Are you OK with cookies?

We use small files called ‘cookies’ on Some are essential to make the site work, some help us to understand how we can improve your experience, and some are set by third parties. You can choose to turn off the non-essential cookies. Which cookies are you happy for us to use?

Skip to content

Mental incapacity and consent to sexual activity: a case study

Sexual offences against a person with a mental disorder: at what point will a “mental disorder” mean a person lacks capacity to consent to sexual activity? Where do we draw the line? And how will incapacity be proved?

Consent to sexual activity, as we know, requires (amongst other things), capacity. There are a number of ways a person might lack capacity: extreme drunkenness, sleep or unconsciousness, to name a few – each of which deserves (and indeed will receive) an essay of its own. But what is the situation when one party’s capacity is impaired by disability, brain damage or disease? How do the criminal courts decide when capacity is sufficiently impaired to negate consent? After all, mental capacity isn’t a binary. People with impairments will have them to differing degrees. How much capacity is enough, and how much is too little? What’s the test?

To consider this question, we will look at the (fictional) case of R v Andrews.

Case study R v Andrews

Mr Andrews is the handyman for a retirement home. One of the residents in the home is Mrs Barrett, who is 96 at the time of this incident, and is in the early stages of Alzheimer’s disease. She lives semi-independently in her own flat but has carers go in twice a day. She has a daughter who manages her money and other affairs. A carer alleges that she saw Mr Andrews kissing Mrs Barrett and fondling her leg.

The evidence is as follows:

Charlotte (carer)

  • Mr Andrews and Mrs Barrett would often have tea and chat.
  • One day I saw his hand up her skirt and he was kissing her on the mouth. She was smiling.
  • I told him to leave. She didn’t want him to go. She said “he’s my boyfriend.”
  • She’s 96. I help her wash, dress and eat. She can’t consent.

Dorcas (daughter)

  • She’s got Alzheimers.
  • She doesn’t know what day it is.
  • She needs help cooking, washing and dressing.
  • I handle her money.
  • She can’t possibly consent


  • She was diagnosed with Alzheimers 2 years ago.
  • It’s a progressive condition.
  • At the time of the incident she was living semi-independently with support.
  • In the months since the incident she has deteriorated significantly and now needs intensive support.

Mrs Barrett has made no complaint, and the Crown have not taken any statement from her. Their position is that she is not competent to give evidence – and given the recent deterioration in her mental state, the defence concede this.

The charge

What is the appropriate charge? There are in fact 2 options for the Crown here, equally appropriate on the facts.

There is no suggestion on the evidence that Mrs Barrett actively objected to Mr Andrews’ touching of her; indeed, the evidence as to that points the other way (smiling, saying “he’s my boyfriend.”). If there is, as the Crown assert, absence of consent, then it is because Mrs Barrett lacks the capacity to consent, due to Alzheimer’s disease; whatever her expressed attitude, without capacity there is no consent. The Crown could therefore charge Mr Andrews with a straightforward sexual assault under s3 of the Sexual Offences Act 2003:

(a) he intentionally touches another person (B),

(1) A person (A) commits an offence if—

(b) the touching is sexual,

(c) B does not consent to the touching, and

(d) A does not reasonably believe that B consents.

Alternatively (and actually, in the real-life case upon which our case-study is based), he could be charged with the rather lesser-known offence contrary to s30 of the Sexual Offences Act: sexual activity with a person with a mental disorder impeding choice:

30 (1) A person (A) commits an offence if—

(a) he intentionally touches another person (B),

(b) the touching is sexual,

(c) B is unable to refuse because of or for a reason related to a mental disorder, and

(d) A knows or could reasonably be expected to know that B has a mental disorder and that because of it or for a reason related to it B is likely to be unable to refuse.

(2) B is unable to refuse if—

(a) he lacks the capacity to choose whether to agree to the touching (whether because he lacks sufficient understanding of the nature or reasonably foreseeable consequences of what is being done, or for any other reason), or

(b) he is unable to communicate such a choice to A.

As we can see from this, the s30 offence will also cover situations other than the one in Andrews: most notably it will also apply when B does have the capacity to choose, but is unable — by virtue of a mental disorder — to communicate that choice (a situation considered in the House of Lords case of Cooper in 2009 [House of Lords in Regina v Cooper [2009] UKHL 42, [2009] 1 WLR 1786]). Section 3 would be unlikely to apply in such a situation. On our facts, however, the 2 potential charges fit the facts more or less interchangeably.

