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When someone passes away, their last will and testament can carry significant emotional and financial meaning. It represents their final wishes and how they intended to distribute their estate. However, disputes can arise when a family member or beneficiary believes that the person who made the will did not have the mental capacity to do so.
At Faber LLP in Edmonton, Alberta, we regularly assist clients with providing guidance on clear wills and responding to challenges. Understanding how to demonstrate that a person was of sound mind is essential. This guide explains what testamentary capacity means, why wills are challenged, how to gather strong evidence, and what steps can be taken in advance to reduce the risk of a dispute.

What is Testamentary Capacity?

In the context of wills, the older phrase “sound mind and memory” is now referred to in law as testamentary capacity. In Alberta, a person must understand what they are doing at the time they make their will. This capacity is assessed based on several key elements.
The person making the will (the testator) must:
In Alberta, the Wills and Succession Act requires that the testator have mental capacity at the time the will is signed.
It is important to note that a diagnosis such as dementia or cognitive decline does not automatically mean a person lacks testamentary capacity. Capacity can fluctuate. The critical question is whether the person met the criteria above at the time the will was executed.

Why Wills Get Challenged on Capacity Grounds

Challenges to wills can be emotionally driven and legally complex. In Alberta, a will may be contested for reasons such as lack of capacity, undue influence, fraud or forgery, or failure to provide for certain dependents.
When a will is challenged on the basis of capacity, the argument is usually that the testator did not understand the nature or effect of the will at the time it was signed, or that their judgment was impaired due to illness, cognitive decline, or improper influence.
For example, in McKay v Olsen, 2024 ABCA 90, medical records showed mild dementia and inconsistent decision making during the final months of the testator’s life. However, the Alberta Court of Appeal confirmed that this evidence was not enough to overcome the starting point in law: that a properly executed will is presumed valid.
This presumption of validity means the law begins with the assumption that the testator had capacity when the will was signed. It is the responsibility of the person challenging the will to prove otherwise.
Whether you are defending a will as an executor or considering a challenge, understanding what evidence is necessary, and how to present it, is essential.

How to Prove Mental Capacity: Evidence and Documentation

If there is a possibility that a will may be challenged on capacity grounds, it is important to create a clear record of the testator’s understanding at the time the will is made. The stronger the documentation, the more likely the will is to withstand scrutiny.
Having a lawyer prepare the will helps ensure the correct formalities are followed, including signatures and witnesses. While proper formalities do not guarantee capacity, they reduce the risk of technical issues and provide reliable professional notes and observations.
A medical assessment from around the time the will was signed can be powerful evidence. A physician or specialist can comment on memory, reasoning, awareness of property, and understanding of relationships. A diagnosis of dementia or cognitive decline is not automatically disqualifying. The question is the person’s capacity at the time the will was executed.
Witnesses who were present when the will was signed, or who heard the instructions leading to its preparation, can provide valuable observations. They may speak to:
These firsthand impressions can be highly persuasive.
A lawyer or estate planning professional should record key details, such as:
Documented notes or correspondence from the planning process can be decisive evidence later.
Certain situations increase the likelihood of a challenge, such as:
Recognizing these factors in advance allows additional steps to strengthen documentation.
If possible, a will should be signed during a period of clarity. Avoid executing the will immediately after surgery, during active infection or confusion, or when medication affects awareness. Capacity can vary day to day. Choosing the right time improves the quality of evidence.

What to Do If the Will Is Challenged

Even when a will has been carefully prepared, disputes can still arise. If a challenge is made, or you suspect one may be coming, the steps taken early can significantly affect the outcome.
If You Are the Personal Representative (Executor), gather key documents promptly, including:
If You Are Considering a Challenge
Consider Resolution Options
Remember Capacity Is Assessed at the Time of Signing
If You Are Defending the Will, demonstrate that the process was sound. Show that:
Wills and estate law is detailed and continues to evolve. Working with counsel who understands Alberta statutes and case law is important for both defending and challenging a will effectively.

How to Reduce the Risk of a Capacity Challenge

As an Edmonton, Alberta based estate planning firm, Faber LLP helps clients plan ahead to reduce the likelihood that a will is challenged on the basis of mental capacity. While no plan can eliminate all risk, certain practical steps can make the testator’s intentions clearer and better supported.
By taking these steps, the risk of a successful challenge is significantly reduced. When a will is prepared carefully, with respect for the testator’s wishes and awareness of their health and circumstances, it is far more likely to be honored.

Why This Matters in Alberta

In Alberta, the legal system places strong weight on the intention of the testator, but also protects against documents that reflect impairment, undue influence or improper execution. As one source puts it, “wills are commonly challenged on the grounds of the testator’s mental capacity and may be invalidated if a lack of mental capacity is proven.” (mergenlaw.com) 
We operate in Edmonton and across Alberta and have insight into how the Provincial courts treat capacity challenges. The geographic and legislative context matters. Being aware of Alberta’s statute-law and case-law helps us tailor advice that is practical for you.

In Summary

At Faber LLP, we assist families in preparing clear, well-supported wills and in navigating disputes when they arise. Whether you are planning ahead or responding to a challenge, you do not need to manage the process alone. We are here to help ensure your loved one’s wishes are respected and their legacy protected.

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