The ability to make decisions (and thereby its assessment) can be complex. It may be affected by a combination of factors that vary between individuals. Even when cognitive functioning may be compromised (for instance, by dementia), a person may still be able to express important deep-rooted values underpinning their decisions. The circumstances may demand that these different elements are explored in greater or lesser detail in making conclusions about an individual’s decision-making capacity. This may add to the complexity of an assessment. From the outset, to make an adequately informed treatment or other decision, you must have sufficient information, be able to make the decision free from coercion and have mental capacity.

Notwithstanding the challenges, with appropriate thought, preparation and attention to documentation, it should be possible to record a legally defensible assessment of capacity for most situations that arise in clinical practice. The purpose of this chapter is to provide an accessible approach to capacity assessment and its recording.

The Mental Capacity Act (MCA) 2005 came into force in 2007 and covers England and Wales. It provides a statutory framework for anyone over the age of 16 who lacks capacity to make decisions for themselves, for whatever reason. The MCA was drafted by the Law Commission partly in response to the increased prevalence of dementia and the lack of legislation to deal with the challenges of so many people living longer and losing their ability to make decisions. It is the loss of ability to make decisions, because of the disease, which makes the key link between providing care and treatment with the application of the law. This is why the MCA is perhaps the most important of all the pieces of legislation we consider. The practical applications of the Act will be dealt with in more detail in the chapters to follow. More detailed guidance can be found in the Mental Capacity Act 2005: Code of Practice (for England and Wales), revised in 2022. We include some of the main amendments to the Code at the end of this chapter and these are also covered in the relevant sections of the book.