How do you prove undue influence in a will challenge in Ontario?

Proving undue influence in an Ontario will challenge is notoriously difficult. Courts require that the person challenging the will show that the influence exerted over the testator was so overpowering that it essentially replaced the testator's own free will with the influencer's wishes. Normal persuasion, appeals to affection, or even expressing strong preferences does not rise to the level of undue influence in law.

There is rarely direct evidence of undue influence — no one conducts coercion in front of witnesses. Courts therefore look at a pattern of circumstantial evidence: was the testator vulnerable due to age, illness, or cognitive decline? Was the person who benefited in a position of trust or authority over the testator? Was the testator isolated from other family members? Did the will depart significantly from earlier wills or the testator's expressed intentions? Did the beneficiary play an active role in arranging for the will to be made?

In some circumstances — particularly where a dependent relationship or position of trust exists — a limited presumption of undue influence may arise, shifting the burden to the beneficiary to show the transaction was legitimate. However, this is more commonly applied to inter vivos transactions than to wills.

Gathering evidence early, including medical records, financial records, and testimony from people who knew the testator, is critical.