When a person lacks mental capacity, they are unable to create any valid legal agreement – for example to make a valid will. Challenges to wills on the ground that the testator lacked mental capacity are becoming increasingly common, especially when the will was made (or an existing will was changed) by someone of advanced years.

When it is feared that mental capacity may be lacking, it is possible for a test to be carried out to confirm the extent of a person's ability. The test involves two stages.

The first identifies whether there is an impairment of mental functioning which is sufficient to affect the ability of the person making the decision that is in point (e.g. making a valid will).

The second stage involves four further tests, which must all be satisfied to show that the person has mental capacity:

• The person must be able to understand information relevant to the decision being taken;
• The person must be able to retain that information for a period of time sufficient for them to make the decision;
• The person must be able to evaluate the information relevant to the decision being made; and
• The person must be able to communicate their decision.

If you are concerned that a family member may be losing mental capacity and there are 'loose ends' which should be tied up (such as creating a will or executing a power of attorney), it is important to make sure these matters are dealt with before mental capacity is lost.