Mental capacity in the Republic of Ireland

Explaining the law surrounding assessing mental capacity in the Republic of Ireland.

  • In its simplest terms, mental capacity is the ability to make our own decisions.
  • All adults are presumed to have the capacity to make decisions about their own medical care.
  • Case law has determined that this presumption should specifically include the capacity to refuse treatment, even if that refusal might result in the death of the patient.1

A patient will not simply 'have' or 'lack' capacity; it is time-specific and decision-specific. A patient's capacity might fluctuate, so they have capacity to makes decisions about their treatment one day and not the next.

Similarly, a patient may have the capacity to make simple decisions about their care but lack the capacity to consent to more complex medical treatment.

The law

  • The above is what is in the 2015 Act, but this Act has not commenced yet. However, the view is that these tests should be followed now, despite the Act not yet being in force. Under the new Act, it will be a functional test.

The law relating to mental capacity has changed over the last few years and now focuses on maximising a patient's potential capacity. The Assisted Decision-Making (Capacity) Act 2015 provides a new statutory framework for assisting patients who lack capacity to have as great an input as possible in their care and treatment.

The Act is not yet fully commenced, but it makes provisions for assisted decision-making in cases where a patient lacks capacity; in particular the Decision Support Service, which is expected to commence operations in 2022. This agency will eventually provide codes of practice to assist doctors in understanding their obligations under the Act.

The Act formalises in law a four stage test for the determination of mental capacity. It states that a patient will lack the capacity to make a decision if they are unable to:

  • understand all of the information relevant to the decision
  • retain the information for long enough to consider it
  • use or weigh up that information in their decision-making process
  • communicate their decision (by any means, including assistive technology, etc.)

Patients who have capacity can make decisions that appear unwise or even bizarre to a treating doctor, but the law is clear that a decision by a competent patient may be irrational in appearance but must still be respected.2

The Act goes on to say that a patient should not be held to lack capacity simply because:

  • they need the information to be communicated to them in a particular way
  • they can only retain the information for a short time
  • they previously lacked the capacity to make the same decision
  • they lack the capacity to make other decisions.

In general terms, if a patient lacks capacity then the Act says a doctor must always treat that patient in accordance with their 'will and preferences'. This is a slight difference in emphasis to previous case law, which required doctors to act in the patient's best interests - although in practice these are likely to be closely aligned, and the current Medical Council guidance still uses this term.

The Medical Council states in paragraph 10.2 of its guidance that doctors should still seek and listen to the views of patients who lack capacity. Doctors should also take reasonable steps to find out whether anybody else has the legal right to make decisions on the patient's behalf, and seek their consent for treatment.

When determining the best interests of a patient who lacks capacity, the Medical Council requires doctors to consider:

  • which treatment would give the best benefit to the patient
  • the previously expressed wishes of the patient
  • the views of other people close to the patient
  • the views of other involved healthcare professionals
  • whether the patient is likely to regain their capacity to make the decision in the future.

Where there is disagreement about a patient's best interests, it may be necessary to apply to a court to determine what these are.



1 Fitzpatrick and anor v FK and anor [2008] IEHC 104, [2009] 2 IR 7

2 In Re a Ward of Court (Withholding Medical Treatment) (No 2) [1996] 2 IR 79

This page was correct at publication on 08/03/2021. Any guidance is intended as general guidance for members only. If you are a member and need specific advice relating to your own circumstances, please contact one of our advisers.

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