supreme Court held, however, that the wording of section 2(1) MCA is open and flexible, so as to accommodate any matter in relation to which an issue arises as to whether P is unable to make a decision for himself.

Secondly it was argued that JB’s wish to initiate sexual relations was a desire rather than a decision within section 2(1) MCA. The Supreme Court disagreed and held that a desire gives rise to a decision as to whether to fulfil that desire.

The Supreme Court agreed with the Court of Appeal that formulating ‘the matter’ as ‘engaging in’, rather than ‘consenting to’, sexual relations better captured the nature of the issues in this case where JB wanted to initiate relations with others rather than consent to relations proposed by someone else.

It was also argued, on behalf of JB, that extending the information in order to protect the other person or members of the public was inappropriate and that ‘the matter’ should essentially be limited to whether JB could engage in sexual relations. The Supreme Court disagreed and held that information relevant to the decision includes information about the ‘reasonably foreseeable consequences’ of a decision, or of failing to make a decision. Such consequences were not limited to the consequences for JB.

The Supreme Court endorsed the Court of Appeal’s approach where it took the view that ‘amongst the matters which every person engaging in sexual relations must think about is whether the other person is consenting’.

Part of the Supreme Court’s decision also concentrated on whether the test under the MCA created an ‘impermissible’ difference between civil and criminal law. The Supreme Court found that it did not.


This case confirms that a person does have to understand that the other person needs to have the ability to consent to sexual relations in order to have mental capacity to decide to engage in (rather than consent to) sexual relations. On the facts of this case, it was clear to the court that if JB were to engage in sexual relations there was a risk of serious consequences to his mental health and also consequences to the other person if the encounter ended in sexual assault. The court confirmed that there was no separate test for persons with disabilities on the basis that the fact consent must be given before engaging in sexual relations should apply to everyone in society. The particular effects of JB’s autism and other cognitive difficulties impaired his mind to such an extent that he could not understand the information and could not use the information to weigh it as part of the decision-making process.

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