Mental capacity and best interests

March 5, 2021
September 1, 2023

By Jane Stanfield, Associate Practitioner

The Mental Capacity Act 2005 has five fundamental principles:

1. A person must be assumed to have capacity to make decisions. Before they can have a decision made by someone else on their behalf, their capacity needs to be assessed. (This means that it must not be assumed that a person with dementia cannot make a decision for themselves just because they have dementia)

2. All practical steps must be taken to help the person to make a decision

3. An unwise decision does not necessarily indicate a lack of capacity – we all make unwise decisions sometimes

4. Any decision made on behalf of a person when they do not have capacity must be made in that person’s best interests

5. Any decision made must be the least restrictive option

Mental Capacity is assessed in relation to a specific decision; a person with dementia may have the capacity to make some decisions but may lack capacity for other decisions.

To assess whether the person has capacity or not the following questions need to be asked:

Does the person have an impairment of the mind or brain? 

This could be a dementia, learning disability, brain injury, influence of alcohol or drugs or other impairment.  If there is no impairment then they do not lack capacity.

If there is an impairment, are they still able to do all of the following four actions?

1. Understand the information relevant to the decision? (whether by talking, using sign language or any other means)

2. Retain that information for long enough to weigh it up?

3. Understand the consequences of making or not making the decision?

4. Communicate their decision? (whether by talking, using sign language or any other means)

If the answer is “no” to one or more of these then the person does not have capacity to make the decision.

There is no one particular person whose job it is to decide whether a person has capacity to make a decision. It might be a family carer or a hospital team, but for each decision, all of these questions need to be asked.  

If someone has been assessed as lacking mental capacity for a decision then a decision in their best interests must be made.

To make a best interest decision the decision maker must:

Formal best interest decisions are often made when social and health care professionals meet with the person who lacks capacity and/or their family members, and sometimes an advocate for the person.  These are called Best Interest Meetings.  In these circumstances the reasons for the decisions must be documented. 

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Mental capacity and best interests
We explore the five fundamental principles of the Mental Capacity Act 2005 and its impact on carers
Legal rights