Is one charge better than the other, either for the Crown or the defence? The answer to that seems to be no, not really – in fact, despite the differing wording, the elements the Crown has to prove for each charge are strikingly similar, namely:

  1. That the touching took place, that it was intentional, and that it was sexual;
  2. Absence of consent;
  3. Mr Andrews’ state of knowledge about the absence of consent.

For a s3 sexual assault, the Crown will look to the s74 definition of consent:“A person consents if he agrees by choice, and has capacity and freedom to make that choice”. For the s30 offence, they must prove that Mrs Barrett’s mental disorder is such as to render her “unable to choose” — defined in as lacking “the capacity to choose whether to agree.” The wording, therefore, may differ; but the substance of the issues are identical: was Mrs Barrett’s mental state such that she had capacity to consent?

It is worth noting that, had the facts been slightly different, there might have been very compelling reasons to charge Mr Andrews with one of the specific offences against a person with a mental disorder, rather than with a sexual assault. To see why, we need to look at the relatively infrequently-travelled part of the Sexual Offences Act that creates these offences.

Sexual offences against a person with a mental disorder

Sections 30-41 all deal with sexual offences against people with a mental disorder. All require that the person accused knew, or could reasonably have been expected to know, of the existence of the mental disorder. They are in 3 tranches, of 4 offences each:

  • ss30-33: sexual activity with/causing or inciting to engage in sexual activity/engaging in the presence of/causing to watch sexual activity, with a person with a mental disorder impeding choice;
  • Ss34-38: sexual activity with/causing or inciting to engage in sexual activity/engaging in the presence of/causing to watch sexual activity, by inducement, threat or deception, a person with a mental disorder;
  • Ss39-41: sexual activity with/causing or inciting to engage in sexual activity/engaging in the presence of/causing to watch sexual activity a person with a mental disorder by a care worker.

Only the ss30-33 require that the mental disorder be such as to impede choice; for the others, the existence of the mental disorder alone is sufficient.

If Mr Andrews were a care worker rather than a handyman, therefore, he could have been charged under s39; or, if he had offered Mrs Barrett an inducement to accept his advances, under s34. In either event, the Crown would have had to bring evidence that Mrs Barrett had Alzheimer’s (and that Mr Andrews was aware of it); but they would not have had to deal with the capacity question. Under s30, however, they do.

Have they done so, on the evidence we have seen? In our case study, defence counsel thinks not:

R v Andrews continued

At half time, defence counsel argues that the Crown have not addressed the specific question of whether Mrs Barrett had capacity to choose whether to consent to the limited sexual activity alleged; and the court should therefore dismiss the case on the basis that the jury, properly directed, could not possibly be sure that she was unable to consent.

Prosecuting counsel says “of course we’ve proved it. She’s 96 and she’s got Alzheimer’s, it’s perfectly clear that she lacks capacity. She needs help with dressing and cooking – for heaven’s sake, she doesn’t know what day it is, what’s that if not incapacity? What else could the jury possibly need?

What else indeed?

The answer, in fact, will depend to an extent on the year in which Andrews is being tried. If Mr Andrews was being prosecuted shortly after the coming into force of the 2003 Act, there would be very little by way of definitions or authorities to guide the court. We do get a definition of “mental disorder,” which s79(6) of the Sexual Offences Act tells us “has the meaning given by section 1 of the Mental Health Act 1983,” namely “any disorder or disability of the mind.” Alzheimer’s, unsurprisingly, falls squarely within the definition (and as we have seen, if Mr Andrews was being prosecuted under ss33-41 of the Sexual Offences Act, that would be sufficient). What we do not get from the Act is any guidance at all as to how lack of capacity consequent upon that mental disorder is to be interpreted, or evidenced.

If, then, Mr Andrews were being tried in, say, 2004, the Crown’s approach might be perfectly sufficient according to the law at the time. After all, if the Crown’s case, even now, were that a complainant lacked capacity because she was unconscious through drugs or alcohol, it would be unobjectionable for them to adduce a patchwork of pieces of evidence to that effect, and invite the jury to conclude incapacity. Criminal cases are very often decided on an accumulation of pieces of evidence, none of which are sufficient in themselves to prove the Crown’s case, but when taken together, form an overwhelming picture. In the immediate wake of the 2003 Act there would have been no particular reason to think that the approach towards proving mental incapacity was any different.


