Mental capacity in Singapore is assessed under the Mental Capacity Act 2008, and the assessment is narrower than most people expect. It is not a global judgment about whether someone is “of sound mind”. It asks whether this person, at this moment, can make this particular decision, and it starts from the presumption that they can.
That framing matters because capacity determines whether a Lasting Power of Attorney can be made, whether a will stands, whether a deputy must be appointed, and whether an adult can be prevented from doing something they want to do, the instruments covered in the wills, probate and incapacity planning guide. Getting the question wrong in either direction causes real harm: assuming incapacity strips someone of decisions they were entitled to make, while assuming capacity leaves a vulnerable person exposed.
The five statutory principles
The Act sets out principles that govern every capacity question. They are not background commentary; they are the operative starting point, and an assessment that ignores them is defective.
- A person is presumed to have capacity unless it is established that they lack it. The burden falls on whoever asserts incapacity, and it is not discharged by a diagnosis, an age, or a general impression.
- A person is not to be treated as unable to make a decision unless all practicable steps to help them have been taken without success. Explaining things simply, using an interpreter, choosing a time of day when the person is at their best, involving someone they trust, breaking a decision into parts, using pictures or written prompts: all of that must be tried first.
- An unwise decision does not by itself indicate incapacity. A person may refuse treatment, give money away, or choose to live somewhere unsafe, and still have capacity. The law protects the process of deciding, not the wisdom of the outcome.
- Anything done for a person who lacks capacity must be in their best interests. That is a structured assessment, not a substitution of the decision-maker’s own preferences.
- It must be the least restrictive option. Before acting, consider whether the purpose can be achieved in a way that interferes less with the person’s rights and freedom of action.
Read together, these principles push consistently in one direction: towards supporting the person to decide for themselves wherever that is possible.
The two-part test
Where the presumption is displaced, the Act applies a test with two limbs, and both must be satisfied.
The diagnostic element
There must be an impairment of, or a disturbance in the functioning of, the mind or brain. It can be permanent or temporary. Dementia, stroke, brain injury, learning disability, mental illness, delirium, and the effects of intoxication or medication can all qualify.
On its own it establishes nothing. A dementia diagnosis is not a finding of incapacity, and people in the earlier stages of dementia routinely retain capacity for most or all decisions.
The functional element
Because of that impairment, the person must be unable to do at least one of the following in relation to the decision in question:
- Understand the information relevant to the decision, including the reasonably foreseeable consequences of deciding one way or another, or of not deciding at all, presented in a way appropriate to the person.
- Retain the information long enough to make the decision. Retaining it only briefly does not mean incapacity, provided it is long enough for the decision itself.
- Use or weigh the information in the process of deciding. This is where many genuine cases turn. Someone may repeat the facts accurately but be unable to apply them. A person who acknowledges they cannot walk unaided yet cannot weigh that against a plan to live alone is failing this limb, not the understanding limb.
- Communicate the decision, by any means: speech, writing, gesture, blinking, an assistive device. Only where no method of communication succeeds does this limb bite.
The causal link is essential. The inability must be because of the impairment. Someone who refuses to engage out of anger, or who cannot follow an explanation given only in a language they do not speak, does not thereby lack capacity.
Decision-specific and time-specific
Two features of the test are consistently misunderstood, and both follow directly from how it is framed.
Capacity is decision-specific. It is assessed against a particular decision, not in the abstract. The information relevant to choosing what to wear is trivial; the information relevant to selling a flat and restructuring one’s finances is not. The same person can plainly have capacity for the first and plainly lack it for the second, on the same afternoon. There is no such thing as a general certificate that someone “has capacity”.
Capacity is time-specific. It is assessed at the moment the decision is made. Many conditions fluctuate: delirium during an infection, the effects of medication, the daily pattern of dementia, mental illness that remits and relapses. A person who lacks capacity on Tuesday may have it on Thursday, and a decision made in a lucid interval can be perfectly valid. So assessments should be timed rather than merely conducted: if someone is reliably better at a particular time of day, that is when the assessment should happen and when the decision should be taken.
