Today’s blog was written by Christopher Cook, Student-At-Law at de VRIES LITIGATION LLP
In some common law jurisdictions, there exists a fascinating (but rarely applied) legal doctrine called “patent mistake.” This doctrine applies in the context of applications for probate. When asked to probate a will, the court’s task is to determine whether the will in question really is the deceased’s last will and testament. Naturally, this inquiry requires the court to ascertain whether the deceased knew and approved of the contents of the will.
According to some authorities, because of the knowledge and approval requirement, a court may refuse to admit a will to probate—either in whole or in part—if it was induced by a mistake. However, only certain types of mistake will give rise to a court’s refusal to probate a will. One such type of mistake is a “patent mistake,” which has been described as a mistake about an existing fact. In short, if it can be demonstrated that the will or testamentary gift was made in reliance on a mistake of fact, the disposition will be inoperative, meaning the will (or part of it) should be denied probate.
The doctrine of patent mistake dates back centuries. The first reported decision involving the doctrine is Campbell v French, (1797) 3 Ves. Jun. 321. In Campbell v French, the testator made a new will revoking a gift to his late sister’s grandchildren because he believed the grandchildren had died. It turned out that that testator was wrong; the grandchildren were very much alive. Because the revocation was ultimately based on false information, the Court held the revocation to be ineffective.
More recently (but still nearly a century ago), the doctrine of patent mistake was applied in Wright Estate, 1937 CarswellSask 62 (Sask. King’s Bench). In Wright Estate, the testator, who was living in Canada, believed that his wife and daughter, who were living in England, had died. Accordingly, the testator left his estate to a non-family member, noting in his will that his decision was because “I have no living relations.” Like in Campbell v French, it turned out that the testator’s belief was a mistake of fact. His wife and daughter were still alive. Because of the testator’s factual mistake, the Court held that the gift to the non-family member was inoperative, and ordered the estate to pass to the wife and daughter.
Does the doctrine of patent mistake apply in Ontario today? For now, the answer appears to be no. In Cavanagh et al v Sutherland et al, 2019 ONSC 2186, the testatrix’s disinherited daughter objected to the issuance of a certificate of appointment of estate trustee. The daughter argued that her disinheritance was premised on the testatrix’s false belief that the daughter had extorted $65,000 from the testatrix’s husband. The daughter claimed that the $65,000 sum actually constituted repayment of a loan that she had given the testatrix’s husband many years prior. According to the daughter, the will was invalid because of the testatrix’s fundamental factual error. Ultimately, because the Court found that the testatrix had not made a mistake of fact, it had no reason to consider the daughter’s argument. However, at para. 17, the Court said in passing:
The sparse jurisprudence relied on by Ms. Sutherland to support her proposition of law that a testator’s disposition is ineffective if it is contingent upon the testator’s mistake about a material fact, does not include any resort to this concept by an Ontario court. Counsel for Ms. Sutherland has advised that he is aware of no Ontario case in which this proposition has been applied.
Although the Court in Cavanagh declined to endorse the daughter’s argument based on the doctrine of patent mistake, the Court appears not to have rejected the doctrine outright. Arguably, it is an open question whether the doctrine applies in Ontario—a question that will hopefully be answered one day.
 For a more detailed discussion on patent mistake, see: James MacKenzie (Editor), Feeney’s Canadian Law of Wills, 4th Ed., § 3.23-3.27; Oosterhoff on Wills and Succession (Toronto: Carswell, edition quoted not specified) at page 218, cited in Foster v Boone, 2010 NBCA 11 (CanLII) at para. 16.
 In re Wright Estate, 1937 CarswellSask 62 (Sask. King’s Bench) at para. 3.