After the 2003 act, however, there followed a decade during which there were rumblings of change in the law relating to capacity. Following several commissions and reports into decision-making for the incapacitous, the Court of Protection, which had formerly dealt only with finances, had its powers extended to social and welfare matters. This was by means of the Mental Capacity Act 2005 (which did not actually come into force until 2007). It created that which is lacking in the Sexual Offences Act: a test for determining capacity. However, despite subsequent Court of Protection decisions which spoke of the desirability of having the same test in criminal and civil jurisdictions, [Re MAB [2006] EWHC (Fam) 168 and Re MM [2007] EWHC (Fam) 2003; D County Council v LS   [2010] EWHC 1544 (Fam), [2010] COPLR 331] it did not apply to the criminal law.

If R v Andrews were being heard after 2007, then, the court could have looked to the MCA for guidance on how to assess capacity if they had chosen to; but would not have been required to do so. Even in 2009, when the House of Lords considered the case of Cooper, a case concerning the s30 offence, that did not change: it’s a case well worth reading, as it contains some interesting history regarding the law as it relates to people with mental disorders. What it does not do is provide any guidance as to how the Crown in the case of Andrews have to prove Mrs Barrett’s incapacity.

2014: R v A(G)

The watershed came in 2014, with the case of R v A(G). [[2014] EWCA Crim 299, 2014 WL 2557988] The Court of Appeal in this case dealt head-on with just that question. It was a prosecution for a s3 sexual assault, rather than a s30 offence – but as we have seen, the charges in some cases will be interchangeable, and A(G) was one such. The Appellant (M) and Complainant (F) had learning difficulties, and sexual activity took place between them. The Crown’s case was that her learning difficulty was such that she lacked capacity to consent. (So was his – in fact, his disability was the more severe, and he was found unfit to plead because of it. The Court of Appeal had much to say about the decision to charge in the circumstances). The question, therefore, arose then as it does in our case study: how does the Crown prove that a complainant lacks the capacity to consent? What is the test, and what evidence is required?

The answer, said the Court of Appeal, is threefold:

  • The tests in the Mental Capacity Act will apply;
  • They must be proved to the criminal standard;
  • Expert evidence is required.

The Mental Capacity Act 2005

Turning to the Mental Capacity Act, and to the Court of Protection, is a something of an eye-opener for the criminal lawyer. Not only is it law with which we are likely to be unfamiliar; but the entire approach towards the vulnerable person is different, and this difference becomes immediately apparent in s1:

The principles

(1) The following principles apply for the purposes of this Act.

(2) A person must be assumed to have capacity unless it is established that he lacks capacity.

(3) A person is not to be treated as unable to make a decision unless all practicable steps to help him to do so have been taken without success.

(4) A person is not to be treated as unable to make a decision merely because he makes an unwise decision.

(5) An act done, or decision made, under this Act for or on behalf of a person who lacks capacity must be done, or made, in his best interests.

(6) Before the act is done, or the decision is made, regard must be had to whether the purpose for which it is needed can be as effectively achieved in a way that is less restrictive of the person’s rights and freedom of action.

The foundational principles of the act are geared towards promoting the autonomy of the individual. In the criminal courts, we are well used to vulnerable people: we have special protections for them as witnesses, and enhanced sentences for those who offend against them. The system aims to protect them, and views with extreme disfavour potential exploiters of their vulnerability. What is rarely considered in the criminal courts is their autonomy, and the effect of protectiveness on that autonomy; yet that is the question which is central to the decisions of the Court of Protection. Usefully for our purposes, the Court of Protection deals frequently with the capacity to consent to sexual activity – and often in cases of Alzheimer’s. Its approach, in line with the principles in s1 of the MCA, is to assume capacity until proved otherwise, and to preserve autonomy – “a person’s rights and freedom of action” s1(6) — where possible:

“The intention of the [Mental Capacity] Act is not to dress an incapacitous person in forensic cotton wool but to allow them as far as possible to make the same mistakes that all other human beings are at liberty to make and not infrequently do” [A NHS Trust v P [2013] EWHC 50 (COP)]

The point is made repeatedly that sexual decision making is not, even in people of full capacity, generally a very sophisticated business; it is “largely visceral, not cerebral.[IM v LM, AB, Liverpool City Council [2014] EWCA Civ 37, 2014 WL 16530] Mrs Barrett’s decision-making in this regard, therefore, shouldn’t be held to a higher standard than that of anybody else. The Court of Protection is also very alive to the ramifications for the individual of finding that they lack capacity to consent:

“It is important to identify that depriving an individual of a sexual life in circumstances where they may be able to consent to it….. is depriving them of a fundamental human right” [LB Tower Hamlets v NB & AU [2019] EWCOP 27]

It is not a decision to be made lightly; nor is it right to “err on the side of safety” – because that has consequences for the liberty of the individual.

