How to apply the Mental Capacity Act - medico-legal

Capacity is specific to the treatment or test, explain Dr Mark Jopling and Dr Matthew Dewsbery.

Even experts can disagree as to whether a patient has capacity
Even experts can disagree as to whether a patient has capacity

Assessing a patient's mental capacity is an essential skill for GPs. It empowers doctors to make decisions in their patient's best interests when the patient lacks capacity. It also protects patients with capacity from having their legitimate wishes ignored.

The legal framework for capacity assessments in England and Wales, the Mental Capacity Act (2005), applies to everyone over 16 years old.

Whenever you make a decision for a patient, you must establish the following:

  • The patient lacks capacity.
  • You are acting in their best interests.
  • There is no lasting power of attorney in place.

Where there is disagreement or uncertainty, cases will go to the Court of Protection.


For a patient to be deemed to lack capacity, they need to meet both of the following criteria:

  • They have an 'impairment of their mind'. This includes learning disabilities, dementia, delirium, brain damage, mental illness and alcohol or drug use.
  • They have an impaired ability to make a specific decision. To have capacity to make a decision, a patient needs to:
  • Understand the information they have been given.
  • Retain that information, although only long enough to be able to make an 'effective decision'.
  • Weigh up the information.
  • Communicate their decision.

There should be an assumption of capacity and you must make every effort to help the patient achieve the four areas outlined above.

For example, information should be provided in a way that is easy to understand and retain, and patients may need writing materials or an interpreter to help them express their views.

A patient can have capacity to decide on one intervention but not another, and their capacity can change over time.

The Act stresses that an unwise decision does not equate to a lack of capacity.

Case study - Refusing treatment after an overdose

A prison GP is called to see a patient who has taken an overdose of sodium valproate tablets he has been hiding in his cell. He is drowsy and cannot answer the doctor's questions coherently, but he clearly expresses that he does not want to be taken to hospital.

He has a diagnosis of an emotionally unstable personality disorder and has tried to kill himself before.

Toxbase confirms that his overdose is potentially lethal.

When assessing the patient's capacity, the doctor finds that he is unable to understand, weigh up or retain the information that he is given, because of his reduced level of consciousness. There is no evidence of an advance decision or that when he had capacity, he would have declined treatment, so the doctor decides to admit him to hospital despite his verbal request to be allowed to die.

Learning points

Where someone lacks capacity and you are acting in their best interests, try to establish what wishes they had previously expressed. This may be documented or verbal. You have to decide how reliable this information is and whether the patient had capacity at the time of expressing those wishes.

All doctors should be able to make an assessment of capacity and in an emergency, act immediately on their assessment. The Mental Capacity Act would support you in providing immediate life-saving treatment in cases where the patient's capacity is uncertain or when the patient's prior wishes are not clear.

Best interests

According to the Act, 'an act done, or decision made, under this Act, for or on behalf of a person who lacks capacity must be done, or made, in his best interests'.

'Best interests' are not defined in the Act itself, but the following areas should be considered and this information weighed up:

  • The patient's past wishes or previous instruction, for example an advance directive.
  • Input from the patient, however limited.
  • What the patient's beliefs suggest they would have wanted.
  • Input from relatives and friends. Their role is to help establish what the patient would have wanted when they had capacity, not to give their opinion on the intervention being proposed.
  • Whether the patient may regain capacity - could the decision wait until then?
  • Avoid making assumptions or imposing your personal views.
  • Consider the 'least restrictive option' - the option that will have the least impact on the patient.

Advance decision

Advance decisions are made when the patient has capacity. They can be overridden by contemporary decisions (provided the patient has capacity).

They legally bind doctors not to provide stated treatments. They do not legally bind doctors to provide specific treatments. Only patients over the age of 18 years can make an advance decision.

Independent mental capacity advocate

An advocate is required for the following interventions in which doctors may be involved:

  • Serious medical treatment is being proposed or stopped.
  • Long-term care decisions are being made.
  • Vulnerable adult protection cases.

