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BACK TO SCHOOL: Solicitors’ Negligence – Causation

Sep 21, 2020

By Sheila Morris, Wills and Estates Litigator

Image: Sheila Morris, Wills and Estates LawyerWith the “back to school” season upon us (although it looks and feels very different this year), it is a good time to hit the books and review the latest developments in solicitors’ negligence. This four-part series will examine the essential elements of solicitors’ negligence with a specific focus on will-drafting lawyers. Cram now, and ace the test later!

Causation: The Legal Test

The third installment in this series examines the element of causation. The starting point for causation is the “but for” test. It is a short-hand test to question whether, but for the lawyer’s negligence, the loss would have occurred.[1] The burden of proof is a balance of probabilities.[2] The test will only be made out where there is a substantial connection between a party’s loss and the lawyer’s conduct. This ensures that a lawyer will not be held liable for a plaintiff’s injuries when they are caused by factors unconnected to the lawyer, and/or are caused by someone else.[3] A plaintiff does not need to prove causation with scientific precision.[4]

When the loss is purely economic, there must be a close (proximate) relationship between the alleged wrongdoer (the tortfeasor) and the victim. Both English and Canadian jurisprudence have sought to define a “proximate relationship”. The Court of Appeal for British Columbia posed it as a question of whether, in carrying out their duties to a client, a lawyer is under an obligation to be mindful of the [plaintiff’s] interests.[5] The Supreme Court of Canada has described a proximate relationship as one that is “close and direct.”[6] A proximate relationship requires something more than just foreseeability of harm and an absence of a reason for denying liability. [7]

Causation in the Estates Context

In the estates context, and depending on whether the plaintiff is a Third Party Beneficiary[8] or a Former Beneficiary[9] (as discussed in a previous article), the plaintiff must demonstrate that the drafting lawyer caused them either to be deprived of a gift that the testator intended to give, or caused the estate to have to participate in litigation.

It is important to remember that a claim against a drafting lawyer is not necessarily predicated on the outcome of a will challenge.[10] They are two separate lines of inquiry. So, although someone may be successful in setting aside a will, it does not automatically mean that the drafting lawyer is at fault. Recall from my article on standard of care that the relevant question is not whether the testator was in fact capable of making a will, but whether a reasonable and prudent lawyer could have concluded that they did not.[11] Therefore, if a drafting lawyer has met the requisite standard of care, they have discharged their duty to the client, even if the decision proves to be disastrous.[12]

Once a plaintiff has met the burden of showing a lawyer’s breach of fiduciary duty, the burden lies with the lawyer to prove that the client was not injured by their negligence or breach of duty.[13]


Sheila Morris is a skilled wills and estates litigator, litigating will challenges, unjust enrichment claims, dependent support claims, and power of attorney disputes at various levels of courts across Ontario. For questions about solicitors’ negligence or wills and estates issues, contact Sheila Morris at

To read Parts 1-4, click on the links below:

[1] Hill v Hamilton-Wentworth (Regional Municipality) Police Services Board, 2007 SCC 41 (S.C.C.) at para 93

[2] Resurfice Corp v Hanke 2007 SCC 7 (S.C.C.) at para 22

[3] Snell v. Farrell, [1990] 2 S.C.R. 311, as cited in Michiels v Kinnear 2011 ONSC 3826 (Ont. S.C.J.) (“Michiels v Kinnear”), at para 168 

[4] Michiels v Kinnear at para 168

[5] Dhillon v Jaffer 2012 BCCA 156 (B.C. C.A.) (“Dhillon v Jaffer”), at para 33

[6] Cooper v Hobart 2001 SCC 79 (S.C.C.) at para 31

[7] Dhillon v Jaffer, at para 29

[8] As defined in Graham v Bonnycastle 2004 ABCA 270 (Alta C.A.) (“Graham v Bonnycastle”) at para 17 as “the intended beneficiary under a will, who does not, as a result of the solicitor's negligence, receive a benefit which the testator intended to grant”

[9] As defined in Graham v Bonnycastle at para 31 simply as “beneficiaries under a former will”

[10] Brown Estate, Re 2001 CarswellOnt 1333 (Ont. S.C.J.) at para 20

[11] Hall v. Bennett Estate (2003), 227 D.L.R. (4th) 263 (Ont. C.A.) at para 12

[12] Folland v Reardon 2003 CarswellOnt 1087 (Ont. C.A.) at para 44

[13] Michiels v Kinnear at para 169