About Mental Capacity

What is Mental Capacity?

To have mental capacity means being able to make decisions for ourselves. We all make decisions, big and small, every day of our lives and most of us are able to make these decisions for ourselves, although we may seek information, advice or support for the more serious or complex ones. 

Having mental capacity means that we can

  • Understand information given to us and
  • Weigh up the information available to make that decision and
  • Retain that information long enough to be able to make a decision and
  • Communicate our  decision to others

The law requires that we have mental capacity when making certain decisions in our life, in order for them to be considered valid.  These include making a will, consenting to medical treatment or appointing someone else as our decision maker for the future (ie making an advance directive).

The Law Society of South Australia has produced a Statement of Princples with Guidelines relating to client capacity which may further assist to understand the complexity of mental capacity considerations.

What is Mental Incapacity?

Having a mental incapacity means not being able to make some decisions even after the necessary information, advice and support has been given to assist. Capacity to make a particular decision will be in doubt if a person -

  • does not understand the information given or
  • cannot consider the main issues options and likely consequences involved in making that decision or
  • does not remember that information long enough to be able to make a decision or
  • cannot communicate the decision to others

Alternative terms are used to describe mental incapacity.  These include "mental impairment” and “decision making incapacity”. These terms usually have their origins in legal statutes which offers their own definition of the terms. The term "mental incapacity" is used in the Guardianship and Administration Act 1993.

How will I know whether a person has a  mental incapacity?

Generally individuals who have a mental incapacity have some form of underlying medical condition or disability which affects thinking, reasoning and/or memory.   Examples might be conditions existing from birth (eg intellectual disability), brain damage from illness or trauma (eg dementia, stroke or from a motor vehicle accident) or mental health issues (eg a psychotic illness). 

Most people who have medical conditions or disabilities are however able to make their own decisions. Some people will require extra support to do this.  This support can include assisted decision making or supported decision making.

Mental Incapacity is decision specific

Mental incapacity may be temporary or ongoing or may only affect certain decisions. Capacity to make a decision can therefore change depending on what the decision is, the complexity of the issues involved in the decision and when the decision is to be made.    Because of this it is said that mental incapacity is “decision specific”.

For example

  • a person may not understand their financial affairs and forget to pay their bills but still be able to make decisions about their health care
  • a person may have a mental illness which temporarily affects their ability to manage their finances when they are unwell
  • a person may know what it is to take headache pills but not understand the complexity of dialysis treatment for kidney disease and so not be able to give effective consent for this treatment 

Even where some form of cognitive difficulty has been confirmed an individual should be given the opportunity to make their own decision on each occasion, as that person may have the capacity to do so at that particular time.

Who decides whether or not someone can’t make their own decisions/ has a mental incapacity?

Sometimes this occurs through a natural process - for example, where family members gradually take over decision making responsibilities for a mentally frail elderly relative and that person agrees to the help being provided. However formal assessment may be required particularly for legal processes or where there are differences of opinions about what is happening. 

As most incapacities are medical in their origins, doctors are asked to provide reports regarding capacity.  This may be a general  practitioner or a doctor who specialises in mental functioning such as a neurologist, geriatrician or psychiatrist.  Clinical and neuro psychologists also have specialist skills in assessing mental functioning.  Other health professionals and service providers may have useful observations regarding day to day functioning of the person as well.

Mental Incapacity and the SA Guardianship and Administration Act 1993 (GAA)

 For the purposes of the operations of the GAA a particular definition of mental incapacity applies and these conditions must be met before the Guardianship Board can consider making orders or decisions under the Act.  This is

‘...the inability of a person to look after his or her own health, safety or welfare or to manage his or her own affairs, as a result of-

(a) any damage to, or any illness, disorder, imperfect or delayed development, impairment or deterioration, of the brain or mind; or

 (b) any physical illness or condition that renders the person unable to communicate his or her intentions or wishes in any manner whatsoever.’