Mental Capacity Law

Mental Capacity Law

Mental capacity can be broadly understood as the ability to make decisions. The capacity required to make a decision will depend on the decision in question: the more complicated a decision is, the higher the level of capacity that will be expected of the person to make that decision.

While people who have mental disorder may also lack mental capacity, these are two separate matters which are assessed differently. This means that a person who has a mental disorder may still retain the ability to make decisions, and should not automatically be presumed to lack capacity. This is in line with the presumption of capacity at common law, which means that every person is assumed to have capacity until it is proven that they do not.

As for how capacity is assessed, the Mental Health Ordinance (MHO) contains tests for different contexts. For example, in the context of property and affairs, the test for capacity is whether the person is incapable of managing and administering his property and affairs. For those who do not have any mental disorder or impairment, the test for capacity will be the one at common law. This test, taken from the leading case of Re C, asks whether the person:

1. can understand and retain (in other words, remember) the treatment information;
2. believes that information; and
3. can weigh that information to make a choice.

A person who lacks mental capacity is defined as a ‘mentally incapacitated person’ (MIP) under the MHO.