The concept of capacity is a ‘bedrock term’ when it comes to understanding mental health law.


In the ordinary sense, the capacity of a person can be described as the ability of a person to do something. Capacity in the legal sense has the same meaning, but the concept is simply put into a legal context: Capacity can be described as the ability of a person to do something that has binding legal consequences.


The question of somebody’s mental health is legally significant in the sense that it might affect your capacity to do some legal act.

In the medical sense the terms ―’mentally ill’ or ‘suffering from a mental disease’ or even ‘intellectual disability’ all mean something significant, and might stay with you for the rest of your life (a ‘label’). This label can be hugely debilitating for a person with a disability who is attempting to make their own way in society.

Accordingly, in the legal sense these ‘labels’ rather act as a starting point into an investigation to determine the capacity of the person with a mental illness or intellectual disability.

An illness or disability should have little legal significance unless it prevents you from being able to perform some or other legal act which would include understanding the potential consequences of that act.

Lawyers would argue that a person’s capacity or competency should always be measured in terms of their ability to do a specific thing, which is why we often talk about ‘functional capacity’. For example, we say that a person has the capacity to consent to medical treatment if that person can understand the need for the treatment, the consequences and risks of the treatment, and what would happen if they refused that treatment. Similarly, we would say that a person had the capacity to make a will if they understood what a will was and what it did, and that the property that they knew they owned would go to the people mentioned in the will on that person’s death.

However, this functional approach is not always automatically applied in Irish law. There are still remnants of what can be called a ‘status approach’. The status approach evaluates somebody on the basis of their disability without actually enquiring into the ability of that specific person to make decisions. This is sometimes called ‘absolute capacity’ and bears similarities to ‘labelling theory’.

The Law Reform Commission of Ireland recognised this problem as early as 2006 and in its report Vulnerable Adults and the Law (LRC 83/2006) the Commission recommended that ‘capacity will be understood in terms of an adult’s cognitive ability to understand the nature and consequences of a decision in the context of available choices at the time the decision is made’. This is a clear endorsement of the functional approach.

The ‘functional approach’ considers whether the person is able, at the time when a particular decision has to be made, to understand the nature and effects of that particular decision, focusing on the functioning of the individual with regard to understanding and appreciating the issues involved in that decision. In short, the functional approach to assessing capacity is time-specific and issue-specific.

The fact that a person has the capacity to perform one type of legal act does not automatically mean that they have the capacity to perform all sorts of other legal acts. Their capacity must be measured at the time in relation to that specific act. The converse is also true – the fact that a person is found to be incapacitated to do a certain legal act does not disqualify him or her from doing any other legal acts. Each situation is regarded separately and by that is meant that even identical situations that happen at different times must be regarded separately, just as we would separately assess different situations at the same time.

However, because it would be a cumbersome process assessing somebody’s capacity every time they were called on to make a decision, a person is deemed (which means that the law will take it as a fact until the contrary is proved) to have the capacity to give true consent when that person is an adult (over the age of eighteen years) and possessed of a sound mind.

What the functional approach means is that we must look at the type and complexity of the decision that a person is being asked to make, and then taking in account our knowledge of the person’s intellectual and emotional maturity and competence, decide whether that person has the ability to properly understand what it is they are being asked to decide. In other words, a person’s capacity must be assessed in light of the decision the person is being asked to make. For this reason the phrase ‘relative capacity’ is often used, because the capacity is measured in relation to the task that the person is required to perform, which is pretty much the same as the functional approach.

The law is not necessarily concerned about the symptoms or manifestations of a person’s mental illness or disability, but rather whether the person can understand the nature and consequences of the proposed action, and in the light of that understanding, make a decision whether to proceed with that action or not. The fact that a person suffers from some mental disability does not automatically disqualify that person from making the decision. Where it is clear that the person fully understands what it is that they are being asked to do, and the nature and consequences of their actions if they do the thing asked of them, and also the consequences of refusing to do the thing asked of them, somebody else cannot ignore the wishes of that person simply because they have been previously diagnosed with a mental illness or intellectual disability.