Who assesses capacity, and when a medical report is needed
| Situation | Who assesses | Formal report needed? |
|---|---|---|
| Everyday decisions: meals, clothing, routine care | The carer, family member or professional supporting the person at the time | No |
| Medical treatment | The treating doctor, for the specific treatment proposed | Recorded in the clinical notes rather than a separate report |
| Making an LPA | The certificate issuer, who must be satisfied the donor understands and is not under pressure | Sometimes; a medical opinion is often obtained where age or health raises a question |
| Deputyship application | A registered medical practitioner, in the prescribed form for the court | Yes |
| Making a will | The lawyer taking instructions, applying the testamentary capacity test | Advisable where the testator is elderly or unwell |
| Disputed cases | The court, on medical and other evidence | Yes, usually including specialist evidence |
For an LPA, the certificate issuer, whether an accredited medical practitioner, a practising lawyer or a registered psychiatrist, must certify that the donor understands the purpose and effect of the LPA and is not acting under undue pressure. Where there is any doubt, a contemporaneous medical opinion protects the Lasting Power of Attorney against later challenge.
For a deputyship application, the court requires a medical report in the prescribed form addressing the statutory test and the specific decisions the deputy would make. A general letter saying a person “has dementia and cannot cope” will not do; the report must engage with the two limbs and with the particular decisions in issue.
Where a person has made an advance medical directive, capacity is relevant at both ends: the person must have had capacity when they made it, and the directive only comes into operation once they no longer have capacity to decide about the treatment in question.
Testamentary capacity is a different test
Capacity to make a will is not governed by the Mental Capacity Act test. It is a distinct common-law standard, long established, and it sits alongside the statutory framework rather than being replaced by it.
In broad terms, a person making a will must understand the nature of the act and its effects; understand the extent of the property they are disposing of; be able to comprehend and appreciate the claims of those who might expect to benefit; and be free of any disorder of the mind that perverts their sense of right or prevents the exercise of their natural faculties in disposing of their property.
The third element does real work. A testator does not have to provide for the people with claims on their estate, but they must be capable of bringing those people to mind and considering them. A testator who has forgotten a child exists is in a different position from one who has considered that child and chosen to exclude them.
Where a will is made by someone elderly or unwell, prudent practice is to have capacity assessed and recorded at the time, ideally by a doctor who examines the testator and reads the draft will. That contemporaneous record is worth far more than expert opinion reconstructed years later from medical notes. Challenges on this ground are among the most common in estate litigation, and the routes are set out in the guide to contesting a will in Singapore. The related practical steps are covered in the guide to writing a will.
When the family disagrees
Capacity disputes within families usually have a shape: one relative believes a parent can no longer manage and should hand over control; another believes the parent is fine and is being pushed; and both are partly right, because capacity varies by decision and over time.
A few things help. Get a proper assessment from a doctor who knows the person, and be precise about which decision is in question: “can she manage her own bank account” is answerable in a way that “does she still have capacity” is not. Where capacity fluctuates, ask for assessment on more than one occasion. And separate the capacity question from the disagreement about what should happen: a person with capacity is entitled to make the choice you disagree with.
Watch also for the reverse problem. Sometimes an assertion of incapacity is a means of taking control, and sometimes an assertion of capacity comes from the person who benefits from decisions the adult is being pressured into. Where there are signs of pressure or financial harm, the routes for raising them are set out in the guide to what to do when a donee or deputy abuses their position, and where an adult is at risk and unable to protect themselves, the Vulnerable Adults Act provides protective powers.
If the disagreement cannot be resolved, the court can make a declaration as to whether a person has capacity in relation to a particular matter, and can decide the underlying question at the same time. That is the definitive answer, but it is also the slowest and most expensive one, which is the strongest possible argument for making an LPA while capacity is not in doubt, so that the question never has to be litigated at all. If you want advice on your own situation, we can connect you with a licensed Singapore law practice.
