The Mental Capacity Act: a practical guide for students

IMCA, OPG, LPA – these are all commonly used terms you may come across while on placement. But what do they mean? Dr Ellie Mein decodes the Mental Capacity Act.

Learning medicine involves becoming familiar with entirely new language. Between Latin names, technical jargon, acronyms and abbreviations it can be easy to feel overwhelmed. And this is before you take into account terms derived from legislation relevant to the practice of medicine.

Mental capacity is the ability to make a decision that impacts on a person's life. It means that a person is able to make a decision about their own care and treatment. As such, assessing mental capacity is an integral part of being a doctor.

The Mental Capacity Act 2005 (MCA) and its accompanying Code of Practice provides a legal framework for decisions about those aged 16 or over in England and Wales who may lack the ability to make decisions for themselves.

Below are some common terms that you may hear on your clinical placements that relate to the care of patients who lack capacity. Providing medical care for these patients presents some challenges, so having a grasp of some of the most common terms from the MCA can help you to understand specific challenges and requirements that can arise while caring for these patients.

Mental capacity

Mental capacity is the ability to make a particular decision at a particular time.

Two-stage assessment of capacity

Establishing if someone has capacity to make a particular decision involves a two-stage test.

Stage one: Is there is an impairment of or disturbance in the functioning of the patient's mind or brain, whether temporary or permanent? If the answer is yes, then you move to the next stage (stage two).

Stage two: Is the impairment or disturbance sufficient that, even with all practical and appropriate support, the patient is unable to make a particular decision at the time it needs to be made?

Lack of capacity

If a person has a disturbance of the mind or brain (stage one of the two-stage test), that person lacks capacity to make a particular decision if they cannot understand information relevant to the decision, retain it in their mind, weigh it as part of the decision-making process, and/or communicate their decision. Mental capacity is time and decision specific. Someone might lack capacity to make a big decision but retain capacity to make smaller decisions, and capacity can fluctuate.

Presumption of capacity

Every person aged 16 or over must be assumed to have mental capacity to make their own decisions, unless proved otherwise. Don't assume someone lacks capacity based on their medical condition or disability, or because they make what you view as an unwise decision.

Best interests

If a patient requires medical treatment but lacks the capacity to consent to it, the treating doctors may need to make a decision based on their best interests.

The idea of best interests and how to assess this can be confusing, and it's important to note that 'best interests' is not defined by the MCA or the Code of Practice. Chapter 5 of the MCA Code of Practice provides a checklist of factors to consider when working out best interests.


A person can, while they still have capacity, appoint one or more attorneys to make decisions (within a defined scope) for them. This is called a lasting power of attorney (LPA). An LPA for health and welfare only comes into effect when the person loses mental capacity to make their own decisions.

A person can also appoint an LPA for their financial affairs.

You may also come across the term enduring power of attorney (EPA), which is similar and was made under previous legislation. But an EPA only applies to financial affairs, not to health decisions.


In relation to the MCA, a donor is an individual who has made an LPA or EPA. So, for cases involving doctors, it will usually be the patient.

Court of Protection

The Court of Protection is the specialist court that is responsible for decisions or actions taken under the Mental Capacity Act. You can find out more about what action it can take here, including making decisions or orders on financial or welfare matters affecting people who lack capacity. For example, disputes about administering COVID-19 vaccinations to patients lacking capacity were escalated to the Court of Protection for a decision.

This court can also decide whether an LPA or EPA is valid, and remove deputies or attorneys who fail to carry out their duties.


A court-appointed deputy is someone appointed by the Court of Protection with ongoing legal authority to make decisions for someone who lacks capacity. There are two types of deputy: a property and financial affairs deputy who deals with financial matters, and a personal welfare deputy who makes decisions about medical treatment and care.

If a person did not appoint an LPA while they had capacity to do so, the Court of Protection might appoint a deputy after the person has lost capacity.


The Deprivation of Liberty Safeguards (DOLS) is a legal framework to prevent breaches of the European Convention on Human Rights (ECHR) when it comes to the deprivation of liberty for those aged 18 or above, in either a care home or hospital. It is a complex area and more information can be found in chapter six of the MCA Code of Practice.

It was set to be replaced by the Liberty Protection Safeguards (LPS) but the implementation of this has been delayed. You can read more about Deprivation of Liberty Safeguards here.


Part of the best interests' process is to consider the views of others who are close to the patient, including carers, as well as the views of any attorney or deputy, and anyone named by the patient to be consulted, while not breaching confidentiality.

If there are no such people and the decision to be made relates to a major medical intervention, then an independent mental capacity advocate (IMCA) must be involved. IMCAs support and represent those who do not have anyone else to support them. They do not, however, make decisions on behalf of the patient.

Office of the Public Guardian (OPG)

The Office of the Public Guardian supervises and keeps a register of deputies, lasting powers of attorney and enduring powers of attorney, checks on what attorneys are doing, and investigates complaints about attorneys or deputies.

This page was correct at publication on 14/09/2023. 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.

Dr Ellie Mein MDU medico-legal adviser

by Dr Ellie Mein Medico-legal adviser


Ellie joined the MDU as a medico-legal adviser in 2013. Prior to this she worked as an ophthalmologist before completing her Graduate Diploma in Law in Birmingham.