When a person is declared incapacitated, that decision has huge consequences for their future life. The person loses the freedom to make decisions for himself, at the very least in relation to the areas that the incapacity affects. Others will decide for that person. Depending on the nature and extent of the incapacity, he or she might be told where to live, what medical treatment to have, what contracts they may enter, whether she can give away her property or leave it to others in her will, whether he or she can have sex or marry, even whether they can open a bank account.

This is really about human rights like the right to autonomy, the right to self-determination, and the right to dignity. By simply labelling somebody as ‘mentally ill’ or ‘intellectually disabled’ and thereafter ignoring their wishes, we are stripping that person of even the most basic human rights.


Assessing Capacity

A well-known test for assessing the capacity of a person is known as the Re C Test after a famous English judgment of the same name. This test comprises three questions:

Is the patient able to comprehend and retain the necessary information?

In other words, did the mental illness complained of prevent the patient from storing information in order to mull over that information before making a decision. Certain mental illnesses, like Alzheimer’s disease, attack the memory directly, and the nature of the disease and its direct impact on the memory need to be carefully considered.


Is the patient able to believe the information given to him or her?

If the patient cannot take the health professional seriously, or if they think that the health professional is part of a greater conspiracy against them, then clearly the patient will not believe the information being given by that health professional. So, the fact that a person is diagnosed as a paranoid schizophrenic is clearly important when considering this second requirement. Again, the prudent health professional will not merely rely on the diagnosis, but will rather question the patient on why the medical advice is being refused. If the patient replies that the doctor is ‘one of them’ or words to that effect, the health professional has grounds to believe that the patient fails on this second leg of the capacity test.


Is the patient able to consider and weigh the information, including balancing the risks against the advantages and needs, and finally arrive at a decision?

The final test involves an assessment of the patient’s cognitive abilities to understand and assess the medical advice, including both ‘pros and cons’, and thereafter make a considered decision. In other words, the ‘brain power’ and relative intelligence of the patient will need to be assessed in relation to the nature and complexity of the medical advice presented. So a person with an intellectual disability might succeed on the first two legs of the test, but not be able to assess or analyse the information sufficiently to make an informed decision, and so could fail on the last leg.


Although this test talks of a patient and the case itself dealt with the refusal of medical treatment, it has become a test of universal application in any situation where a care professional requires consent from a service user. To touch somebody without their consent is an assault. However, that service user can only consent or refuse to be touched if they have the capacity to do so. Hence the need for a practical and understandable test for assessing capacity “on the spot”.

Many argue that the Re C test is limited by the second question which was based on the facts of the case – the patient was paranoid. This limitation has been recognised by the Assisted Decision-Making (Capacity) Act 2015. In Section 2, the Act says that a person lacks the capacity to make a decision if they are unable:

  • To understand the information relevant to the decision
  • To retain that information long enough to make a voluntary choice
  • To use or weigh that information as part of the process of making the decision, or
  • To communicate their decision.


This amends the traditional Re C test by dropping the second question (does the person believe you?) and adds another requirement: can the person communicate their decision?  The word communicate must be given a wide meaning, and clearly is not limited to speech, writing or sign language, but could include electronic and other means of communication.


The International Disability Alliance (IDA) has challenged the functional test for legal capacity on the basis that its application constitutes discrimination in exercising the right to legal capacity on an equal basis with others. Instead, the IDA argues that disability should be recognized as “functional diversity” and that in the exercise of legal capacity the focus must be on providing supports and accommodations. The Alliance argues that the right to make decisions according to one’s “will and preferences” can never be restricted on the basis of functional diversity or disability. In other words, instead of focusing on whether somebody has capacity or not, we should be looking at ways to assist people so that everybody can make their own decisions. This is in line with the social model of disability discussed in the previous blog. This theme will be further explored in a future blog when we discuss the abovementioned 2015 Act.


Categories Mental Health Law

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