What is Capacity?

A person is said to have the mental capacity to make a decision when they can: 

• understand the information and choices presented to them;

• weigh up the information to determine what the decision will mean for him or her; and

• then communicate their decision.

In NSW, the law assumes that everyone has the mental capacity to make their own decisions.  However, sometimes a person may not have the capacity or ability to make decisions.

When could a person’s capacity be affected? 

A person’s capacity to make decisions may be affected temporarily, for example because of illness or the effects of medication.

A person’s mental capacity may also be affected permanently because of conditions such as intellectual disability, dementia, or brain injury.   

Capacity is decision specific, which means that the level of capacity required to make a decision will vary depending on the type of decision the person needs to make.

Examples Tom has dementia and is capable of making simple decisions about spending money on shopping.  However, Tom finds it difficult to concentrate and remember details, so he does not have the capacity to make decisions about investing his superannuation. Mary has an intellectual disability. She knows that taking tablets will make her cough go away, so she has the capacity to consent to antibiotics.  However, Mary cannot consent to having surgery because she does not have the capacity to understand all the complications, risks and side effects.

What if you have concerns about a person’s capacity?

Although we start off assuming that everyone has capacity, sometimes a person’s behaviour might lead us to have doubts about their capacity. For example, a person no longer remembers the name of common objects, or constantly forgets the name of someone close to them.

It is important to explore the reasons why a person appears to have impaired capacity.  Do not assume that because a person has memory problems or a disability that they lack capacity to make decisions.  Also, a person may have an eccentric lifestyle or make personal decisions that we do not agree with, but this doesn’t mean that they do not have capacity. 

When there is a question or disagreement about a person’s ability to make their own decisions, an assessment can provide evidence about the state of a person’s capacity. A capacity assessment could be made by a health professional, such as a psycho geriatrician or neuropsychologist.  When assessing a person’s mental capacity it is important to remember that what is being assessed is their capacity to make a specific decision at that point in time. 

You can get a copy of the Capacity Toolkit, from the Diversity Services Unit of the Department of Attorney General and Justice, phone 02 8688 8460 or 02 8688 7507.  You can also go to their website for a copy of the Capacity Toolkit, and fact sheets in English and other languages.

The NSW Law Society also has extensive notes and references on mental capacity.