This is an approach which perhaps doesn’t feel natural to the Crown Court in Andrews, which is used to its priorities being the protection of the vulnerable, rather than the preservation of their autonomy; but it is an approach that, post R v A(G), they are obliged to take.

What is the test?

It is s2(1), expanded upon by s3, which creates the statutory test:

2 People who lack capacity

  • For the purposes of this Act, a person lacks capacity in relation to a matter if at the material time he is unable to make a decision for himself in relation to the matter because of an impairment of, or a disturbance in the functioning of, the mind or brain.
  • It does not matter whether the impairment or disturbance is permanent or temporary.

(3) A lack of capacity cannot be established merely by reference to—

(a) a person’s age or appearance, or

(b) a condition of his, or an aspect of his behaviour, which might lead others to make unjustified assumptions about his capacity.

R v Andrews

Let’s apply this to R v Andrews. The Crown have proved, with medical evidence, the existence of a disorder of the mind, namely Alzheimer’s. But what evidence do they suggest they have that proves Mrs Barrett was unable to consent? Prosecution counsel seems to rely on the following:

  1. She has Alzheimer’s
  2. She doesn’t know what day it is
  3. She needs help with money, food and dressing
  4. She’s 96.

If we apply the criteria in the Mental Capacity Act to each of the 4, we can immediately see that prosecution counsel may be in difficulties. Number 1 – the fact that she has Alzheimer’s —  falls foul of s2(3)(b): incapacity cannot be proved merely by reference to a condition. Neither can it be proved by factor number 4, her age, by virtue of s2(3)(a).

Numbers 2 and 3, meanwhile, fall foul of s2 (1): a person lacks capacity in relation to a matter if at the material time he is unable to make a decision for himself in relation to the matter. In other words, capacity is decision-specific: a person may be unable to make decisions about one matter, but able to about another. The question here is not whether Mrs Barrett is oriented in time, or can make decisions about money, food and clothes. The question is whether she can make a decision whether to receive Mr Andrews’ advances. What’s more, the court should keep in mind that it doesn’t matter whether or not it’s a bad decision: s1(4) A person is not to be treated as unable to make a decision merely because he makes an unwise decision.

Section 3 expands on the test in s2:

  • Inability to make decisions

(1) For the purposes of section 2, a person is unable to make a decision for himself if he is unable—

(a) to understand the information relevant to the decision,

(b) to retain that information,

(c) to use or weigh that information as part of the process of making the decision, or

(d) to communicate his decision (whether by talking, using sign language or any other means).

(2) A person is not to be regarded as unable to understand the information relevant to a decision if he is able to understand an explanation of it given to him in a way that is appropriate to his circumstances (using simple language, visual aids or any other means).

(3) The fact that a person is able to retain the information relevant to a decision for a short period only does not prevent him from being regarded as able to make the decision.

(4) The information relevant to a decision includes information about the reasonably foreseeable consequences of—

 (a) deciding one way or another, or

 (b) failing to make the decision.

How is the test applied?

Ultimately, it will be for the jury to decide, having been directed about the test. [Although note that “That is not to say that a jury will need to be directed in strict accordance with the language used by and steps to be adopted in accordance with proceedings brought pursuant to the Mental Capacity Act 2005] However, they should be assisted by expert evidence.

When capacity is an issue in the Court of Protection, as it so often is, then (as a brief trawl of the authorities reveals) this is invariably seen as an area for expert opinion. Indeed, it appears that there is a flourishing industry of “capacity specialists,” whose existence is rarely guessed at in the criminal courts. There is no statutory requirement for an expert (as there is, for instance, in the assessment of fitness to plead in criminal proceedings), and the court in Andrews pre- R v A(G) might have been forgiven for seeing no need for one. We do not, after all, routinely hear expert opinion when the issue is incapacity through drink or drugs.

