Assessment of capacity

A person is considered to have capacity to make a decision if they are able to do all four of the following:

to understand the information relevant to the decision

to retain that information

to use or weigh that information as part of the process of making the decision

to communicate any decision (whether by talking, using sign language, writing, or any other means).

Figure 1 shows an imagined conversation between a doctor and a person who is considering whether to go ahead with treatment as advised and illustrates the factors that demonstrate capacity.

Fig. 1 A person with capacity to decide about treatment for high blood pressure.

It is important to remember when carrying out assessments of capacity that someone may have the capacity to make some decisions, but not others. For example, a woman with dementia might be able to remember details of two nursing homes for long enough to choose which she would prefer, but might not be able to weigh up the risks and benefits of chemotherapy for breast cancer. A man with delusional disorder who believed that his teeth were being used by the government to transmit signals to aliens would probably not have capacity to make decisions about his dental care but might be fit to make choices about other aspects of his health.

The five principles of capacity

The Mental Capacity Act describes five principles that should guide all work in this area – these are summarised in Figure 2. If you don’t apply these principles to the assessment of capacity and to decisions concerning people who lack capacity in England and Wales, then you will be breaching people’s statutory rights.

Fig. 2 The Five Principles of Capacity.