In order to make a valid will, you have to have capacity to understand what you are doing – to be able to properly weigh up the decisions that you are making and their effects.  The test for capacity is set out in the case of Banks v Goodfellow (1870):

  1. the testator must understand the nature of his act and its effects;
  2. he must appreciate the extent of his estate;
  3. he should be able to comprehend and appreciate the claims which he should give effect to;
  4. in relation to (c), nothing shall poison his affections, pervert his sense of right or bring about a disposition that he would not have made had he been of sound mind.

After someone's death, it can be difficult to assess whether they had capacity at the time of making their will.

One factor which is often used as evidence of incapacity is where someone is suffering from dementia.  Dementia is a progressive condition, and may have a profound effect on someone long before they are formally diagnosed but it can also leave people having good days and bad - lucid intervals where their decision making ability is unaffected.

In the recent case of Simon v Byford and others [2013] EQHC 1490, the Court held that Mrs Simon had testamentary capacity even though she was suffering from mild to moderate dementia at the time of making her will.  She had made an earlier will leaving more to one of her four children than the others and evidence was given that this was to 'even things up' between the siblings.  One had contributed more to the success of the family business than the others and the others had been assisted financially by the testator during her lifetime.  She set this out in a side letter to her will.

Her final will was made at her 88th birthday party - an event where two of her children were present but not the one who had previously been bequeathed more of her estate than the others.  The new will was typed up and signed that evening and left her estate in equal shares to her children.  The judge found that she was unlikely to have been able to remember the provisions of her earlier will, or the reason for preferring one of her children in it.  However, crucially she was capable of understanding the provisions of her will, which was a simple document.  The fact that she could not necessarily remember the provisions of the earlier will and side letter did not mean that she did not have capacity and nor did the fact that she was suffering from dementia. 

The question is what a person is able to understand and appreciate at the moment when they make their will - someone with dementia may have bad days when they lack capacity, and good days when they do not.  The Judge placed great reliance on the witnesses who were at the birthday party (which made things difficult for the Claimant as he was not there), as they were the ones who could attest to the deceased's capacity at the crucial time.

Capacity cases are frequently difficult to prove as they require the Court to make a complex factual decision without being able to assess the person in question.  Frequently they are asked to rely on the evidence of an expert who has never met the person either.  Given that people are increasingly living for prolonged periods whilst suffering from dementia, and that it can go undiagnosed for a long time, it is likely that capacity claims will increase.