In A(G), however, the Court of Appeal said this:

“It appears to us that it will inevitably be the case that, if capacity is an issue, an expert will be called to provide evidence which will not otherwise be within the common experience of the jury.” [R v GA 2014 WL 2557988 (2014)]

This may fall short of imposing an absolute requirement; but it is hard to imagine a clearer indication that expert evidence is desirable. There is none in R v Andrews. There is, as we have seen, the medical evidence from the GP simply confirming that she has Alzheimer’s; but (as per s2(3)(b)) this is not sufficient. The opinions of Charlotte and Dorcas (“she can’t consent”) must surely be inadmissible as opinion evidence – but even if they were before the jury, they make no attempt to address the test in the MCA. Charlotte and Dorcas can of course give evidence about Mrs Barrett’s functioning generally, and the sort of help she needs. A jury could in theory use this information to apply the MCA test and reach their own finding as to capacity. But in the light of A(G), this is unlikely to be enough.

We will return to our case study, assuming now that it is being heard post-2014.

R v Andrews: ruling

Following the half-time submission, the judge rises and hurriedly reads R v A(G). Returning to court, she rules as follows:

  • “The Crown have proved Mrs Barrett suffers from Alzheimer’s disease. They have brought evidence that, as a result, she requires help in some areas of life, such as self-care and managing her money; and that she is not always oriented in time. These matters are not in dispute. It is undoubtedly the case that Mrs Barrett has some functional difficulties, and that there are areas of her life where she is not able to manage for herself. If the question before me were “is Mrs Barrett a vulnerable person?” I would have no hesitation in saying that she is.
  • However, that is not the question. The question is this: is there sufficient evidence for a jury, properly directed, to find that at the time of the touching, Mrs Barrett’s mental disorder was such that she was unable to choose whether to consent to it?
  • When deciding whether the Crown have proved that Mrs Barrett was unable to choose whether to consent, the jury must, in effect, apply the test in the Mental Capacity Act, sections 2 and 3. This requires them to begin with a presumption that Mrs Barrett did have capacity, and ask themselves whether the Crown have disproved this, to the criminal standard.
  • They have heard evidence that Mrs Barrett requires help with various daily functions, including managing her money, dressing and cooking; and that – in the words of her daughter – “she doesn’t know what day it is.” The Crown invite the jury to infer that these limitations must necessarily mean she lacked capacity to consent to sexual touching. They rely in addition upon her advanced age, and the diagnosis of Alzheimer’s disease.
  • I remind myself of s2(3) of the Mental Capacity Act: incapacity is not to be assumed because of a person’s age, or because of a condition of theirs. The Act refers to the risk of this leading to unjustified assumptions about capacity. I do not consider, therefore, that Mrs Barrett’s age, or the diagnosis of Alzheimer’s, are in themselves matters capable of persuading a properly directed jury that she was incapable of consenting to the touching.
  • Equally, her difficulties in other areas of are not sufficient in themselves, because the question is not whether Mrs Barrett had capacity in other areas of life, but whether she had the capacity to choose whether to consent to being touched by Mr Andrews in the way alleged. A person may not be oriented in time sufficiently to know what day it is, but may nonetheless be able to understand the nature of sexual touching sufficiently to be able to make a decision as to whether to consent to it.
  • I note the absence of expert evidence in relation to capacity. It would have been open to the Crown to have had Mrs Barrett assessed by a capacity expert shortly after the incident. They did not do so, and I understand that Mrs Barrett’s mental state has unfortunately deteriorated significantly in recent months, so that any assessment now would not shed any light on her capacity at the relevant time. It is a great pity that the Crown did not have such an assessment done; there is no statutory requirement for expert evidence where capacity is in issue, but the Court of Appeal in R v A(G) have given a very strong indication as to its desirability, and I consider the jury would have been greatly assisted by expert evidence in this case.
  • I therefore conclude that, in the absence of any evidence directly relating to capacity to consent to sexual touching, there is insufficient evidence for a jury, properly directed, to be sure that Mrs Barrett lacked that capacity at the time of these events. I therefore stop the case at this point. Mr Andrews, I will direct the jury to return a verdict of “not guilty,” after which you will be free to leave this court.”

This article entitled  “Mental Incapacity and Consent to Sexual Activity: a Case Study ” was written by Kate Roxburgh. For further information on her practice or to instruct Kate, please contact Robin Driscoll, Senior Criminal Clerk on Telephone: 020 3334 4253 or Email: