Whether a person has the mental capacity under the Mental Capacity Act 2008 (MCA) usually is an issue when a lasting power of attorney (LPA) is challenged.


Section 4(1) of the MCA states that a person lacks capacity… if the person is unable to make a decision for himself or herself in relation to the matter because of an impairment of, or disturbance in the functioning of, the mind or brain.

Therefore, to fall under the ambit of s 4(1) of the MCA as a person who lacks capacity, two limbs need to be fulfilled:

Limb 1: the person is unable to make a decision.

Limb 2: there needs to be an impairment, of, or disturbance in the functioning of, the mind or brain (this is a question of how the mental function of the mind or brain has been impaired by a certain disease) in relation to the matter (i.e. it is decision specific).

And the words “because of” in s 4(1) of the MCA required that there be shown a causative nexus between both limbs (Re BKR [2015] 4 SLR 81 (“Re BKR”) at [88] to [120]), although the mental impairment need not be the sole cause of the inability to make decisions.

The court in Re BKR at [134] broke up the test in section 4(1) of the MCA into a functional and clinical component. Limb 1 being the functional component and limb 2 being the clinical component where the court is interested in whether the inability is caused by a mental impairment.


We first deal with Limb 2.

To fulfil limb 2, a medical report from medical professions needs to be adduced. This medical report should state that the person in question was suffering from a certain condition or disease and this condition or disease impaired the person’s mental function.


We next deal with Limb 1.

The court would also have to consider the functional component and decide as to the degree the person’s mental functioning is compromised because of his medical condition. This ultimately is for the court to decide whether the person lacks the ability to make decisions (Limb 1) within the meaning of s 5(1) MCA (Re BKR at [134]).

(Imagine a party wanting to challenge an LPA and that party adduces a medical report that the maker of the LPA was suffering from dementia and that party says “I have evidence that this person is suffering from dementia in this medical report and therefore he does not have the mental capacity to make the LPA”. This statement is incorrect because only the court can come to the decision whether the maker of the LPA has the mental capacity and not the medical doctors who issued the medical report.)

For a person to be unable to make decisions, he must be unable to:

  1. Understand the information relevant to the decision.
  2. Retain that information.
  3. Use or weigh that information in his decision-making process.
  4. Communicate his decision (through talking, sign language or other means.

This should be read conjunctively. This means that for a person to have the ability to make decisions, he should be able to do all four items (a) to d)). This meant that the court’s assessment should be a holistic one and the inability to do a single one would mean that he is unable to make decisions (BUV v BUU and another and another matter [2020] 3 SLR 1041 at [31]).


We next need to determine if there is a causative nexus between Limb 1 and Limb 2

This is an analysis of the facts to show that the medical condition in Limb 2 has a causative nexus that let to the person being unable to make decisions in Limb 1.

(You cannot make an argument that the person has a medical condition, say he has a stroke or has cancer, but cannot show that that medical condition caused him to be unable to make decisions. It has to be something like the person has a medical condition like dementia or schizophrenia and then that medical condition caused him to be unable to make decisions.)


We must also consider undue influence and how it affects a person’s mental capacity to make decisions

Undue influence in the context of mental capacity is contract law undue influence. The test for undue influence is stated in BOM v BOK [2019] 1 SLR 349.

As there is an issue of [proven/ potential] undue influence, this is relevant to the issue of mental capacity in three ways:

  • It becomes material whether P is able to retain, understand or use the information that relates to whether there might be undue influence being applied.
  • The court must consider whether P’s susceptibility to undue influence is caused by mental impairment.
  • P cannot realistically hope to obtain assistance in making decisions.

The issue would usually be whether the LPA that was executed is valid (i.e. whether the person in question had the requisite mental capacity to execute the LPA). Alternatively, the person in question does not have an existing LPA and we are considering whether he has the requisite mental capacity to make a valid LPA. In both cases, if the person is found not to have the requisite mental capacity to execute a valid LPA, the option of the Court appointing a Deputy must be considered.

If the person in question has no LPA and lacked the mental capacity to execute an LPA

If the person in question does not have a valid LPA, the Court can appoint a Deputy to make decisions on his or her behalf regarding his or her personal welfare, property and affairs (s 20 read with s 22 and 23 of the MCA). The Court can subject the Deputy to any restrictions. The Court’s decision should be based on that person’s best interest (s 6 of the MCA).