Mental capacity & professional negligence

For a will to be valid, the person who makes the will must have sufficient mental capacity. “Testamentary capacity” is the legal term used to describe a person’s legal and mental ability to make or alter a valid will. 

If the person making the will lacks this capacity at the time that the will is executed, the will is invalid. 


How is capacity to make a Will assessed?

There have been lots of cases in which mental capacity has been used as the basis to challenge a will. It is becoming increasingly common given that our population is aging and people and living longer. It has also increased due to the number of people who suffer with Alzheimer’s, dementia and other illnesses associated with old age.   

The correct test for assessing whether a testator had capacity to make a will remains as set out in the 19th century case of Banks v Goodfellow (1870) and is: 


“It is essential to the exercise of such a power that a testator shall understand the nature of the act and its effects; shall understand the extent of the property of which he is disposing; shall be able to comprehend and appreciate the claims to which he ought to give effect with a view to the latter object, that no disorder of the mind shall poison his affections, pervert his sense of right, or prevent the exercise of his natural faculties – that no insane delusion shall influence his will in disposing of his property and bring about a disposal of it which, If the mind had been sound, would not have been made”. 


Therefore, in order to make a valid Will, the person who made the Will must: 


  • Understand the nature and effect of making a Will;
  • Understand the extent of his Estate;
  • Comprehend and appreciate the claims to which he ought to give effect; and
  • No disorder of the mind shall poison his affections, pervert his sense of right, or prevent the exercise of his natural faculties.


Therefore if it is believed or there is a concern the person who made the will was unable to comprehend any or all of the above points, there could be grounds to challenge whether their will is valid or not.  


Will writing and negligence relating to capacity

  • There has been an increase in Will Disputes relating to mental capacity due to aging population and increase in Dementia and Alzheimer’s cases as set out above 
  • Best Practice is for a professional (be it a lawyer or will writer or any other professional undertaking such work) to follow the “Golden Rule” which is an informal guide to making sure elderly or vulnerable client’s are properly protected when giving such important instructions 
  • It is important to establish if you think a family member or friend may have made a will they were incapable of understanding that they were seen by the professional alone – this is part of the “Golden Rule” criteria and seeks to ensure the person detailed their wishes of their own free will and with the assistance of another person guiding them or speaking for them  
  • It is important that the professional should keep a detailed note of what was discussed. This should include details such as – what assets does the person have? Full details of family members and historic family details as well as clear discussion as to why they wish to change/make a Will. If an attendance note is vague and without recording much detail it is difficult to establish what steps were take to ensure the deceased knew what their estate entailed and what the implications of making a will would be 
  • If there are any capacity concerns ie with a very elderly client or someone who has been diagnosed with an early onset disease, a professional should ideally request a certificate of mental capacity from the client’s GP before undertaking instructions 


If a professional has failed to properly take into consideration and assess a person’s mental capacity and allowed them to execute a will then their may be potential grounds for professional negligence. This generally if there is no other recourse to put right the problems that arise from the will being made in the first place.  


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