Testamentary capacity and undue influence frequently arise in Ontario will challenges because both concern whether a will genuinely reflects the deceased’s independent intentions. They are different legal issues, however: capacity concerns whether the testator had the mental ability to make the will, while undue influence concerns whether another person improperly displaced the testator’s free decision-making.
Testamentary capacity focuses on the testator’s ability to understand the will.
A capacity dispute may arise where the deceased was experiencing cognitive decline, serious illness, confusion, dementia, or other circumstances that raise questions about whether they understood the nature and effect of the will they were making.
The evidence may include medical records, the drafting solicitor’s file, witness evidence, previous wills, and information about the deceased’s condition and behaviour around the time the challenged will was executed. A diagnosis or advanced age does not automatically establish incapacity. The issue is the testator’s capacity at the legally relevant time.
Undue influence focuses on whether the will was made freely.
A person may have testamentary capacity but still be subjected to pressure, coercion, manipulation, or control by another person. ME Law’s existing estate-litigation material identifies evidence such as witness testimony, medical evidence showing vulnerability, financial records, sudden changes to a will, and patterns of isolation or dependency as potentially relevant in undue-influence disputes.
For a detailed discussion of this practice area, see Capacity & Undue Influence Litigation.
Why can the two issues appear in the same case?
Vulnerability may be relevant to both allegations. For example, cognitive decline may raise a capacity question while also making a testator more dependent on a caregiver, relative, or other person who participated in a significant change to the estate plan.
That overlap does not mean vulnerability proves either ground. The evidence must be assessed to determine whether the concern is lack of capacity, undue influence, both, or neither.
A substantial last-minute change, the exclusion of a previous beneficiary, increased dependency, or a beneficiary’s unusual involvement in arranging the new will may justify closer investigation, but the surrounding circumstances matter.
For the complete range of possible legal grounds, see What are the legal grounds for contesting a will in Ontario?.
How does ME Law assess these cases?
ME Law reviews the evidence surrounding the preparation and execution of the will rather than treating an unexpected inheritance result as proof of wrongdoing. This can include the challenged will, earlier wills, medical evidence, the drafting solicitor’s records, communications, financial information, and witness evidence.
If the evidence supports a formal estate dispute, Ontario contentious estate proceedings may engage Rule 75 of the Rules of Civil Procedure. Depending on the procedural stage, a Notice of Objection (Form 75.1) may also be relevant where an application for a Certificate of Appointment of Estate Trustee is pending. Ontario Court Services identifies Form 75.1 as the Notice of Objection used under Rule 75.
For the broader threshold question, see Can I contest a will in Ontario?
Contact ME Law if you are concerned that a will may have been affected by lack of testamentary capacity or undue influence.