Cluver Markotter

Cognitive impairment and making a will

A person with some cognitive impairment may be incapable of making a will at some times, but of sound mind at other times.  The general presumption is that a person who made a will, was of sound mind and understood the consequences of the document signed at the time. The key question is the person’s mental capacity when executing the will.


A person diagnosed with Alzheimer’s, for example, may at the early stages of the disease have the requisite mental capacity at some times, but not at other times. In the early stages of this disease, it is quite common for someone to lack capacity one day and to have it the next. On principle Alzheimer-sufferers can validly execute a will at times when they can understand its nature and effect, but if the testator’s mental capacity is in contention, a prior Alzheimer-diagnosis may impact on the evaluation of evidence indicating lack of mental capacity. The person alleging cognitive impairment must prove on a balance of probability that the testator lacked capacity at the time of executing the will.


The principles of testamentary capacity are based on the common-law requirements namely (i) that the testator must have reached the age of 16 years, and (ii) the testator must be of sound mind at the time of execution i.e., the testator must have the necessary mental capacity to understand the nature and effect of the act they are about to complete.


To establish whether a testator had the capacity to understand the act of executing a will, the test set out in Banks v Goodfellow (1870 LR 5 QB 549) , is whether the testator: (i) understood the nature and effect of a will; (ii) had knowledge of the nature and extent of property owned and bequeathed in terms of the will; (iii) are aware of the persons for whom they would usually be expected to provide; and (iv) was not suffering from a disorder of the mind or insane delusion that would result in an undesirable disposition. In the event of any doubt that the testator meets any one of these requirements, a legal advisor should advise against execution of the purported will.


The deciding moment for establishing the competence of a testator is the time when the will was made and not when instructions were given to draft a will. Therefore, if the testator who suffers from Alzheimer’s disease, for example, is temporarily of sound mind, the document would be valid. However, in this situation it is advisable to take extra care to record the evidence of capacity at the time the will is executed, to avoid any uncertainty afterwards.


Medical evidence such as psychiatrist reports, witness statements and depositions can be used in support of establishing testamentary incapacity. Should the testator already have been declared of unsound mind prior to making the will, and if the validity of the will is then challenged, the beneficiary alleging that the testator was of sound mind, would have to prove that the testator did, in fact, have a clear or lucid interval while making the will.

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top