The Mental Capacity Act 2005 (MCA) is a piece of legislation that applies in England and Wales. It provides a legal framework for making decisions on behalf of individuals aged 16 or over who lack the mental capacity to make specific decisions for themselves. The Act aims to empower individuals to make their own decisions wherever possible, and to protect those who cannot.

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A crucial aspect of the MCA is that the assessment of capacity is time-specific and decision-specific. This means:

• Time-specific: A person's capacity can fluctuate. Someone might lack capacity at one point in time (e.g., due to acute illness or intoxication) but regain it later. Therefore, capacity must be assessed at the time the decision needs to be made.

• Decision-specific: A person might have capacity to make some decisions but not others. For example, they might be able to decide what to eat but lack the capacity to manage complex financial affairs. Capacity is not a blanket concept; it relates to a particular decision at a particular time.

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The main principles of the Mental Capacity Act 2005 are:

1. Presumption of Capacity: It must be assumed that a person has capacity unless it is established that they lack it. This means you should not assume someone lacks capacity just because they have a particular condition or disability.

2. Support to Make Own Decisions: A person is not to be treated as unable to make a decision unless all practicable steps to help them to do so have been taken without success. This includes providing information in an accessible format, using visual aids, or allowing more time.

3. Unwise Decisions: An unwise decision does not mean a lack of capacity. A person is not to be treated as unable to make a decision merely because they make an unwise decision. People have the right to make choices that others might consider eccentric or risky.

4. Best Interests: An act done, or decision made, under this Act for or on behalf of a person who lacks capacity must be done, or made, in their best interests. This is a core principle, requiring consideration of all relevant circumstances and the person's wishes and feelings.

5. Least Restrictive Option: Before an act is done, or a decision made, under this Act for or on behalf of a person who lacks capacity, regard must be had to whether the purpose for which it is needed can be as effectively achieved in a way that is less restrictive of the person's rights and freedom of action. This means considering alternatives that intrude less on the person's life and liberty.

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In essence, the MCA is designed to ensure that decisions are made with the individual's dignity and autonomy at the forefront, only intervening when absolutely necessary and always in their best interests, whilst being as unrestrictive as possible. The time and decision-specific nature of capacity assessments reinforces the individualised and person-centred approach of the Act.