Lack of Testamentary Capacity: What Must Be Proven?

Allegations of lack of testamentary capacity are among the most common grounds for challenging a will in Ontario. These cases often arise in emotionally charged circumstances: a will signed late in life, a diagnosis of dementia, an unexpected disinheritance, or a dramatic departure from a long-standing estate plan.

Despite how frequently these claims are made, the legal threshold for proving lack of capacity is both specific and demanding. It is also frequently misunderstood. A medical diagnosis alone is not enough, nor is advanced age. The court’s task is a focused legal inquiry: did the testator have testamentary capacity at the precise time the will was executed?

Below, I will set out what must be proven, how courts assess medical evidence, and the red flags that frequently lead to litigation when a testator’s capacity is at question.

The Governing Legal Test: Banks v. Goodfellow

Ontario courts continue to apply the classic test from Banks v. Goodfellow 1870, a decision that remains the foundation of testamentary capacity law across common law jurisdictions.

Under the test set forth in Banks v. Goodfellow, a person making a will must understand the nature and effect of the act they are undertaking. In practical terms, they must appreciate that they are creating a document that will govern the distribution of their property upon death. They must also have a general understanding of the nature and extent of their assets, not precise dollar figures, but an appreciation of what they own.

Equally important, the testator must understand the claims of those who might reasonably expect to benefit from the estate, such as a spouse or children. Finally, they must not suffer from a delusion or mental disorder that influences the distribution of their assets. A mental health diagnosis does not automatically invalidate a will, but the critical question is whether any impairment affected the testamentary decisions themselves.

Testamentary capacity is both task-specific and time-specific. A person may lack capacity for complex financial management yet still possess the narrower capacity required to make a will (check out Cassandra Martino’s blog on the different levels of capacity here). Conversely, capacity can fluctuate, particularly in cases involving dementia or delirium. The relevant moment is the time of execution.

The Presumption of Capacity and Suspicious Circumstances

In Ontario, a properly executed will is presumed valid. The party challenging it bears the initial burden of putting forward evidence that raises suspicious circumstances. These circumstances may include significant cognitive decline, abrupt changes in testamentary intentions, or the involvement of a beneficiary in the preparation of the will.

If suspicious circumstances are established, the evidentiary burden shifts. The propounder of the will must then prove, on a balance of probabilities, that the testator had capacity. This burden-shifting framework is often decisive in estate litigation and underscores the importance of the surrounding factual context.

The Role of Medical Evidence

Medical records frequently play a central role in capacity disputes, but they rarely determine the issue on their own. Courts draw a careful distinction between cognitive impairment and legal incapacity. A diagnosis of Alzheimer’s disease or another form of dementia does not automatically mean a person lacked testamentary capacity. Many individuals with early or moderate cognitive impairment can still satisfy the Banks v. Goodfellow criteria.

That said, medical evidence close in time to the execution of the will is highly relevant. Physician notes, hospital charts, geriatric assessments, and memory clinic reports can shed light on the testator’s cognitive functioning. Courts will look closely at contemporaneous observations: confusion, memory deficits, disorientation, or conversely, indications that the individual was alert and oriented. Because capacity can fluctuate, records from weeks or even days surrounding execution can carry significant weight.

For example, imagine an elderly man who meets with his lawyer on Monday to sign a new will. During the meeting, he clearly explains that he wants to leave his estate equally to his three children. He understands that he owns a house and some investments, and he knows the will controls what happens to his property when he dies. He answers questions appropriately and appears to understand what he is doing. The next day, he goes to his doctor and is diagnosed with early-stage dementia. That diagnosis does not automatically mean he lacked capacity when he signed the will the day before. Dementia can develop gradually, and many people in the early stages are still capable of understanding their decisions. The key legal question is not whether he was later diagnosed with dementia, but whether he had the required understanding at the time he signed the will.

Retrospective Capacity Assessments

In many contested estates, no formal capacity assessment was performed when the will was signed. Litigation then proceeds with the benefit of hindsight. Parties frequently retain experts — often geriatric psychiatrists — to conduct retrospective capacity assessments.

These experts do not examine the deceased. Instead, they review the available documentary record: medical charts, the drafting solicitor’s file, witness affidavits, and examination transcripts. From this material, they form an opinion about whether the testator likely met the legal test at the relevant time.

The strength of a retrospective opinion depends heavily on the quality of the underlying evidence. Sparse solicitor’s notes and limited medical documentation can weaken an expert’s conclusions. Detailed contemporaneous records, by contrast, can be powerful evidence either supporting or undermining the validity of the will.

Patterns That Trigger Closer Scrutiny

While each case turns on its own facts, certain recurring patterns tend to attract judicial scrutiny. A dramatic departure from a prior estate plan, particularly where close family members are disinherited, often raises questions. So too does the emergence of a new beneficiary late in life, especially where that individual was involved in arranging meetings or communicating with the drafting lawyer.

Isolation from family members, advanced cognitive decline, or the execution of a will shortly before death may also contribute to a finding of suspicious circumstances. None of these factors automatically invalidates a will. Rather, they shape the evidentiary landscape and determine whether the propounder must affirmatively prove capacity.

Drafting Solicitors and Litigation Risk

From a litigation perspective, the drafting solicitor’s file frequently becomes central evidence. Courts rely heavily on contemporaneous notes describing the testator’s instructions, demeanor, and responses to questions.

Red flags for drafting lawyers include advanced age coupled with observable memory issues, radical changes to a longstanding estate plan, recent medical diagnoses affecting cognition, and the presence or involvement of beneficiaries in the instructions process. Urgency without clear explanation — particularly in the context of medical crisis — can also increase risk.

Careful practice management can significantly reduce the likelihood of a successful challenge. Meeting alone with the testator, asking open-ended questions, documenting reasoning for changes, and considering a contemporaneous capacity assessment where appropriate are all protective steps. In litigation, detailed notes often become the most persuasive non-medical evidence before the court.

Capacity and Undue Influence

Claims of lack of capacity are frequently advanced alongside allegations of undue influence. Although legally distinct, they often arise from the same factual matrix. A vulnerable testator may technically meet the Banks v. Goodfellow test yet still have been coerced. Conversely, a person suffering from cognitive decline may lack capacity even in the absence of overt pressure.

Understanding how these doctrines intersect is critical when assessing litigation strategy and evidentiary priorities.

Conclusion

Will challenges based on lack of capacity require careful, evidence-driven analysis. The legal threshold is precise. The court is not concerned with whether the testator made a fair or reasonable decision, but whether they satisfied the Banks v. Goodfellow criteria at the time the will was executed.

In practice, these cases often turn on contemporaneous documentation, medical records, and the quality of the drafting solicitor’s file. For estate trustees, beneficiaries, and counsel alike, early strategic assessment is essential. Once estate assets are distributed, remedies become more complex and costly.

Where capacity is in doubt, timing and evidence are everything.