An advocate is only necessary if a patient lacks capacity and is 'unbefriended'. This means that there are no family or friends available or capable of representing the patient.

Lasting power of attorney

This is someone nominated by the patient (when they have capacity) to make decisions on their behalf regarding health, welfare and financial decisions. They can only refuse life-sustaining treatment if the patient has specified this power. Only people over the age of 18 years can make a lasting power of attorney.

Lasting powers of attorney are regulated by the Office of the Public Guardian.

Case study - Refusing investigations for a necrotic foot

A 50-year-old woman complains to her GP of pain in her right foot. She has a past history of a psychotic episode and is taking olanzapine. Her notes also mention that she has a learning disability.

Her right big toe is dusky coloured and necrotic at the tip. Suspecting ischaemia, the GP arranges a same-day review with the vascular team.

They tell the patient she will need an angiogram and it is possible she may need an amputation. Terrified, she refuses to see them again, despite the GP's attempts to persuade her to do so.

After a number of home visits, the GP begins to doubt her capacity with regard to refusing the vascular investigations.

She can repeat back the process of investigation and treatment that she requires and the risks of not having treatment, but when the GP sees her again, she reverts to her original belief that her foot can be made better with antibiotics. Her refusal of treatment is based on her fear of being 'cut open'.

Her foot becomes increasingly necrotic and the GP arranges an urgent psychiatric assessment of her capacity. The psychiatrist sees her and feels that she has capacity to decline further vascular review at this time. The GP is unhappy with this decision and requests another psychiatric review, with a view to the case being referred to the Court of Protection. Before this assessment is carried out, the patient dies suddenly of a pulmonary embolism secondary to a DVT.

Learning points

Capacity is specific to the treatment or investigation in question. Although a diagnosis of psychosis and learning disability may be an 'impairment of mind' that causes someone to lack capacity, these diagnoses themselves do not prove a patient lacks capacity.

In assessing capacity, you need to establish that the patient can retain the information long enough to make an 'effective decision.' Short-term memory deficits do not preclude a patient from having the capacity to make a decision.

When considering treating a patient against their will, a second opinion from someone experienced in capacity assessments (for example, a psychiatrist or geriatrician) may be prudent. 'Benign force' can be used to facilitate treatment for someone who lacks capacity.

There can be disagreement, even between experts, as to whether a patient has capacity. In a recent case that went to the Court of Protection, the judge ruled that the patient had capacity to request an abortion. The patient's psychiatrist had been '100% certain' that she lacked capacity to make a decision about a termination.1


  • Dr Jopling is a GP in London and Dr Dewsbery is an ST5 in forensic psychiatry, Birmingham and Solihull Mental Health Foundation Trust
  • Dr Jopling is guarantor for the content



1. Woman with bipolar disorder can abort her baby, judge rules. BMJ 2013; 346: f3387.

Have you registered with us yet?

Register now to enjoy more articles and free email bulletins


Already registered?

Sign in

Follow Us:

Just published

Medico-legal: Intimate examinations and chaperones during COVID-19

Medico-legal: Intimate examinations and chaperones during COVID-19

Remote consultations are likely to be a key part of general practice for months to...

NHS England promises detail on additional flu funding ‘by end of August’

NHS England promises detail on additional flu funding ‘by end of August’

GPs may have to wait until the end of August to find out details of any additional...

Why 63% of GPs expect to do more home-working after COVID-19

Why 63% of GPs expect to do more home-working after COVID-19

Working from home was one of the key issues raised in GPonline's survey of more than...

Lack of support during the menopause leading female doctors to quit

Lack of support during the menopause leading female doctors to quit

A lack of support during the menopause has led some female doctors to consider reducing...

One in three single-handed GPs at high-risk from COVID-19

One in three single-handed GPs at high-risk from COVID-19

A third of single-handed GPs are at high-risk from COVID-19, which could potentially...

Viewpoint: PCNs can be at the forefront of tackling health inequalities

Viewpoint: PCNs can be at the forefront of tackling health inequalities

Dr Mark Spencer explains how the COVID-19 pandemic helped his primary care network...