Capacity and Wills

Written by Richard O'Shea, Solicitor TEP · Mary Molloy Solicitors, established 1981 · Last reviewed 21 August 2026

The test for making a will

Testamentary capacity follows the long-established Banks v Goodfellow formulation: the testator must understand the nature of making a will and its effects, the extent of their property in broad terms, and the claims of those who might expect to benefit — and no disorder of mind may poison their affections or pervert their sense of right in the disposition. It sits alongside the 2015 Act's framework rather than being replaced by it, and like all capacity it is time- and decision-specific: capacity on the day of instructions and execution is what counts.

Early dementia does not end will-making

A diagnosis is a flag for care, not a bar. Wills made in early dementia stand where capacity is properly assessed and documented — and fall where it wasn't, years later, when nobody can remake the evidence. Careful practice looks like: instructions taken from the testator alone; the solicitor alert to influence around them; where age or diagnosis raises the question, a contemporaneous medical assessment of testamentary capacity (the practice known as the "golden rule" — prudence, not law, but prudence that wins cases); and an attendance note that records understanding in the testator's own words. That file is the will's armour.

Challenges after death

Capacity is the workhorse ground for challenging wills, alongside undue influence and want of knowledge and approval. The pattern in the case law is consistent: outcomes follow the quality of the contemporaneous evidence — the drafting solicitor's file, the medical notes, the circumstances of instructions. Which is why the cheap will made in a hurry, unwitnessed by any assessment, can become the most expensive document a family ever fought over.

Where this practice fits

Will drafting itself sits with our main practice at marymolloysolicitor.ie — this site's role is the capacity layer: planning the timing after a diagnosis (the after-diagnosis guide), arranging robust capacity assessment around instructions, and advising executors and families when a will's validity is questioned. If a will fight is brewing in your family, the time for advice is before positions harden.