As the UK population continues to age, disputes involving testamentary capacity are becoming increasingly common. According to recent estimates, around 982,000 people in the UK are currently living with dementia, a figure expected to rise to 1.4 million by 2040.

At the same time, probate litigation is on the rise. Litigation intelligence provider Solomonic reported that the final quarter of 2025 saw the highest number of probate claims issued in the High Court in the last decade, with approximately 40% of those claims involving allegations that the deceased lacked the mental capacity to make their will.

Despite this trend, the courts have consistently emphasised an important principle: a diagnosis of dementia does not automatically mean a person lacks the capacity to make a valid will.

The law requires courts to consider whether an individual had the ability to understand the nature and effect of their will at the time it was made. The focus is not on whether a medical condition existed, but on how that condition affected the person’s decision-making at the relevant moment.

This distinction was reinforced in two recent cases. In Parfitt v Jones & Wilkes, a daughter argued that her mother’s diagnosis of progressive dementia meant she lacked capacity to execute her will. The court rejected the claim, emphasising that capacity can fluctuate, even where cognitive decline is present.

Similarly, in Scott v Scott, a challenge based on the testator’s diagnosis of fronto-temporal dementia also failed. After reviewing detailed attendance notes, medical records and expert evidence, the court concluded that the testator retained the necessary capacity when the wills were made.

These decisions highlight a consistent judicial approach: dementia is a relevant factor, but it is not determinative. What matters is whether the individual could understand, weigh and communicate the decisions required to make their will at the time they gave instructions and signed it.

As a result, the quality of the available evidence is becoming increasingly important. Solicitors are placing greater emphasis on detailed attendance notes, careful record-keeping and, where appropriate, obtaining contemporaneous medical opinions. These steps can help demonstrate that a testator understood their decisions and reduce the likelihood of a successful challenge later on.

With dementia diagnoses expected to rise significantly over the coming decades, disputes concerning testamentary capacity are likely to remain a prominent feature of contentious probate litigation. The key question for the courts will continue to be not whether a person had a diagnosis, but whether they retained the ability to understand and give effect to their wishes when it mattered most.

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