Why multi-million estates are crumbling to dementia, age claims

When an elderly person signs their will, few imagine that declining memory or serious mental illness could later destroy those final wishes.

Yet that is exactly what happens in courts across the country, sometimes years after death, when aggrieved beneficiaries challenge the document purporting to be the testator’s last wishes.

Age, dementia and other ailments do not automatically void a will, but they shift a heavy burden onto those defending it, forcing them to prove the testator’s mind was sound at the moment of signing.

A look at several recent High Court rulings shows just how fragile testamentary intent becomes when mental capacity wavers.

Judges across the country have continually faced a delicate question: should old age and failing minds override what is written in black and white?

A vivid illustration is the fight over the estate of the late Gakinya Kariuki, alias John Gakinya, estimated to be worth over Sh50 million, recently determined by the High Court in Thika on November 21, 2025.

In that case, the court did not merely tweak a will; it completely demolished it, declared the estate intestate, and issued a chilling warning to families, lawyers and executors who ignore capacity and mental health.

The late Gakinya died on December 28, 2021, aged about 85. A widower from Kiamwangi in Gatundu South, he left behind several children, among them two sons: Raymond Kariuki Gakinya (the appellant) and Joseph Kimani John Gakinya (the respondent and named executor).

He also left five daughters: Mary Njoki Kiguru, Regina Wairimu, Alice Wanjiku Muchiri, Lucy Wathoni Ngwiri and Eunice Wangui Gakinya.

Their mother, Emily Wambui Gakinya, had predeceased their father on October 22, 2014.

At the heart of the dispute was a written will dated February 19, 2021, drawn by an advocate and executed by thumbprint.

It appointed Joseph as sole executor and listed eight beneficiaries together with six multi-million-shilling assets in Juja, Kiambu County.

Conspicuously absent from this list—but central to the dispute—were Antony Njoroge Gakinya, who claimed to be a son of the deceased, and Fidelis Wairimu Ruge, who claimed to be his daughter from a customary marriage to Hanna Barabiu.

Also involved was a grandson, Simon Gakuha Muhoho, representing the estate of his late mother, Jane Njeri Muhoho, a deceased daughter of the testator.

On paper, the will ticked all the formal boxes. But it divided the estate in a way some family members insisted their father would never have done if he had been in his right mind.

They said that by the time he signed the document, age and illness had eroded his mental capacity.

After his death, Joseph petitioned the Chief Magistrate’s Court in Gatundu for a grant of probate on September 9, 2022, relying on the written will drawn by Muturi Njoroge & Company Advocates.

In a twist, on September 27, 2022, Antony—listed as the first objector—filed an objection asserting that he was a legitimate son of the deceased who had been disinherited.

He sought to be enjoined as a beneficiary. On July 21, 2023, Raymond filed summons seeking to invalidate the will.

The trial magistrate in Gatundu initially found the will valid: it was in writing, had witnesses, and bore the deceased’s thumbprint. The court also ruled that the Juja properties mentioned in the will were not being newly bequeathed, but were simply recognising gifts the deceased had already distributed during his lifetime.

Raymond and several objectors saw something more sinister.

Appeal grounds

They filed an appeal at the High Court in Thika, insisting the will was the product of a mind in decline, clouded by dementia, manipulated by a dominant son and fundamentally mistaken about what property the old man actually owned.

Raymond and his two sisters, Wathoni and Wangui, had one explosive piece of evidence: the will purported to distribute land that no longer belonged to the deceased at all.

Search certificates showed that parcels JUJA/JUJA EAST BLOCK 1/2103 and 2105 had long been transferred—one to his son Raymond and another to Regina—about 18 years before the will was drawn.

In his appeal, Raymond told the High Court that his father could not have understood the extent of his property because he purported to bequeath land he did not own.

He did not stop at the land registers. He placed the deceased’s medical history before the court, including a CT brain scan report dated August 28, 2021—six months after the will—showing age-related cerebral atrophy and confusion.

“My late father was of unsound mind at the time of making the will, suffering from dementia and age-related cognitive decline,” Raymond stated in an affidavit.

The trial magistrate had brushed this aside as too remote in time to prove incapacity in February 2021. The High Court disagreed—strongly.

Justice Helene Namisi explained that this was not like malaria or a passing fever. “Brain involutional changes refer to cerebral atrophy—the shrinking of the brain. This is a chronic, progressive and irreversible condition… It is not a transient ailment that appears suddenly,” she ruled.

If the deceased was already confused, refusing to talk or feed, and had significant brain atrophy in August 2021, the court reasoned, then ‘it is medically and logically probable that the condition was present and progressing in February 2021’ when he signed the will.

Crucially, the court treated the inclusion of already-transferred parcels as a window into his mind.

“It is legally impossible for a testator to give, devise and bequeath property that is already vested in the beneficiary or in a third party… A testator of sound mind would know that he cannot bequeath his step-mother’s land to his daughter.”

That finding, the judge noted, reflects the test established in the landmark 1870 Banks v Goodfellow case from England, which has become the global benchmark for assessing whether a testator had the mental capacity to make a valid will.

Justice Namisi quoted the famous test: a testator must understand the act of making a will, the extent of their property, the claims of those who might expect to benefit, and must not be under a mental disorder or insane delusion that poisons their affections or perverts their sense of right.

In the Gakinya estate, the court held, the deceased failed the second limb: he did not truly understand the extent of the property he was disposing of.

