Testamentary capacity is a key attribute to the validity of any will. As a general rule, individuals making a will should have sufficient mental capacity in order to do so, as prescribed by case law. Specifically, they need to understand the effects of their will and its contents; be able to comprehend and appreciate relevant claims; and not have any mental disorder that affects their sense of right or interferes with their capacity for decision making. Furthermore, the level of understanding needed varies according to the complexity of the will, assets being disposed and potential claims upon them. Understanding these laws is essential before creating a legally binding document.
The Mental Capacity Act 2005, which took effect "on 1 October 2007 (Gazette issue 57613), introduced some confusion as to whether the common-law test provided for in Banks v Goodfellow was rendered obsolete. This is further compounded by the code of practice attached to the act, which states that its definition of capacity is 'in line with the existing common law tests and does not replace them' - but also that judges may decide to use it ‘if they think it is appropriate'.
The Mental Capacity Act (2005) and case law lay out different stipulations regarding a testator's capacity to make a valid will. Firstly, the MCA test assumes capacity unless proved otherwise; on the other hand, to dispute this fact in a common law setting only requires that the "real doubt" must be raised first before any burden of proof is shifted. Secondly, the MCA stresses understanding the relevant information required for making a decision, including foreseeing potential outcomes. This differs from what case law mandates which is simply comprehending claims to consider when creating a will. An example of this situation can be found in Simon v Byford (2014) wherein it was ruled that not understanding collateral consequences does not invalidate one's will at common law.
The test for testamentary capacity has been long established and clarified in the ruling of Walker v Badmin (2015), which stipulated that Banks v Goodfellow is 'the correct and only test'. The Mental Capacity Act was never intended to supersede this ruling; rather, its goal is to provide an arbitration foundation for decisions regarding living persons who lack the ability to make legal agreements.
Given the already-low threshold for testamentary capacity set by case law, practitioners must bear in mind that assessing cognitive ability should extend beyond one's actual understanding. Memory alone does not determine capacity; while a poor memory may inhibit clear comprehension, it cannot be used as substantial proof against a determination of capacity. A person can choose not to assess the information presented before them but still retain a level of functional understanding sufficient for contractual agreements. All these factors should be taken into account when evaluating a testator's eligibility for making legal documents.