Golden rule

Justice Namisi’s decision is also notable for bringing the so-called Golden Rule into sharp Kenyan focus.

First articulated in English courts but now relied upon locally, the rule states that where an aged or seriously ill person is making a will, an independent medical practitioner should examine them, certify their capacity at the time of execution and keep a record.

In the Gakinya case, there was no such medical certification at the time of signing, despite the deceased being in his mid-80s and already ailing.

The will was drawn by an advocate, witnessed at home and apparently organised by one of his sons, who stood to benefit most.

Justice Namisi was blunt that the lack of contemporaneous medical oversight, when viewed against later CT-scan evidence and glaring errors on property, was fatal to Joseph’s case.

The court held that the presumption of sanity under section 5(3) of the Law of Succession Act had been rebutted, and that Joseph failed to prove that the deceased was of sound mind when he executed the will.

Once doubt was raised about the testator’s mental state, the burden shifted to those relying on the will to prove that he understood what he was doing at the time he signed it.

Consequently, the will was declared invalid, null and void for lack of testamentary capacity, any grant of probate based on it was revoked, and the estate ordered to be administered as intestate under the default rules of the Law of Succession Act.

“The document purported to be the Last Will and Testament of the late Gakinya Kariuki alias John Gakinya Kariuki dated February 19, 2021 is hereby declared invalid, null and void for lack of testamentary capacity. Any Grant of Probate issued on the basis of the said invalid Will is hereby revoked. The estate of the Deceased shall be administered as an intestate estate in accordance with the provisions of the Law of Succession Act,” Justice Namisi ordered.

While revoking the will, the judge noted that Joseph was both sole executor and principal beneficiary, while other children who were allegedly dependants were excluded.

Additionally, the will’s witnesses were associates of Joseph rather than independent witnesses known to the deceased.

“Having found that the Deceased lacked testamentary capacity due to his inability to comprehend the extent of his property and his medical condition… it suffices to state that the confusion evident in the Will is consistent with a testator who was compliant but cognitively absent, possibly rubber-stamping a document prepared by others without full understanding,” she said.

“The Will dated February 19, 2021 cannot stand. It is the product of a mind that was not sound for testamentary purposes. The estate of the deceased must be distributed according to the rules of intestacy, which will ensure that all rightful children and dependants receive their fair share.”

The judge consequently remitted the matter to the Chief Magistrate’s Court at Gatundu for the filing of a fresh petition for letters of administration intestate.

An order of inhibition was issued against L.R. No KIGANJO/KIAMWANGI/1713 and any other estate assets, restraining all parties from selling, charging, leasing or otherwise disposing of the property until confirmation of the grant of letters of administration intestate.

National pattern

The Gakinya appeal is not an isolated skirmish. Across the country, judges are wrestling with similar questions: when does old age or dementia cross the line from vulnerability to legal incapacity? How should courts treat wills made in the twilight of life?

A similar line emerges in the estate of the late Kimetto Arap Kili, decided in 2023 by the High Court in Kapsabet. Siblings challenged their elderly father’s will.

Led by Hellen Cheptum Kebenei, they described a frail man, over 105 years old, visually impaired, ailing, unable to walk unaided, illiterate and innumerate, and unable to understand English or Kiswahili.

They argued he could not have understood, let alone signed, a will dated October 19, 2008, and pointed to the absence of any translation certificate. The will purported to distribute several parcels of land in Nandi and Uasin Gishu.

Justice Reuben found that, given his condition, Kimetto lacked testamentary capacity when he executed the will and invalidated it, stressing that a will is void only if, at the time of making it, the testator does not understand what a will is, the extent of their property, the expectations of potential beneficiaries, or acts under a disordered mind.

The court also reiterated the Golden Rule, warning lawyers that failing to involve a doctor when an elderly or seriously ill person makes a will can later prove disastrous.

By contrast, in the estate of Njenga Gituru, who died in 2017 aged 90, the will survived challenge.

His nine children from the first house sought to invalidate a 2012 will, relying on 2017 medical reports from PCEA Kikuyu Hospital diagnosing hyperglycaemia, hypertension and severe dementia.

Justice Stella Mutuku of Kajiado held that there was no evidence of mental illness in 2012 and that reports five years later could not retrospectively prove incapacity.

In Killian Ansei Mwoloi’s estate, the High Court in Makueni faced a burial dispute between two houses over a 2015 will that specified his preferred resting place.

Justice Mumbi Matheka found no cogent medical evidence to rebut the presumption of sanity under section 5 of the Law of Succession Act and upheld the will on capacity, though she ordered burial at his ancestral home.

In Eldoret, in the estate of Isaac Thiongo, the court went the other way, revoking probate after finding lack of testamentary capacity and improper execution, including a language barrier and defective formalities.

Parallel petitions under the Mental Health Act show families going to court even before succession disputes arise.

In one case, three children of a 77-year-old woman, codenamed EKK, obtained guardianship over her estate due to senile dementia.

In another, Justice Abigail Mshila in Kiambu appointed a daughter as guardian for her 80-year-old father with Alzheimer’s, noting he lacked capacity to manage his affairs.

Taken together, these cases sketch an emerging Kenyan doctrine on age, mental health and wills.

Some rulings reaffirm that the law presumes adults—even the very elderly—can decide how to distribute their property, and that families cannot use age alone to overturn unwelcome bequests.
Others show courts are ready to intervene where illness is proven to have undermined a testator’s understanding.